The Annals of Occupational Hygiene

About the journal

Publisher: Oxford University Press
Published: 1958–2016, England
Language: English, French
ISSN: 0003-4878 (print), 1475-3162 (electronic)
Continued by: Annals of Work Exposures and Health
Its record in the NLM Catalog

2010s

Airborne Asbestos Exposures from Warm Air Heating Systems in Schools. G.J. Burdett, K. Dewberry, J. Staff. 2016;60(1):27-39. PubMed · Publisher · Free full text

Abstract

The aim of this study was to investigate the concentrations of airborne asbestos that can be released into classrooms of schools that have amosite-containing asbestos insulation board (AIB) in the ceiling plenum or other spaces, particularly where there is forced recirculation of air as part of a warm air heating system. Air samples were collected in three or more classrooms at each of three schools, two of which were of CLASP (Consortium of Local Authorities Special Programme) system-built design, during periods when the schools were unoccupied. Two conditions were sampled: (i) the start-up and running of the heating systems with no disturbance (the background) and (ii) running of the heating systems during simulated disturbance. The simulated disturbance was designed to exceed the level of disturbance to the AIB that would routinely take place in an occupied classroom. A total of 60 or more direct impacts that vibrated and/or flexed the encapsulated or enclosed AIB materials were applied over the sampling period. The impacts were carried out at the start of the sampling and repeated at hourly intervals but did not break or damage the AIB. The target air volume for background samples was ~3000 l of air using a static sampler sited either below or ~1 m from the heater outlet. This would allow an analytical sensitivity (AS) of 0.0001 fibres per millilitre (f ml(-1)) to be achieved, which is 1000 times lower than the EU and UK workplace control limit of 0.1 f ml(-1). Samples with lower volumes of air were also collected in case of overloading and for the shorter disturbance sampling times used at one site. The sampler filters were analysed by phase contrast microscopy (PCM) to give a rapid determination of the overall concentration of visible fibres (all types) released and/or by analytical transmission electron microscopy (TEM) to determine the concentration of asbestos fibres. Due to the low number of fibres, results were reported in terms of both the calculated concentration and the statistically relevant limits of quantification (LOQ), which are routinely applied. The PCM fibre concentrations were all below the LOQ but analytical TEM showed that few of the fibres counted in the background samples were asbestos. The background TEM asbestos concentrations for the individual samples analysed from all three schools were at or below the AS, with a pooled average below the LOQ (<0.00005 f ml(-1)). At the two CLASP schools, there was no significant increase in the airborne amosite concentration in the classrooms during simulated disturbance conditions. At the third school, four of the five classrooms sampled gave measurable concentrations of amosite by TEM during simulated disturbance conditions. The highest concentration of amosite fibres countable by PCM was 0.0043 f ml(-1) with a pooled average of 0.0019 f ml(-1). The air sampling strategy was effective and worked well and the results provide further important evidence to inform the sampling and management of asbestos in schools.

© The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Differential Counting of Asbestos Using Phase Contrast and Fluorescence Microscopy. T. Nishimura, M. Alexandrov, T. Ishida, et al. 2016;60(9):1104-1115. PubMed · Publisher

Abstract

Considering the increasing use of various asbestos substitutes, asbestos risk management in many industries may require accurate techniques for detecting and distinguishing asbestos from non-asbestos fibers. Using fluorescently labeled asbestos-binding proteins, we previously developed a novel method for detection and counting of asbestos fibers under fluorescence microscopy (FM). This method can provide speedy, on-site detection and identification of the asbestos fibers and has higher sensitivity than phase contrast microscopy (PCM). However, current asbestos exposure limits are derived from risk assessments based on epidemiological studies that were conducted using PCM fiber counts. Therefore, the sensitivity of asbestos testing should be maintained at PCM level to properly assess compliance with these limit values. Here, we developed and tested a novel application of FM as a differential counting method that complements PCM analysis and is fully compatible with the PCM-based epidemiological data. In the combined PCM-FM method, the fluorescent asbestos-binding probe is applied prior to filter clearing. The method makes it possible to easily switch between two microscopic techniques while analyzing the same fields of view: PCM is used for counting fibers, and FM for differentiating asbestos from non-asbestos fibers. Using airborne dust samples from demolition sites in Japan, we compared PCM-FM with scanning electron microscopy (SEM)-based differential counting method. Statistical analysis indicated a slight conservative bias of PCM-FM method, combined with relatively high variability across the full range of fiber concentrations in our sample set. Using correlative microscopy, we also evaluated the specificity of FM staining, which is a potential cause of variability between the two methods. The energy-dispersive X-ray analysis indicated that ~95% of fluorescently stained fibers in the demolition site samples were correctly identified as asbestos. While further research is needed to fully clarify the causes of variability between FM- and SEM-based differential counting, PCM-FM could be used for rapid and selective detection of asbestos fibers in field samples.

© The Author 2016. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Estimating Lifetime Asbestos Exposure in Patients With Idiopathic Pulmonary Fibrosis. C.M. Barber, R.E. Wiggans, D. Fishwick. 2016;60(5):649-50. Letter · Comment PubMed · Publisher · Free full text
Estimating Occupational Exposure to Asbestos in Australia. M. Kottek, D.J. Kilpatrick. 2016;60(4):531-2. Letter · Comment PubMed · Publisher

Summary

In this letter, two Australian authors commented on the asbestos job-exposure matrix (AsbJEM) published by van Oyen et al. (2015), to which they had contributed unpublished dust measurements. They noted that Australian asbestos exposure limits predated 1964. Victoria adopted a ceiling standard of 5 million particles per cubic foot in 1945, and this level was adopted nationally as an 8-h time-weighted average (TWA) in 1960. They agreed that AsbJEM's estimated annual average exposures appeared very low but argued that some estimates did not 'make sense'. AsbJEM gave cumulative exposures of 2.3 f ml−1·y for a boilermaker and 3.6 f ml−1·y for a fitter who spent their entire working life in the power supply industry (1943–1986). The authors considered these figures inconsistent with the many asbestosis cases they had seen in these workers, and with the 79 f ml−1·y average estimated for metalworkers in a German power supply company. Drawing on work and exposure histories from over 2000 people with asbestos-related disease, they suggested that the expert panel had severely underestimated how often peak exposures occurred. They also questioned the assumption that each peak lasted 15 min, citing a simulation of pipe fitter tasks that recorded short-term exposures of 83 f ml−1 and an 8-h TWA of 86 f ml−1. They expected AsbJEM to distinguish high- and low-exposure jobs but doubted it would improve attribution of individual cases to past exposures. Both authors had given expert evidence for plaintiffs and defendants in asbestos litigation.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Factors Associated With Non-compliance of Asbestos Occupational Standards in Brake Repair Workers. M.F. Cely-García, F.C. Curriero, M. Giraldo, et al. 2016;60(8):1020-35. PubMed · Publisher

Abstract

Asbestos and non-asbestos containing brake products are currently used in low- and middle-income countries like Colombia. Because brake products are distributed detached from their supports, they require manipulation before installation, which release fibers and expose workers. Previous studies of our research group have documented exposures in excess of the widely accepted 0.1 f/cm(3) exposure guideline. The aim of this study is to identify factors associated with non-compliance of the 8-h time weighted average (TWA) 0.1 f/cm(3) asbestos occupational limit among brake mechanics (i.e. riveters). Eighteen brake repair shops (BRS) located in Bogotá (Colombia) were sampled during 3 to 6 consecutive days for the entire work-shift. Personal and short-term personal samples were collected following NIOSH methods 7400 and 7402. Longitudinal based logistic regression models were used to determine the association between the odds of exceeding the 8-h TWA 0.1 f/cm(3) asbestos occupational limit and variables such as type of tasks performed by workers, workload (number of products manipulated daily), years of experience as riveters, and shop characteristics. These models can be used to estimate the odds of being currently or historically overexposed when sampling data do not exist. Since the information required to run the models can vary for both retrospective and current asbestos occupational exposure studies, three models were constructed with different information requirements. The first model evaluated the association between the odds of non-compliance with variables related to the workload, the second model evaluated the association between the odds of non-compliance with variables related to the manipulation tasks, and the third model evaluated the association between the odds of non-compliance with variables related with both the type of tasks performed by workers and the workload. Variables associated with the odds of non-compliance included conducting at least one manipulation activity with beveling and grinding of asbestos and non-asbestos containing brake products during the work shift, the location of the worker in the shop during non-manipulation activities, cleaning activities of the manipulation area, the years of experience working as riveters, and the number of asbestos and non-asbestos containing brake products manipulated daily. These models could be useful for current and retrospective occupational studies, in determining the odds of non-compliance of the asbestos occupational limit among brake mechanics.

© The Author 2016. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Mesothelioma among Motor Vehicle Mechanics: An Updated Review and Meta-analysis. D.H. Garabrant, D.D. Alexander, P.E. Miller, et al. 2016;60(1):8-26. Meta-analysis · Systematic review PubMed · Publisher

Abstract

Background: We published a meta-analysis of the association between work as a motor vehicle mechanic and mesothelioma in 2004. Since then, several relevant studies on this topic have been published. Thus, to update the state-of-the-science on this issue, we conducted a new systematic review and meta-analysis.

Methods: A comprehensive PubMed literature search through May 2014 was conducted to identify studies that reported relative risk estimates for mesothelioma among motor vehicle mechanics (in general), and those who were engaged in brake repair (specifically). Studies were scored and classified based on study characteristics. Random-effects meta-analyses generated summary relative risk estimates (SRREs) and corresponding 95% confidence intervals (CI). Heterogeneity of results was examined by calculating Q-test P-values (P-H) and I (2) estimates. Sub-group and sensitivity analyses were conducted for relevant study characteristics and quality measures.

Results: Ten case-control studies, one cohort study, and five proportionate mortality ratio (PMR)/standardized mortality odds ratio (SMOR) studies were identified and included in the quantitative assessment. Most meta-analysis models produced SRREs below 1.0, and no statistically significant increases in mesothelioma were observed. The SRRE for all studies was 0.80 (95% CI: 0.61-1.05) with significant heterogeneity (P-H <0.001, I (2) = 62.90). A similar SRRE was observed among the five Tier 1 studies with the highest quality ratings (SRRE = 0.76, 95% CI: 0.46-1.25), with no heterogeneity among studies (P-H = 0.912, I (2) = 0.00). Meta-analysis of the Tier 2 (n = 5) and Tier 3 (n = 6) studies resulted in SRREs of 1.09 (95% CI: 0.76-1.58) and 0.73 (95% CI: 0.49-1.08), respectively. Restricting the analysis to Tiers 1 and 2 combined resulted in an SRRE of 0.92 (95% CI: 0.72-1.29). The SRRE specific to brake work (n = 4) was 0.64 (95% CI: 0.38-1.09).

Conclusions: This meta-analysis of the epidemiologic studies provides evidence that motor vehicle mechanics, including workers who were engaged in brake repair, are not at an increased risk of mesothelioma.

© The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Response to Kay Teschke. Re: Mesothelioma among Motor Vehicle Mechanics: An Updated Review and Meta-analysis. D.H. Garabrant, D.D. Alexander, P.E. Miller, et al. 2016;60(8):1036-7. Letter · Comment PubMed · Publisher

Summary

In this letter, the authors of a 2016 meta-analysis of mesothelioma among motor vehicle mechanics replied to a letter by Dr Kay Teschke. They stated that Dr Teschke had no criticisms of their paper but had focused on how epidemiological evidence should be interpreted in legal cases, which they considered beyond the scope of their paper. They said their meta-analysis asked whether motor vehicle mechanics and brake repair workers were at increased risk of mesothelioma. It did not ask whether these workers were the right setting in which to study the risks of chrysotile. They listed possible reasons why no increased risk was observed. These included low cumulative chrysotile exposure, absence of commercial amphiboles, low potency of chrysotile, short-fiber chrysotile in friction materials that degrades into shorter fibers and forsterite, binding of fibers in resin, and part-time brake work. They argued that studies classifying workers by occupation remain informative even without full exposure characterization. They noted that sub-analyses by duration of work and by brake work also did not show increased risk. They concluded that the epidemiology does not support a conclusion that motor vehicle mechanics and brake repair workers are at increased risk of mesothelioma. Several authors declared legal testimony or consultancy on behalf of automotive and brake-related companies.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Response to Kottek and Kilpatrick, 'Estimating Occupational Exposure to Asbestos in Australia'. S. Peters, S.C. van Oyen, H. Alfonso, et al. 2016;60(4):533-5. Letter · Comment PubMed · Publisher
SYN-JEM: A Quantitative Job-Exposure Matrix for Five Lung Carcinogens. S. Peters, R. Vermeulen, L. Portengen, et al. 2016;60(7):795-811. PubMed · Publisher

Abstract

Objective: The use of measurement data in occupational exposure assessment allows more quantitative analyses of possible exposure-response relations. We describe a quantitative exposure assessment approach for five lung carcinogens (i.e. asbestos, chromium-VI, nickel, polycyclic aromatic hydrocarbons (by its proxy benzo(a)pyrene (BaP)) and respirable crystalline silica). A quantitative job-exposure matrix (JEM) was developed based on statistical modeling of large quantities of personal measurements.

Methods: Empirical linear models were developed using personal occupational exposure measurements (n = 102306) from Europe and Canada, as well as auxiliary information like job (industry), year of sampling, region, an a priori exposure rating of each job (none, low, and high exposed), sampling and analytical methods, and sampling duration. The model outcomes were used to create a JEM with a quantitative estimate of the level of exposure by job, year, and region.

Results: Decreasing time trends were observed for all agents between the 1970s and 2009, ranging from -1.2% per year for personal BaP and nickel exposures to -10.7% for asbestos (in the time period before an asbestos ban was implemented). Regional differences in exposure concentrations (adjusted for measured jobs, years of measurement, and sampling method and duration) varied by agent, ranging from a factor 3.3 for chromium-VI up to a factor 10.5 for asbestos.

Conclusion: We estimated time-, job-, and region-specific exposure levels for four (asbestos, chromium-VI, nickel, and RCS) out of five considered lung carcinogens. Through statistical modeling of large amounts of personal occupational exposure measurement data we were able to derive a quantitative JEM to be used in community-based studies.

© The Author 2016. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Thinking about Occupation-Response and Exposure-Response Relationships: Vehicle Mechanics, Chrysotile, and Mesothelioma. K. Teschke. 2016;60(4):528-30. Letter PubMed · Publisher

Summary

The author, whose 1997 study was included as a 'tier 1' study in the 2016 meta-analysis by Garabrant et al. of mesothelioma among motor vehicle mechanics, addressed two questions about interpreting such evidence. First, she asked whether studies of vehicle mechanics and brake repair were appropriate settings to examine mesothelioma risk from chrysotile, since jobs and tasks act only as surrogates for exposure. In three studies in the meta-analysis that recorded brake repair separately, at least 34% of vehicle mechanics reported no brake repair work, and 12 of the 16 included studies examined only the vehicle mechanic job or broader categories. In the four studies reporting on brake repair, exposure occurred mostly long before 1980 and was likely intermittent. She argued that both the occupation and the task were poor surrogates, that associations were likely attenuated by subjects with background or low exposure, and that studies measuring chrysotile exposure would be more reliable. Second, she argued that evidence of an elevated occupation–disease association should not be required to decide whether a person's disease arose from workplace exposure, because exposures vary within jobs and not every job can be studied. She concluded that the relevant questions were whether chrysotile causes mesothelioma and whether the individual had sufficient exposure. She disclosed expert witness work in a 2011–2012 mesothelioma case.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Asbestos exposure among transmission mechanics in automotive repair shops. N. Salazar, M.F. Cely-García, P.N. Breysse, et al. 2015;59(3):292-306. PubMed · Publisher

Abstract

Objectives: Asbestos has been used in a broad variety of industrial products, including clutch discs of the transmission system of vehicles. Studies conducted in high-income countries that have analyzed personal asbestos exposures of transmission mechanics have concluded that these workers are exposed to asbestos concentrations in compliance with the US Occupational Safety and Health Administration (US OSHA) occupational standards. Clutch facings are the friction component of clutch discs. If clutch facings are sold separated from the support, they require manipulation before installation in the vehicle. The manipulation of asbestos containing clutch facings is performed by a group of mechanics known as riveters, and includes drilling, countersinking, riveting, sanding, and occasionally grinding, tasks that can potentially release asbestos fibers, exposing the mechanics. These manipulation activities are not reported in studies conducted in high-income countries. This study analyzes personal asbestos exposures of transmission mechanics that manipulate clutch facings.

Methods: Air sampling campaigns in two transmission repair shops (TRS) were conducted in November 2012 and July 2013 in Bogotá, Colombia. Four workers employed in these TRS were sampled (i.e. three riveters and one supervisor). Personal samples (n = 39), short-term personal samples (n = 49), area samples (n = 52), blank samples (n = 8), and background samples (n = 2) were collected in both TRS during 3-5 consecutive days, following US National Institute for Occupational Safety and Health (US NIOSH) methods 7400 and 7402. Asbestos samples were analyzed by an American Industrial Hygiene Association accredited laboratory.

Results: On at least one of the days sampled, all riveters were exposed to asbestos concentrations that exceeded the US OSHA permissible exposure limit or the Colombian permissible limit value. Additionally, from the forty-seven 30-min short-term personal samples collected, two (4.3%) exceeded the US OSHA excursion limit of 1 f cm(-3).

Conclusions: In this study, we identified that the working conditions and use of asbestos containing transmission products expose transmission mechanics to asbestos concentrations that exceed both the Colombian and OSHA standards. The potential consequences for the health of these workers are of great concern.

© The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Asbestos fibres in the lungs of an American mechanic who drilled, riveted, and ground brake linings: a case report and discussion. M.M. Finkelstein. 2015;59(4):525-7. Case report · Letter PubMed · Publisher

Abstract

In North America and Europe, the use of asbestos in friction products was discontinued before the end of the 20th century. In the developing world, the use of asbestos-containing friction products continues. In 2010, Cely-Garcia and colleagues (Cely-Garcia et al., 2012) sampled three brake repair shops located in Bogota, Colombia. Both asbestos and non-asbestos containing brake linings were sold separately or attached to a shoe. When brake linings are sold separated from the shoe, they must be manipulated to attach them to the shoe before installation. The process starts with the removal of the old brake shoe from the vehicle's brake drum. If the existing brake shoe is to be reused, the old lining needs to be removed and the old shoe must be ground to prepare it for a new lining. Riveting requires drilling holes in the linings and shoes and before installing rivets, the lining must be countersunk. The borders of the lining are bevelled. On some occasions, the entire exposed surface of the lining is ground to make it thinner. Once attached to the shoe, the edges of brake linings may extend beyond the shoe. In this case, it is necessary to cut or grind the edges to match the lining to the shoe before bevelling or grinding. The authors reported that 'the sampling results indicate that the brake mechanics sampled are exposed to extremely high asbestos concentrations (i.e. based on transmission electron microscopy counts), suggesting that this occupational group could be at excess risk of asbestos-related diseases'.

© The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Asbestos Lung Burden in Necroscopic Samples from the General Population of Milan, Italy. M. Casali, M. Carugno, A. Cattaneo, et al. 2015;59(7):909-21. PubMed · Publisher

Abstract

The present study analysed the asbestos lung burden in necroscopic samples from 55 subjects free from asbestos-related diseases, collected between 2009 and 2011 in Milan, Italy. Multiple lung samples were analysed by light microscopy (asbestos bodies, AB) and EDXA-scanning electron microscopy (asbestos fibres and other inorganic fibres). Asbestos fibres were detected in 35 (63.6%) subjects, with a higher frequency for amphiboles than for chrysotile. Commercial (CA) and non-commercial amphiboles (NCA) were found in roughly similar frequencies. The estimated median value was 0.11 million fibres per gram of dry lung tissue (mf g(-1)) for all asbestos, 0.09 mf g(-1) for amphiboles. In 44 (80.0%) subjects no chrysotile fibres were detected. A negative relationship between asbestos mass-weighted fibre count and year of birth (and a corresponding positive increase with age) was observed for amphiboles [-4.15%, 95% confidence interval (CI) = -5.89 to -2.37], talc (-2.12%, 95% CI = -3.94 to -0.28), and Ti-rich fibres (-3.10%, 95% CI = -5.54 to -0.60), but not for chrysotile (-2.84%, 95% CI = -7.69 to 2.27). Residential district, birthplace, and smoking habit did not affect the lung burden of asbestos or inorganic fibres. Females showed higher burden only for amphiboles (0.12 versus 0.03 mf g(-1) in males, P = 0.07) and talc fibres (0.14 versus 0 mf g(-1) in males, P = 0.03). Chrysotile fibres were shorter and thinner than amphibole fibres and NCA fibres were thicker than CA ones. The AB prevalence was 16.4% (nine subjects) with concentrations ranging from 10 to 110 AB g(-1) dry, well below the 1000 AB g(-1) threshold for establishing occupational exposure. No AB were found in subjects younger than 30 years. Our study demonstrated detectable levels of asbestos fibres in a sample taken from the general population. The significant increase with age confirmed that amphibole fibres are the most representative of cumulative exposure.

© The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Characterization of Lone Pine, California, tremolite asbestos and preparation of research material. M. Harper, B. Van Gosen, O.S. Crankshaw, et al. 2015;59(1):91-103. PubMed · Publisher · Free full text

Abstract

Well-characterized amphibole asbestos mineral samples are required for use as analytical standards and in future research projects. Currently, the National Institute for Standards and Technology Standard Reference Material samples of asbestos are listed as 'Discontinued'. The National Institute for Occupational Safety and Health (NIOSH) has a goal under the Asbestos Roadmap of locating and characterizing research materials for future use. Where an initial characterization analysis determines that a collected material is appropriate for use as a research material in terms of composition and asbestiform habit, sufficient amounts of the material will be collected to make it publicly available. An abandoned mine near Lone Pine, California, contains a vein of tremolite asbestos, which was the probable source of a reference material that has been available for the past 17 years from the Health and Safety Laboratory (HSL) in the UK. Newly collected fibrous vein material from this mine was analyzed at Research Triangle Institute (RTI International) with some additional analysis by the US Geological Survey's Denver Microbeam Laboratory. The analysis at RTI International included: (i) polarized light microscopy (PLM) with a determination of principal optical properties; (ii) X-ray diffraction; (iii) transmission electron microscopy, including energy dispersive X-ray spectroscopy and selected-area electron diffraction; and (iv) spindle stage analysis using PLM to determine whether individual fibers and bundles of the samples were polycrystalline or single-crystal cleavage fragments. The overall findings of the study indicated that the material is tremolite asbestos with characteristics substantially similar to the earlier distributed HSL reference material. A larger quantity of material was prepared by sorting, acid-washing and mixing for sub-division into vials of ~10g each. These vials have been transferred from NIOSH to RTI International, from where they can be obtained on request.

Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2014.
Development of a Job-Exposure Matrix (AsbJEM) to Estimate Occupational Exposure to Asbestos in Australia. S.C. van Oyen, S. Peters, H. Alfonso, et al. 2015;59(6):737-48. PubMed · Publisher

Abstract

Introduction: Occupational exposure data on asbestos are limited and poorly integrated in Australia so that estimates of disease risk and attribution of disease causation are usually calculated from data that are not specific for local conditions.

Objective: To develop a job-exposure matrix (AsbJEM) to estimate occupational asbestos exposure levels in Australia, making optimal use of the available exposure data.

Methods: A dossier of all available exposure data in Australia and information on industry practices and controls was provided to an expert panel consisting of three local industrial hygienists with thorough knowledge of local and international work practices. The expert panel estimated asbestos exposures for combinations of occupation, industry, and time period. Intensity and frequency grades were estimated to enable the calculation of annual exposure levels for each occupation-industry combination for each time period. Two indicators of asbestos exposure intensity (mode and peak) were used to account for different patterns of exposure between occupations. Additionally, the probable type of asbestos fibre was determined for each situation.

Results: Asbestos exposures were estimated for 537 combinations of 224 occupations and 60 industries for four time periods (1943-1966; 1967-1986; 1987-2003; ≥2004). Workers in the asbestos manufacturing, shipyard, and insulation industries were estimated to have had the highest average exposures. Up until 1986, 46 occupation-industry combinations were estimated to have had exposures exceeding the current Australian exposure standard of 0.1 f ml(-1). Over 90% of exposed occupations were considered to have had exposure to a mixture of asbestos varieties including crocidolite.

Conclusion: The AsbJEM provides empirically based quantified estimates of asbestos exposure levels for Australian jobs since 1943. This exposure assessment application will contribute to improved understanding and prediction of asbestos-related diseases and attribution of disease causation.

© The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Evaluation of the dark-medium objective lens in counting asbestos fibers by phase-contrast microscopy. E.G. Lee, J.H. Nelson, M.L. Kashon, et al. 2015;59(5):616-28. PubMed · Publisher · Free full text

Abstract

A Japanese round-robin study revealed that analysts who used a dark-medium (DM) objective lens reported higher fiber counts from American Industrial Hygiene Association (AIHA) Proficiency Analytical Testing (PAT) chrysotile samples than those using a standard objective lens, but the cause of this difference was not investigated at that time. The purpose of this study is to determine any major source of this difference by performing two sets of round-robin studies. For the first round-robin study, 15 AIHA PAT samples (five each of chrysotile and amosite generated by water-suspended method, and five chrysotile generated by aerosolization method) were prepared with relocatable cover slips and examined by nine laboratories. A second round-robin study was then performed with six chrysotile field sample slides by six out of nine laboratories who participated in the first round-robin study. In addition, two phase-shift test slides to check analysts' visibility and an eight-form diatom test plate to compare resolution between the two objectives were examined. For the AIHA PAT chrysotile reference slides, use of the DM objective resulted in consistently higher fiber counts (1.45 times for all data) than the standard objective (P-value < 0.05), regardless of the filter generation (water-suspension or aerosol) method. For the AIHA PAT amosite reference and chrysotile field sample slides, the fiber counts between the two objectives were not significantly different. No statistically significant differences were observed in the visibility of blocks of the test slides between the two objectives. Also, the DM and standard objectives showed no pattern of differences in viewing the fine lines and/or dots of each species images on the eight-form diatom test plate. Among various potential factors that might affect the analysts' performance of fiber counts, this study supports the greater contrast caused by the different phase plate absorptions as the main cause of high counts for the AIHA PAT chrysotile slides using the DM objective. The comparison of fiber count ratios (DM/standard) between the AIHA PAT chrysotile samples and chrysotile field samples indicates that there is a fraction of fibers in the PAT samples approaching the theoretical limit of visibility of the phase-contrast microscope with 3-degree phase-shift. These fibers become more clearly visible through the greater contrast from the phase plate absorption of the DM objective. However, as such fibers are not present in field samples, no difference in counts between the two objectives was observed in this study. The DM objective, therefore, could be allowed for routine fiber counting as it will maintain continuity with risk assessments based on earlier phase-contrast microscopy fiber counts from field samples. Published standard methods would need to be modified to allow a higher aperture specification for the objective.

Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2015.

In plain English

This laboratory methods study looked at how the choice of microscope lens affects counts of asbestos fibers under phase-contrast microscopy, the standard method for measuring airborne asbestos. It did not study health effects. Nine laboratories counted fibers on 15 proficiency-testing reference slides (ten chrysotile, five amosite). All of them used the same circulated Nikon microscope, counting once with a standard objective lens (DLL, numerical aperture 0.75) and once with a 'dark-medium' (DM) lens (numerical aperture 0.95). Six of the labs then counted six chrysotile slides made from older workplace air samples whose site is unknown. With the DM lens, counts on the chrysotile reference slides were significantly higher; the authors give 1.45 times for all data. Counts did not differ significantly between the two lenses for the amosite reference slides or the chrysotile field slides. Test slides and a diatom test plate showed no consistent differences between the lenses in visibility or resolution. The authors concluded that the greater contrast of the DM lens was the main cause of the higher counts. They concluded the DM lens could be allowed for routine counting, although published standard methods would need to be changed. They noted that the field results came from only six slides from a single site.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.
Malignant mesotheliomas in textile rag sorters. E. Chellini, G. Martino, A. Grillo, et al. 2015;59(5):547-53. PubMed · Publisher

Abstract

Objectives: To analyse the asbestos exposure characteristics and mesothelioma trend in textile workers operating in the larger Tuscan textile industrial province of Prato between 1988 and 2012.

Methods: All cases of textile workers recorded by the Tuscan mesothelioma register are considered. The demographic and clinical characteristics and asbestos exposure of cases working in the province of Prato are examined. Crude incidence rates between 1988 and 2012 and their 95% confidence intervals (CI) are calculated in rag sorters and other textile workers. The trends of standardized rates are also evaluated, as well as the sources of occupational asbestos exposure from occupational histories of cases affected by other asbestos-related diseases in rag sorters.

Results: One hundred and seventy-two malignant mesotheliomas (MMs) have been diagnosed in textile workers in Tuscany. Among these, 46.5% were residents in the province of Prato at the time of diagnosis, half of whom working as rag sorters. All rag sorters with MM are classified as occupationally asbestos exposed, while 71.7% are other textile workers exposed to asbestos. The estimated crude incidence rate in rag sorters in Prato ranges from 74.1×100000 (95% CI: 52.5-101.8) to 166.8×100000 (95% CI: 118.1-229.0). The standardized rates in Prato rag sorters appeared higher throughout the 1990s while in other Prato textile workers the rates increased later on, at the very end of the 1990s. Another 40 cases of asbestos-related diseases in rag sorters were also collected.

Conclusions: A very high incidence of MMs was observed in textile workers in Prato, especially among rag sorters. This result, together with the high number of other asbestos-related diseases in rag sorters, strongly supports the hypothesis of diffuse asbestos exposure in rag sorting, in the absence of any other relevant aetiological factor for malignant mesothelioma.

© The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Mesothelioma in a wine cellar man: detailed description of working procedures and past asbestos exposure estimation. A. Nemo, S. Silvestri. 2014;58(9):1168-74. Case report PubMed · Publisher

Abstract

A pleural mesothelioma arose in an employee of a wine farm whose work history shows an unusual occupational exposure to asbestos. The information, gathered directly from the case and from a work colleague, clarifies some aspects of the use of asbestos in the process of winemaking which has not been previously reported in such details. The man had worked as a winemaker from 1960 to 1988 in a farm, which in those years produced around 2500 hectoliters of wine per year, mostly white. The wine was filtered to remove impurities; the filter was created by dispersing in the wine asbestos fibers followed by diatomite while the wine was circulating several times and clogging a prefilter made of a dense stainless steel net. Chrysotile asbestos was the sole asbestos mineralogical variety used in these filters and exposure could occur during the phase of mixing dry fibers in the wine and during the filter replacement. A daily and annual time weighted average level of exposure and cumulative dose have been estimated in the absence of airborne asbestos fiber monitoring performed in that workplace. Since 1993, the Italian National Mesothelioma Register, an epidemiological surveillance system, has recorded eight cases with at least one work period spent as winemaker. Four of them never used asbestos filters and presented exposures during other work periods, the other four used asbestos filters but had also other exposures in other industrial divisions. For the information hitherto available, this is the first mesothelioma case with exclusive exposure in the job of winemaking.

© The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
Trends in asbestos and non-asbestos fibre concentrations in the lung tissues of Japanese patients with mesothelioma. K. Sakai, N. Hisanaga, E. Shibata, et al. 2014;58(1):103-20. PubMed · Publisher

Abstract

Objectives: We aimed to elucidate changes in asbestos and non-asbestos fibre concentrations in the lung tissues of Japanese patients with mesothelioma over time.

Methods: Lung tissues were obtained from 46 patients with mesothelioma who died or underwent surgery between 1971 and 2005. All of the patients had a history of occupational asbestos exposure. We classified patients into four groups according to the period during which their lung tissue was obtained. Asbestos and non-asbestos fibre concentrations were determined by transmission electron microscopy with energy-dispersive X-ray analysis using a low-temperature ashing procedure.

Results: From the 1970s to the 2000s, we observed a decrease in the geometric mean of total asbestos concentration (67.4-1.05 million fibres per gram dry lung), chrysotile concentration (25.0-0.66 million fibres per gram dry lung), amphibole asbestos concentration (21.3-0.76 million fibres per gram dry lung), and non-asbestos fibre concentration (326-19.3 million fibres per gram dry lung). The mean duration of asbestos exposure decreased from 33.7 to 17.6 years, and the mean duration since the last exposure increased from 0.3 to 21.5 years. The percentage of longer fibres to total fibres tended to increase over time, whereas the mean fibre length did not differ significantly.

Conclusions: The present study suggested that asbestos and non-asbestos fibre concentrations in the lung tissues of Japanese patients with mesothelioma who have occupational histories of asbestos exposure may have decreased from the 1970s to the 2000s.
Comprehensive assessment of exposures to elongate mineral particles in the taconite mining industry. J. Hwang, G. Ramachandran, P.C. Raynor, et al. 2013;57(8):966-78. PubMed · Publisher

Abstract

Since the 1970s, concerns have been raised about elevated rates of mesothelioma in the vicinity of the taconite mines in the Mesabi Iron Range. However, insufficient quantitative exposure data have hampered investigations of the relationship between cumulative exposures to elongate mineral particles (EMP) in taconite dust and adverse health effects. Specifically, no research on exposure to taconite dust, which includes EMP, has been conducted since 1990. This article describes a comprehensive assessment of present-day exposures to total and amphibole EMP in the taconite mining industry. Similar exposure groups (SEGs) were established to assess present-day exposure levels and buttress the sparse historical data. Personal samples were collected to assess the present-day levels of worker exposures to EMP at six mines in the Mesabi Iron Range. The samples were analyzed using National Institute for Occupational Safety and Health (NIOSH) methods 7400 and 7402. For many SEGs in several mines, the exposure levels of total EMP were higher than the NIOSH Recommended Exposure Limit (REL). However, the total EMP classification includes not only the asbestiform EMP and their non-asbestiform mineral analogs but also other minerals because the NIOSH 7400 cannot differentiate between these. The concentrations of amphibole EMP were well controlled across all mines and were much lower than the concentrations of total EMP, indicating that amphibole EMP are not major components of taconite EMP. The levels are also well below the NIOSH REL of 0.1 EMP cc(-1). Two different approaches were used to evaluate the variability of exposure between SEGs, between workers, and within workers. The related constructs of contrast and homogeneity were calculated to characterize the SEGs. Contrast, which is a ratio of between-SEG variability to the sum of between-SEG and between-worker variability, provides an overall measure of whether there are distinctions between the SEGs. Homogeneity, which is the ratio of the within-worker variance component to the sum of the between-worker and within-worker variance components, provides an overall measure of how similar exposures are for workers within an SEG. Using these constructs, it was determined that the SEGs are formed well enough when grouped by mine for both total and amphibole EMP to be used for epidemiological analysis.
JEMs and incompatible occupational coding systems: effect of manual and automatic recoding of job codes on exposure assignment. T. Koeman, N.S. Offermans, Y. Christopher-de Vries, et al. 2013;57(1):107-14. PubMed · Publisher

Abstract

Background: In epidemiological studies, occupational exposure estimates are often assigned through linkage of job histories to job-exposure matrices (JEMs). However, available JEMs may have a coding system incompatible with the coding system used to code the job histories, necessitating a translation of the originally assigned job codes. Since manual recoding is usually not feasible in large studies, this is often done by use of automated crosswalks translating job codes from one system to another. We set out to investigate whether automatically translating job codes led to different exposure estimates compared with those resulting from manual recoding using the original job descriptions.

Methods: One hundred job histories were randomly drawn from the Netherlands Cohort Study on diet and cancer (NLCS), using a sampling strategy designed to oversample potentially exposed jobs. This resulted in 220 job codes that were automatically translated from the original Dutch coding system to the International Standard Classification of Occupations (ISCO)-68 and ISCO-88 as well as manually recoded from the job descriptions in the original questionnaire by two coders. Exposure to several agents (i.e. chromium, asbestos, silica, pesticides, aromatic solvents, and extremely low-frequency magnetic fields) was assigned by JEMs based on job codes resulting from automatic and manual recodings.

Results: The agreement between occupational exposure estimates based on the crosswalk versus those based on manual recoding reached a Cohen's Kappa (κ) of 0.66 or higher and were similar to the agreements between the two coders.

Conclusions: Results of this study indicate that using automated crosswalks to recode job codes from one occupational classification system to another results only in a limited loss in agreement in assigned occupational exposure estimates compared with direct manual recoding. Therefore, in this case, crosswalks provide an efficient alternative to the costly and time-consuming direct manual recoding from job history descriptions from questionnaires.
Quality of evidence must guide risk assessment of asbestos, by Lenters, V; Burdorf, A; Vermeulen, R; Stayner, L; Heederik, D. J.T. Hodgson. 2013;57(5):670-4. Letter · Comment PubMed · Publisher
Quality of evidence must guide risk assessment of asbestos, by Lenters, V; Burdorf, A; Vermeulen, R; Stayner, L; Heederik, D. D.W. Berman, B.W. Case. 2013;57(5):667-9. Letter · Comment PubMed · Publisher
Reply: response to the letter by Drs Berman and Case. D. Heederik, V. Lenters, R. Vermeulen. 2013;57(5):675-7. Letter · Comment PubMed · Publisher
Trends of occupational exposure to chemical agents in Finland in 1950-2020. T. Kauppinen, S. Uuksulainen, A. Saalo, et al. 2013;57(5):593-609. PubMed · Publisher

Abstract

Introduction: The aim of this study was to quantitatively estimate the long-term trends of occupational exposure to chemical agents in Finland for surveillance, prevention, and risk assessment purposes.

Methods: We studied trends by utilizing the Finnish job-exposure matrix (FINJEM), which includes occupation-specific estimates of the prevalence P (percent of employed) and average level L (agent-specific units) of inhalation exposure to chemical agents at different time periods. We used FINJEM data to calculate national estimates of the numbers of exposed workers (N exp), and the prevalence of and level of exposure to 41 chemical agents in 1950, 1970, 1990, and 2008. We also estimated the prevalence of employees exposed to levels exceeding 50% of the Finnish occupational exposure limit (OEL) (P high) and national occupational inhalation exposure (NOIE = N exp × L). Future exposures in 2020 were estimated according to the predicted change of the occupational structure of the labor force and the observed agent-specific exposure trends in 1990-2008. We estimated dermal exposure indirectly from the statistics of occupational skin diseases in 1975-2009.

Results: Inhalation exposure to most chemical agents had decreased. Using 1990 as the reference (100), the median values of P for 1950, 1970, 1990, 2008, and 2020 were 91, 149, 100, 58, and 41, respectively. The corresponding values were 218, 224, 100, 30, and 14 for P high, 151, 121, 100, 78, and 66 for L, and 119, 176, 100, 38, and 20 for NOIE. The trends varied considerably according to the agent. Exposure of, for example, asbestos, benzene, and benzo(a)pyrene substantially decreased. The annual incidence of occupational skin diseases due to chemical factors decreased from 6.9 per 10 000 employed in 1975-1979 to 4.6 per 10 000 in 2000-2009, suggesting a decrease in dermal exposure.

Conclusions: Inhalation exposure to most chemical agents has decreased in Finland since 1970. High exposures and the average level of exposure started to decrease already in the 1950s. The declining incidence of occupational skin diseases suggests that dermal exposure has also diminished. However, high exposures still exist and cause a substantial amount of occupational diseases and symptoms. Chemical exposures and the related disease burden are expected to continue decreasing in the future. These results cannot be generalized to other countries, particularly if the development phase of technology and the occupational structure of the labor force differ significantly from those in Finland.
Airborne concentrations of chrysotile asbestos in serpentine quarries and stone processing facilities in Valmalenco, Italy. A. Cattaneo, A. Somigliana, M. Gemmi, et al. 2012;56(6):671-83. PubMed · Publisher

Abstract

Asbestos may be naturally present in rocks and soils. In some cases, there is the possibility of releasing asbestos fibres into the atmosphere from the rock or soil, subsequently exposing workers and the general population, which can lead to an increased risk of developing asbestos-related diseases. In the present study, air contaminated with asbestos fibres released from serpentinites was investigated in occupational settings (quarries and processing factories) and in the environment close to working facilities and at urban sites. The only naturally occurrence of asbestos found in Valmalenco area was chrysotile; amphibole fibres were never detected. An experimental cut-off diameter of 0.25 μm was established for distinguishing between Valmalenco chrysotile and antigorite single fibres using selected area electron diffraction analyses. Air contamination from chrysotile fibres in the examined occupational settings was site-dependent as the degree of asbestos contamination of Valmalenco serpentinites is highly variable from place to place. Block cutting of massive serpentinites with multiple blades or discs and drilling at the quarry sites that had the highest levels of asbestos contamination generated the highest exposures to (i.e. over the occupational exposure limits) asbestos. Conversely, working activities on foliated serpentinites produced airborne chrysotile concentrations comparable with ambient levels. Environmental chrysotile concentrations were always below the Italian limit for life environments (0.002 f ml(-1)), except for one sample collected at a quarry property boundary. The present exposure assessment study should encourage the development of an effective and concordant policy for proper use of asbestos-bearing rocks and soils as well as for the protection of public health.
An inter-laboratory study to determine the effectiveness of procedures for discriminating amphibole asbestos fibers from amphibole cleavage fragments in fiber counting by phase-contrast microscopy. M. Harper, E.G. Lee, J.E. Slaven, et al. 2012;56(6):645-59. PubMed · Publisher

Abstract

The US Occupational Safety and Health Administration (OSHA) and Mine Safety and Health Administration do not regulate cleavage fragments of amphibole and serpentine minerals as asbestos, even when particles meet the dimensional criteria for counting under standard phase-contrast microscopy methods. The OSHA ID-160 method cautions that discriminatory counting is difficult and should not be attempted unless necessary and no procedure is provided for differentiation. A standard published by the American Society for Testing and Materials (ASTM International D7200-06) includes an attempt to codify a procedure but recognizes that the procedure should be validated in an inter-laboratory study. The US National Institute for Occupational Safety and Health has carried out such a study with multiple laboratories using slides made from riebeckite and crocidolite, grunerite and amosite, tremolite and tremolite asbestos, and actinolite and actinolite asbestos using two different measurement aids (graticules). The asbestos fibers had dimensions consistent with those reported for air samples from actual amphibole asbestos operations, and the cleavage fragments were also dimensionally consistent with those found in non-asbestos mining and milling operations. The procedure for discriminating asbestos fibers from other mineral particles in the ASTM Standard calls for the recognition of characteristics supposedly common to asbestos. For the asbestos fibers created in this study, these characteristics were found not to be common and generally a function of length. More importantly, different laboratories did not recognize these features consistently. Laboratories were much more consistent in measuring dimensions, but excessive overlap in the lengths of asbestos fibers and cleavage fragments rendered length a poor criterion for discrimination. The ASTM discrimination procedure as written could not be supported on the basis of this study. Width was a much more consistent parameter for distinguishing the asbestos and non-asbestos fibers in this study and inclusion of aspect ratio, while considered important by some researchers, did not refine the discrimination further. The ability of the majority of microscopists in this study to discriminate fibers and cleavage fragments through measurement of particle widths was determined and found to be within limits of uncertainty typical for air sampling measurements. A width criterion might be a very simple and useful aid where discrimination between asbestos and non-asbestos fibers in fiber counting by phase-contrast microscopy is required for further investigation. Recognition of asbestos features can also be retained as excessive recognition by some laboratories will lead to a conservative decision for additional investigation.
Asbestos exposure during uncontrolled removal of sprayed-on asbestos. P. Dumortier, P. De Vuyst. 2012;56(1):49-54. Case report PubMed · Publisher

Abstract

Asbestos-containing materials in place in buildings, especially sprayed-on asbestos, are still an important health threat. Clearance of these materials has to be operated by specifically trained workers wearing specific individual protection suits after containment of the contaminated area. Good work practices are, however, not always applied. We report the case of two workers hired for ∼1 week to remove sprayed-on amosite asbestos during the remodeling of a former industrial hall. Regulatory protective equipments were not used. A legal action was initiated after disclosure of the working conditions. Medical examinations were performed 18 and 22 months after exposure. Workers denied any other asbestos exposure. Lung function tests and chest computed tomography scans were normal. Very high levels of asbestos fibers and bodies were discovered on mineralogical analysis of bronchoalveolar lavage fluid (BALF) by phase contrast light microscopy and analytical electron microscopy. All fibers were amosite. An extrapolation considering duration of exposure, breathing pattern, and BALF fiber content suggests that the workers were exposed to airborne fiber concentrations in the range from several tens to about a hundred World Health Organization fibers per milliliter air. In conclusion, exposures to historical airborne fiber levels prevailing half a century ago may still occur today when the work regulations are not applied. In these conditions, even very short exposures may result in considerable lung fiber retention in case of amphibole exposure with the subsequent risk for developing asbestos-related diseases. Fiber analysis in BALF is useful to clarify such exposures.
Asbestos fibre burden in the lungs of patients with mesothelioma who lived near asbestos-cement factories. P.G. Barbieri, D. Mirabelli, A. Somigliana, et al. 2012;56(6):660-70. PubMed · Publisher

Abstract

Background: Epidemics of malignant mesothelioma are occurring among inhabitants of Casale Monferrato and Bari never employed in the local asbestos-cement (AC) factories. The mesothelioma risk increased with proximity of residence to both plants.

Objectives: To provide information on the intensity of environmental asbestos exposure, in the general population living around these factories, through the evaluation of the lung fibre burden in mesothelioma patients.

Methods: We analysed by a scanning electron microscope equipped with X-ray microanalysis wet (formalin-fixed) lung tissue samples from eight mesothelioma patients who lived in Casale Monferrato or Bari and underwent surgery. Their occupational and residential history was obtained during face-to-face interviews. Semi-quantitative and quantitative indices of cumulative environmental exposure to asbestos were computed, based on residential distance from the AC plants and duration of stay.

Results: The lung fibre burden ranged from 110 000 to 4 300 000 fibres per gram of dry lung (f/g) and was >1 000 000 f/g in three subjects. In four cases, only amphibole fibres were detected. Environmental exposures had ceased at least 10 years before samples were taken. No patient had other definite or probable asbestos exposures. A linear relationship was observed between the lung fibre burden and all three indices of environmental cumulative exposure to asbestos.

Conclusions: Environmental exposure to a mixture of asbestos fibres may lead to a high lung fibre burden of amphiboles years after exposure cessation. The epidemiological evidence of an increased mesothelioma risk for the general population of Casale Monferrato and Bari, associated with asbestos contamination of the living environment, is corroborated.
Asbestos-related diseases in automobile mechanics. J. Ameille, N. Rosenberg, M. Matrat, et al. 2012;56(1):55-60. PubMed · Publisher · Free full text

Abstract

Purpose: Automobile mechanics have been exposed to asbestos in the past, mainly due to the presence of chrysotile asbestos in brakes and clutches. Despite the large number of automobile mechanics, little is known about the non-malignant respiratory diseases observed in this population. The aim of this retrospective multicenter study was to analyse the frequency of pleural and parenchymal abnormalities on high-resolution computed tomography (HRCT) in a population of automobile mechanics.

Methods: The study population consisted of 103 automobile mechanics with no other source of occupational exposure to asbestos, referred to three occupational health departments in the Paris area for systematic screening of asbestos-related diseases. All subjects were examined by HRCT and all images were reviewed separately by two independent readers; who in the case of disagreement discussed until they reached agreement. Multiple logistic regression models were constructed to investigate factors associated with pleural plaques.

Results: Pleural plaques were observed in five cases (4.9%) and interstitial abnormalities consistent with asbestosis were observed in one case. After adjustment for age, smoking status, and a history of non-asbestos-related respiratory diseases, multiple logistic regression models showed a significant association between the duration of exposure to asbestos and pleural plaques.

Conclusions: The asbestos exposure experienced by automobile mechanics may lead to pleural plaques. The low prevalence of non-malignant asbestos-related diseases, using a very sensitive diagnostic tool, is in favor of a low cumulative exposure to asbestos in this population of workers.
Development of an exposure measurement database on five lung carcinogens (ExpoSYN) for quantitative retrospective occupational exposure assessment. S. Peters, R. Vermeulen, A. Olsson, et al. 2012;56(1):70-9. PubMed · Publisher

Abstract

Background: SYNERGY is a large pooled analysis of case-control studies on the joint effects of occupational carcinogens and smoking in the development of lung cancer. A quantitative job-exposure matrix (JEM) will be developed to assign exposures to five major lung carcinogens [asbestos, chromium, nickel, polycyclic aromatic hydrocarbons (PAH), and respirable crystalline silica (RCS)]. We assembled an exposure database, called ExpoSYN, to enable such a quantitative exposure assessment.

Methods: Existing exposure databases were identified and European and Canadian research institutes were approached to identify pertinent exposure measurement data. Results of individual air measurements were entered anonymized according to a standardized protocol.

Results: The ExpoSYN database currently includes 356 551 measurements from 19 countries. In total, 140 666 personal and 215 885 stationary data points were available. Measurements were distributed over the five agents as follows: RCS (42%), asbestos (20%), chromium (16%), nickel (15%), and PAH (7%). The measurement data cover the time period from 1951 to present. However, only a small portion of measurements (1.4%) were performed prior to 1975. The major contributing countries for personal measurements were Germany (32%), UK (22%), France (14%), and Norway and Canada (both 11%).

Conclusions: ExpoSYN is a unique occupational exposure database with measurements from 18 European countries and Canada covering a time period of >50 years. This database will be used to develop a country-, job-, and time period-specific quantitative JEM. This JEM will enable data-driven quantitative exposure assessment in a multinational pooled analysis of community-based lung cancer case-control studies.
More on the dynamics of dust generation: the effects of mixing and sanding chrysotile, calcium carbonate, and other components on the characteristics of joint-compound dusts. D.W. Berman, G.P. Brorby, P.J. Sheehan, et al. 2012;56(7):852-67. PubMed · Publisher

Abstract

An ongoing research effort designed to reconstruct the character of historical exposures associated with use of chrysotile-containing joint compounds naturally raised questions concerning how the character (e.g. particle size distributions) of dusts generated from use of recreated materials compares to dusts from similar materials manufactured historically. This also provided an opportunity to further explore the relative degree that the characteristics of dusts generated from a bulk material are mediated by the properties of the bulk material versus the mechanical processes applied to the bulk material by which the dust is generated. In the current study, the characteristics of dusts generated from a recreated ready mix and recreated dry mix were compared to each other, to dusts from a historical dry mix, and to dusts from the commercial chrysotile fiber (JM 7RF3) used in the recreated materials. The effect of sanding on the character of dusts generated from these materials was also explored. Dusts from the dry materials studied were generated and captured for analysis in a dust generator-elutriator. The recreated and historical joint compounds were also prepared, applied to drywall, and sanded inside sealed bags so that the particles produced from sanding could be introduced into the elutriator and captured for analysis. Comparisons of fiber size distributions in dusts from these materials suggest that dust from commercial fiber is different from dusts generated from the joint compounds, which are mixtures, and the differences persist whether the materials are sanded or not. Differences were also observed between sanded recreated ready mix and either the recreated dry mix or a historical dry mix, again whether sanded or not. In all cases, however, such differences disappeared when variances obtained from surrogate data were used to better represent the 'irreducible variation' of these materials. Even using the smaller study-specific variances, no differences were observed between the recreated dry mix and the historical dry mix, indicating that chrysotile-containing joint compounds can be recreated using historical formulations such that the characteristics of the modern material reasonably mimic those of a corresponding historical material. Similarly, no significant differences were observed between dusts from sanded and unsanded versions of similar materials, suggesting (as in previous studies) that the characteristics of asbestos-containing dusts are mediated primarily by the properties of the bulk material from which they are derived.
Overreliance on a single study: there is no real evidence that applying quality criteria to exposure in asbestos epidemiology affects the estimated risk. D.W. Berman, B.W. Case. 2012;56(8):869-78. PubMed · Publisher

Abstract

A critical need exists for reliable risk management policies and practices that can effectively mitigate asbestos-related health threats, and such policies and practices need to be based on sound science that adequately distinguishes hazardous situations from those that are not. Toward that end, the disparate means by which study quality has been addressed in recent meta-analyses used to establish potency factors (K ( L ) and K ( M ) values) for asbestos cancer risks were compared by conducting additional sensitivity analyses. Results suggest that, other than placing undue emphasis on the influence of the K ( L ) and K ( M ) values reported from a single study, there appears to be little to no evidence of a systematic effect of study quality on K ( L ) or K ( M ) values; none of the findings warrant excluding studies from current or future meta-analyses. Thus, we argue that it is better to include as much of the available data as possible in these analyses while formally addressing uncertainty as part of the analysis itself, rather than sequentially excluding studies based on one type of limitation or another. Throwing out data without clearly proving some type of bias is never a good idea because it will limit both the power to test various hypotheses and the confidence that can be placed in any findings that are derived from the resulting, truncated data set. We also believe that it is better to identify the factors that contribute to variation between studies included in a meta-analysis and, by adjusting for such factors as part of a model, showing that the disparate values from individual studies can be reconciled. If such factors are biologically reasonable (based on other evidence) and, if such a model can be shown to fit the data from all studies in the meta-analysis, the model is likely to be predictive of the parameters being evaluated and can then be applied to new (unstudied) environments.
Personal exposures to asbestos fibers during brake maintenance of passenger vehicles. M.F. Cely-García, M. Sánchez, P.N. Breysse, et al. 2012;56(9):985-99. PubMed · Publisher

Abstract

Introduction: Brake linings and brake pads are among the asbestos-containing products that are readily available in Colombia. When sold separated from their support, brake linings require extensive manipulation involving several steps that include drilling, countersinking, riveting, bonding, cutting, beveling, and grinding. Without this manipulation, brake linings cannot be installed in a vehicle. The manipulation process may release asbestos fibers, which may expose brake mechanics to the fibers.

Methods: Three brake repair shops located in Bogotá (Colombia) were sampled for 3 or 4 consecutive days using US National Institute for Occupational Safety and Health (NIOSH) methods 7400 and 7402. Standard procedures for quality control were followed during the sampling process, and asbestos samples were analyzed by an American Industrial Hygiene Association accredited laboratory. Personal samples were collected to assess full-shift and short-term exposures. Area samples were also collected close to the brake-lining manipulation equipment and within office facilities. Activities were documented during the sampling process.

Results: Using Phase Contrast Microscopy Equivalent counts to estimate air asbestos concentrations, all personal samples [i.e. 8-h time-weighted averages (TWAs) and 30-min personal samples] were in compliance with the US Occupational Safety and Health Administration standards. Personal asbestos concentrations based on transmission electron microscopy counts were extremely high, ranging from 0.006 to 3.493 f cm(-3) for 8-h TWA and from 0.015 to 8.835 f cm(-3) for 30-min samples. All asbestos fibers detected were chrysotile. Cleaning facilities and grinding linings resulted in the highest asbestos exposures based on transmission electron microscopy counts. There were also some samples that did not comply with the NIOSH's recommended exposure limits.

Conclusion: The results indicate that the brake mechanics sampled are exposed to extremely high asbestos concentrations (i.e. based on transmission electron microscopy counts), suggesting that this occupational group could be at excess risk of asbestos-related diseases.
Pulmonary carcinoid tumors and asbestos exposure. B. Clin, P. Andujar, I. Abd Al Samad, et al. 2012;56(7):789-95. PubMed · Publisher · Free full text

Abstract

Objectives: The hypothesis that asbestos exposure may have more specific associations with particular histological types of lung cancer remains controversial. The aim of this study was to analyze the relationships between asbestos exposure and pulmonary carcinoid tumors.

Methods: A retrospective case-control study was conducted in 28 cases undergoing surgery for pulmonary carcinoid tumors and aged >40 years and in 56 controls with lung cancer of a different histological type, matched for gender and age, from 1994 to 1999, recruited in two hospitals in the region of Paris. Asbestos exposure was assessed via expertise of a standardized occupational questionnaire and mineralogical analysis of lung tissue, with quantification of asbestos bodies (AB).

Results: Definite asbestos exposure was identified in 25% of cases and 14% of controls (ns). Cumulative asbestos exposure was significantly higher in cases than in controls (P < 0.05), and results of the quantification of AB tended to be higher in cases than in controls (24 and 9% had >1000 AB per gram dry lung tissue, respectively, P = 0.09). Mean cumulative smoking was lower in cases than in controls (P < 0.05).

Conclusions: This study argues in favor of a relationship between asbestos exposure and certain pulmonary carcinoid tumors.
Quality of evidence must guide risk assessment of asbestos. V. Lenters, A. Burdorf, R. Vermeulen, et al. 2012;56(8):879-87. PubMed · Publisher

Abstract

In 2011, we reported on the sensitivity of lung cancer potency estimates for asbestos to the quality of the exposure assessment component of underlying evidence. Both this meta-analysis and a separate reassessment of standards published by the Health Council of the Netherlands (Gezondheidsraad) have been commented on by Berman and Case. A criticism is that we used a truncated data set. We incrementally excluded poorer-quality studies to evaluate trends in meta-analyzed lung cancer potency estimates (meta-K (L) values). This was one of three analysis approaches we presented. The other two used the full set of studies: a meta-analysis stratified by covariates and dichotomized by poorer and better exposure assessment aspects; and a meta-regression modeling both asbestos fiber type and these covariates. They also state that our results are not robust to removal of one study. We disagree with this claim and present additional sensitivity analyses underpinning our earlier conclusion that inclusion of studies with higher-quality asbestos-exposure assessment yield higher meta-estimates of the lung cancer risk per unit of exposure. We reiterate that potency differences for predominantly chrysotile- versus amphibole-asbestos-exposed cohorts are difficult to ascertain when meta-analyses are restricted to studies with fewer exposure assessment limitations. We strongly argue that the existence of any uncertainty related to potency issues should not hamper the development of appropriate evidence-based guidelines and stringent policies in order to protect the public from hazardous environmental and occupational exposures.
Applying quality criteria to exposure in asbestos epidemiology increases the estimated risk. A. Burdorf, D. Heederik. 2011;55(6):565-8. PubMed · Publisher

Abstract

Mesothelioma deaths due to environmental exposure to asbestos in The Netherlands led to parliamentary concern that exposure guidelines were not strict enough. The Health Council of the Netherlands was asked for advice. Its report has recently been published. The question of quality of the exposure estimates was studied more systematically than in previous asbestos meta-analyses. Five criteria of quality of exposure information were applied, and cohort studies that failed to meet these were excluded. For lung cancer, this decreased the number of cohorts included from 19 to 3 and increased the risk estimate 3- to 6-fold, with the requirements for good historical data on exposure and job history having the largest effects. It also suggested that the apparent differences in lung cancer potency between amphiboles and chrysotile may be produced by lower quality studies. A similar pattern was seen for mesothelioma. As a result, the Health Council has proposed that the occupational exposure limit be reduced from 10 000 fibres m(-3) (all types) to 250 f m(-3) (amphiboles), 1300 f m(-3) (mixed fibres), and 2000 f m(-3) (chrysotile). The process illustrates the importance of evaluating quality of exposure in epidemiology since poor quality of exposure data will lead to underestimated risk.
Chamber for testing asbestos-containing products: validation and testing of a re-created chrysotile-containing joint compound. P.J. Sheehan, G.P. Brorby, D.W. Berman, et al. 2011;55(7):797-809. PubMed · Publisher

Abstract

Joint compound products containing chrysotile asbestos were commonly used for building construction from the late 1940s through the mid-1970s. Few relevant data exist to support reconstructing historical worker exposures to fibers generated by working with this material. Therefore, we re-created 1960s-era chrysotile-containing joint compound (JCC) and compared its characteristics to a current-day asbestos-free joint compound (JCN). Validation studies showed that a bench-scale chamber with controlled flow dynamics, designed to quantify particulate emissions from joint compound products, provided precise and reliable measurements of generated airborne dust mass, chrysotile fiber concentrations, and corresponding activity-specific emission rates. Subsequent chamber studies characterized fibers counted by phase contrast microscopy (PCM) per mass of respirable dusts and total suspended particulate dusts (total dusts), generated during JCC sanding or sweeping, as well as corresponding dust emission rates for JCC and JCN, and the ratio of total to respirable dust mass for JCN. From these data we estimated factors, F(CH-rd) and F(CH-td) (in units of f cm(-3) per mg m(-3)), by which respirable JCN dust mass concentrations collected during construction use can be converted to corresponding airborne PCM fiber concentrations generated by sanding or sweeping JCC. For sanding, median values (95% confidence limits) of F(CH-rd) and F(CH-td) were estimated to be 0.044 (0.039-0.050) and 0.212 (0.115-0.390) f cm(-3) per mg m(-3), respectively. The F(CH-td) to F(CH-rd) ratio indicates that approximately five times as many airborne PCM fibers are anticipated per unit air volume sampled when JCC dust is collected on cassettes (as done historically), than when respirable JCC dust is collected on cyclones. As the sizes of individual fibers collected appear to be primarily respirable, this difference may be a sampling artifact and suggests caution in interpreting historical fiber concentration measures made using cassettes during work with JCC-like materials. F(CH-rd) can be used with published and newly generated field measurements of respirable dust mass concentrations associated with the use of JCN or equivalent JCN materials to better characterize historical worker exposures to PCM fibers from use of JCC or equivalent JCCs. The experimental process described also can be used to develop conversion factors for other combinations of modern-day asbestos-free and historical chrysotile-containing products.
Comparison of mounting methods for the evaluation of fibers by phase contrast microscopy. E.G. Lee, T.W. Pang, J. Nelson, et al. 2011;55(6):644-57. PubMed · Publisher

Abstract

The objectives of this study were to evaluate mounting methods for fiber examination of air sample filters by phase contrast microscopy (PCM) and to evaluate differences in fiber counts that might be due to fiber movement. Acetone/triacetin (AT) with various amounts of triacetin and acetone/Euparal (AE) where the mounting medium was placed between the cleared filter wedge and the coverslip were tested as a function of time. Field sample slides collected from a taconite iron-ore processing mill, a tremolitic talc-ore processing mill, and from around a crusher in a meta-basalt stone quarry were prepared with relocatable coverslips to revisit the same field areas on the slides. For each slide, three or four field areas were randomly selected and pictures were taken every 2 weeks to determine any sign of fiber movement over time. For 11 AT slides (named as AT-3.5) prepared with 3.5 μl of the mounting medium according to the NIOSH 7400 method, no fiber movements were detected over 59 weeks. On the other hand, AT slides prepared with larger quantities (10, 15, and 20 μl) of the mounting medium (named as AT-10) and AE slides prepared with ∼10 μl mounting medium showed fiber movement from the eighth day at the earliest. Fiber movement began earlier for the slides mounted with excess triacetin than for those mounted with Euparal. The sample slide storage method, either vertically or horizontally, did not seem to accelerate fiber movement. Additionally, two other modified methods, dimethylformamide solution/Euparal (mDE) and dimethylformamide solution/triacetin (mDT), were also prepared where the mounting medium was placed between the cleared filter wedge and the glass slide. The findings of fiber movements were similar; when 3.5 μl of triacetin was used for the mDT slides, fiber movements were not detected, while fibers on slides prepared with 10 μl triacetin (mDT-10) moved around. No fiber movements were observed for the mDE slides at any time during 59 weeks. Once fiber movement started, fibers moved over distances measured from 4 μm and up to >1000 μm within 22 weeks. However, since then, no further fiber movements have been observed in any field sample slides. Additional sample slides, two Amosite and two chrysotile, were prepared from Union for International Cancer Control (UICC) samples using the AT method with 5 μl triacetin mounting medium. Fiber movements were also observed in these samples; chrysotile fibers began to migrate in 3 weeks, while Amosite fiber movement started after 3 months. Although fiber movement was observed for the AT-10, AE, and mDT-10 sample slides, fiber counts were not significantly different from AT-3.5 and mDE samples that exhibited no fiber movement. Although fiber counts would not be significantly changed by fiber movement, the type and amount of mounting medium for sample slide preparation remains critical for issues such as quality assurance and training of analysts by revisiting the same fibers.
Counting rules for estimating concentrations of long asbestos fibers. K.S. Crump, D.W. Berman. 2011;55(7):723-35. PubMed · Publisher

Abstract

Mounting evidence that long asbestos fibers (e.g. >20 or even 40 μm) pose the greatest cancer risk underscores the need for accurate measurement of concentrations of such fibers. These fiber lengths are of the same order of magnitude as the size of openings in the grids (typically ≈90 μm per side) used to analyze asbestos samples by transmission electron microscopy. This means that a substantial proportion of long fibers will cross the edge of a grid opening (GO) and therefore not be completely visible. Counting rules generally deal with such fibers by assigning a length equal to twice the visible length. Using both theoretical and simulation methods, we show that this doubling rule introduces bias into estimates of fiber concentrations and the amount of bias increases with fiber length. We investigate an alternative counting rule that counts only fibers that lie completely within a GO and weights those fibers by the reciprocal of the probability that a fiber of that length lies totally within a GO. This approach does not have the bias inherent in the doubling rule and is essentially unbiased if the stopping rule specifies a fixed number of GOs to be scanned. However, a stopping rule based on successively scanning GOs until a fixed number of fibers have been counted will introduce bias into any counting method, although this bias may typically not be large enough to be of practical concern. We recommend use of the weighted approach as a supplement to use of the doubling rule when estimating concentrations of long fibers, irrespective of the stopping rule employed.
Measuring mixed cellulose ester (MCE) filter mass under variable humidity conditions. K.T. Bogen, G. Brorby, D.W. Berman, et al. 2011;55(5):485-94. PubMed · Publisher

Abstract

Mixed cellulose ester (MCE) filters, used routinely to collect dust samples from air for fiber analysis, are the only filter type that can be prepared for both phased contrast microscopy and transmission electron microscopy analyses. However, whenever fiber counts require collecting dust masses <100 μg on a single filter under variable relative humidity (RH) conditions, historically noted effects of humidity on MCE filter mass can hinder accurate estimates of dust mass, measured as loaded minus unloaded filter mass (M). In this study, a baseline set of hundreds of paired measures of change in RH versus M over different time intervals were obtained over a 5-day period for replicate series of 40 unloaded 37-mm MCE filters under varying RH conditions at a nearly constant temperature. Similar baseline data were obtained for 25-mm MCE filters. Linear regressions fit to these data allow improved estimates of dust mass loaded onto MCE filters from measures of M and RH made before and after loading occurs. Using established theory, these relationships were generalized to address temperature variation as well, and examples of numerical applications are provided.
Mesothelioma in a connecticut friction plant: the need for transparency and exposure information in attribution of risk. M.J. Teta. 2011;55(7):817-9; author reply 820-2. Letter · Comment PubMed · Publisher
The effect of smoking on the risk of lung cancer mortality for asbestos workers in Great Britain (1971-2005). G. Frost, A. Darnton, A.H. Harding. 2011;55(3):239-47. PubMed · Publisher

Abstract

Objectives: Workers in the asbestos industry tend to have high smoking rates compared to the general population. Both asbestos exposure and cigarette smoking are recognized risk factors for lung cancer mortality, but the exact nature of the interaction between the two remains uncertain. The aim of this study was to examine the effect of smoking and smoking cessation among asbestos workers in Great Britain (GB) and investigate the interaction between asbestos exposure and smoking.

Methods: The study population consisted of 98 912 asbestos workers recruited into the GB Asbestos Survey from 1971, followed-up to December 2005. Poisson regression was used to estimate relative risks of lung cancer mortality associated with smoking habits of the asbestos workers and to assess whether these effects differed within various categories of asbestos exposure. The interaction between asbestos exposure and smoking was examined using the Synergy (S) and Multiplicativity (V) indices, which test the hypotheses of additive and multiplicative interaction, respectively. The proportion of lung cancers among smokers attributable to the interaction of asbestos and smoking was also estimated.

Results: During 1 780 233 person-years of follow-up, there were 1878 deaths from lung cancer (12% of all deaths). Risk of lung cancer mortality increased with packs smoked per day, smoking duration, and total smoke exposure (pack-years). Asbestos workers who stopped smoking remained at increased risk of lung cancer mortality up to 40 years after smoking cessation compared to asbestos workers who never smoked. The effects of smoking and stopping smoking did not differ by duration of asbestos exposure, main occupation, age at first asbestos exposure, year of first exposure, or latency period. The interaction between asbestos exposure and smoking for asbestos workers was greater than additive [S 1.4, 95% confidence interval (CI) 1.2-1.6], and the multiplicative hypothesis could not be rejected (V 0.9, 95% CI 0.3-2.4). For those asbestos workers who smoked, an estimated 26% (95% CI 14-38%) of lung cancer deaths were attributable to the interaction of asbestos and smoking.

Conclusions: This study emphasizes the importance of smoking prevention and cessation among those who work in the asbestos industry.
The risk of asbestos exposure in South African diamond mine workers. G. Nelson, J. Murray, J.I. Phillips. 2011;55(6):569-77. PubMed · Publisher

Abstract

Objectives: Asbestos is associated with South African diamond mines due to the nature of kimberlite and the location of the diamond mines in relation to asbestos deposits. Very little is known about the health risks in the diamond mining industry. The objective of this study was to explore the possibility of asbestos exposure during the process of diamond mining.

Methods: Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis were used to identify asbestos fibres in the lungs of diamond mine workers who had an autopsy for compensation purposes and in the tailings and soils from three South African diamond mines located close to asbestos deposits. The asbestos lung fibre burdens were calculated. We also documented asbestos-related pathological findings in diamond mine workers at autopsy.

Results: Tremolite-actinolite asbestos fibres were identified in the lungs of five men working on diamond mines. Tremolite-actinolite and/or chrysotile asbestos were present in the mine tailings of all three mines. Mesothelioma, asbestosis, and/or pleural plaques were diagnosed in six diamond mine workers at autopsy.

Conclusions: These findings indicate that diamond mine workers are at risk of asbestos exposure and, thus, of developing asbestos-related diseases. South Africa is a mineral-rich country and, when mining one commodity, it is likely that other minerals, including asbestos, will be accidentally mined. Even at low concentrations, asbestos has the potential to cause disease, and mining companies should be aware of the health risk of accidentally mining it. Recording of comprehensive work histories should be mandatory to enable the risk to be quantified in future studies.
Comparison of direct and indirect methods of measuring airborne chrysotile fibre concentration. C. Eypert-Blaison, S. Veissiere, O. Rastoix, et al. 2010;54(1):55-67. PubMed · Publisher

Abstract

Transmission electron microscopy observations most frequently form a basis for estimating asbestos fibre concentration in the environment and in buildings with asbestos-containing materials. Sampled fibres can be transferred to microscope grids by applying either a direct [ISO (1995) Draft International ISO/DIS 10312. Ambient air. Determination of asbestos fibres. Direct transfer transmission electron microscopy procedure. Geneva, Switzerland: International Standardization Organization] or an indirect [AFNOR (1996) Détermination de la concentration en fibres d'amiante par microscopie électronique à transmission-Méthode indirecte. Cedex, France: AFNOR, p. 42; ISO (1997) Draft International ISO/DIS 13794. Ambient air. Determination of asbestos fibres. Indirect-transfer transmission electron microscopy procedure. Geneva, Switzerland: International Standardization Organization] method. In the latter case, ISO Standard 13794 recommends filtering calcination residues either on a polycarbonate (PC) filter (PC indirect method) or on a cellulose ester (CE) membrane (CE indirect method). The PC indirect method requires that fibres deposited on a PC filter be covered by a carbon layer, whereas in the CE indirect method, the CE membrane has to be directly processed using a method described in ISO Standard 10312. The purpose of this study was to compare results obtained using, on the one hand, direct preparation methods and, on the other hand, PC indirect or CE indirect methods, for counting asbestos fibres deposited on filters as a result of liquid filtration or air sampling. In direct method-based preparation, we observed that an etching time of 6-14 min does not affect the measured densities, except for fibres <1 microm deposited by liquid filtration. Moreover, in all cases, the direct method gives higher densities than the PC indirect method because of possible fibre disappearance when using the carbon evaporator implemented in the PC indirect method. The CE membrane used for sample preparation in the CE indirect method is collapsed prior to passing it through the carbon evaporator, so the fibres are less likely to disappear at this stage. We then note that the resulting fibre densities for chrysotile-loaded filters prepared using the direct method are close to those obtained with filters prepared using the CE indirect method. Our study therefore shows that, under the implemented experimental conditions, the PC and CE indirect preparation methods described in ISO Standard 13794 are not equivalent.
Epidemiology of malignant mesothelioma--an outline. J.C. McDonald. 2010;54(8):851-7. PubMed · Publisher

Abstract

In the 1960s and 1970s, well designed case-referent studies put beyond doubt that exposure to airborne asbestos fibres was a cause of malignant mesothelioma. Some 35 cohort mortality studies in a large variety of industries during the 20-year period, 1974-1994, showed a wide range of outcomes, but in general that the risk was higher in exposures which included amphiboles rather than chrysotile alone. Real progress began, however, with discoveries along several lines: the link between pleural changes and mineralogy, the concept and importance of biopersistence, the developments in counting and typing mineral fibres in lung tissue, and data on amphibole mining in South Africa and Australia for comparison with that on chrysotile in Canada and Italy. This led to the recognition of the potential contamination in North America of chrysotile with tremolite. A survey in Canada in 1980-1988 and other surveys demonstrated that crocidolite, amosite, and tremolite could explain almost all cases of mesothelioma. Effective confirmation of this was finally achieved with data on vermiculite miners in Libby, Montana, in the years 1983-1999, where exposure was to tremolite-actinolite and/or other amphibole fibres alone.
In vitro cytotoxicity and transforming potential of industrial carbon dust (fibers and particles) in syrian hamster embryo (SHE) cells. C. Darne, F. Terzetti, C. Coulais, et al. 2010;54(5):532-44. PubMed · Publisher

Abstract

Carbon fibers have many applications, mainly in high-tech industries such as the aviation industry. Eleven carbon samples (fibers and particles) coming from an aeronautic group were tested for their cytotoxicity and carcinogenic potential using in vitro short-term assays in Syrian hamster embryo cells. These samples were taken during each important step of the process, i.e. from the initial heating of polyacrylonitrile fibers to pure carbon fibers. They were compared to an asbestos fiber, an amorphous silica, and two commercial graphite powders. Their physical-chemical characteristics and their capacity to release reactive oxygen species (ROS) were determined. This study showed that none of the carbon samples was able to generate ROS as measured by Electron Paramagnetic Resonance analysis, and in our biological assays, they demonstrated no morphological transformation potential and low cytotoxicity compared to positive control (chrysotile asbestos).
Malignant mesothelioma among employees of a Connecticut factory that manufactured friction materials using chrysotile asbestos. M.M. Finkelstein, C. Meisenkothen. 2010;54(6):692-6. Case report PubMed · Publisher

Abstract

There is ongoing argument about the potency of chrysotile asbestos to cause malignant mesothelioma. Risk assessment for chrysotile is influenced by the alleged absence of mesotheliomas among workers at the Raybestos Manhattan friction products plant in Connecticut, a plant that essentially used only chrysotile asbestos. Regrettably, the statement that there is an absence of mesothelioma deaths in the Connecticut plant is false. In this paper, we report on our review of the work histories and pathological reports of five individuals from the Connecticut plant who were diagnosed with mesothelioma. We discuss the Connecticut plant in relation to the most recent epidemiological information for chrysotile. Calculation suggests that mesothelioma rates at this plant were similar to those observed among Quebec miners and the South Carolina textile plant. We urge everyone concerned with the risk assessment of chrysotile asbestos to make use of all available data.
Malignant mesothelioma in a patient with anthophyllite asbestos fibres in the lungs. J.I. Phillips, J. Murray. 2010;54(4):412-6. Case report PubMed · Publisher

Abstract

The amphibole asbestos, anthophyllite, is associated with asbestos-related disease in humans, along with mesothelioma in animal models. In humans, however, there are only three cases of histologically proven malignant mesothelioma of the pleura associated with anthophyllite that have been documented in the English-language literature. A fourth case is presented in a man who lived in South Africa and had anthophyllite in his lung. Anthophyllite was never commercially mined in South Africa. Using scanning electron microscopy, his lung fibre burden was calculated to be 358,000 fibres and 31,000 asbestos bodies per gram of dry weight of lung tissue. The mean aspect ratio of the anthophyllite fibres in the lung was 41.2 (SD = 28.8). No other types of asbestos were detected in the lung. His exposure was almost certainly occupational. He worked in the plastic manufacturing industry and was exposed to talc and asbestos blankets that were used to insulate machinery.
Producing samples for the organization of proficiency tests. Study of the homogeneity of replicas produced from two atmosphere generation systems. L. Freville, J.C. Moulut, M. Grzebyk, et al. 2010;54(6):659-70. PubMed · Publisher

Abstract

This article describes two atmosphere generation systems used for the production of replicas. The first, the Sputnic system, is based on the Sputnic air sampler developed by the National Institute of Occupational Health in Oslo (Norway). It is used to generate asbestos fibres or silica particles and allows the simultaneous production, by means of sampling on filters, of up to 114 replicas. The second is a multipurpose system that allows dust sampling on foams used with the CIP 10-R device. Twenty samples can be taken simultaneously. In total, 120 series of samples allowed characterization of the variability of the two generation systems used for the production of replicas loaded with asbestos fibres or silica dust. The coefficients of variation characterizing the dispersion of the filter loading in the Sputnic system are <10% for high densities asbestos fibre or silica dust samples. The coefficient of dispersion is on average higher when the asbestos fibre density is lower. The differences observed between the measurements taken on the different crowns of the Sputnic system are low and <2%. The results obtained with the multipurpose system show that replica dispersion is on average equal to 4%, which will allow proposal in the near future of a proficiency test dedicated to the quantitative analysis of crystalline silica on foams sampled with the CIP 10-R device.
Simulation tests to assess occupational exposure to airborne asbestos from artificially weathered asphalt-based roofing products. P. Sheehan, F. Mowat, R. Weidling, et al. 2010;54(8):880-92. PubMed · Publisher

Abstract

Historically, asbestos-containing roof cements and coatings were widely used for patching and repairing leaks. Although fiber releases from these materials when newly applied have been studied, there are virtually no useful data on airborne asbestos fiber concentrations associated with the repair or removal of weathered roof coatings and cements, as most studies involve complete tear-out of old roofs, rather than only limited removal of the roof coating or cement during a repair job. This study was undertaken to estimate potential chrysotile asbestos fiber exposures specific to these types of roofing products following artificially enhanced weathering. Roof panels coated with plastic roof cement and fibered roof coating were subjected to intense solar radiation and daily simulated precipitation events for 1 year and then scraped to remove the weathered materials to assess chrysotile fiber release and potential worker exposures. Analysis of measured fiber concentrations for hand scraping of the weathered products showed 8-h time-weighted average concentrations that were well below the current Occupational Safety and Health Administration permissible exposure limit for asbestos. There was, however, visibly more dust and a few more fibers collected during the hand scraping of weathered products compared to the cured products previously tested. There was a notable difference between fibers released from weathered and cured roofing products. In weathered samples, a large fraction of chrysotile fibers contained low concentrations of or essentially no magnesium and did not meet the spectral, mineralogical, or morphological definitions of chrysotile asbestos. The extent of magnesium leaching from chrysotile fibers is of interest because several researchers have reported that magnesium-depleted chrysotile fibers are less toxic and produce fewer mesothelial tumors in animal studies than normal chrysotile fibers.
The diesel exhaust in miners study: I. Overview of the exposure assessment process. P.A. Stewart, J.B. Coble, R. Vermeulen, et al. 2010;54(7):728-46. PubMed · Publisher · Free full text

Abstract

This report provides an overview of the exposure assessment process for an epidemiologic study that investigated mortality, with a special focus on lung cancer, associated with diesel exhaust (DE) exposure among miners. Details of several components are provided in four other reports. A major challenge for this study was the development of quantitative estimates of historical exposures to DE. There is no single standard method for assessing the totality of DE, so respirable elemental carbon (REC), a component of DE, was selected as the primary surrogate in this study. Air monitoring surveys at seven of the eight study mining facilities were conducted between 1998 and 2001 and provided reference personal REC exposure levels and measurements for other agents and DE components in the mining environment. (The eighth facility had closed permanently prior to the surveys.) Exposure estimates were developed for mining facility/department/job/year combinations. A hierarchical grouping strategy was developed for assigning exposure levels to underground jobs [based on job titles, on the amount of time spent in various areas of the underground mine, and on similar carbon monoxide (CO, another DE component) concentrations] and to surface jobs (based on the use of, or proximity to, diesel-powered equipment). Time trends in air concentrations for underground jobs were estimated from mining facility-specific prediction models using diesel equipment horsepower, total air flow rates exhausted from the underground mines, and, because there were no historical REC measurements, historical measurements of CO. Exposures to potentially confounding agents, i.e. respirable dust, silica, radon, asbestos, and non-diesel sources of polycyclic aromatic hydrocarbons, also were assessed. Accuracy and reliability of the estimated REC exposures levels were evaluated by comparison with several smaller datasets and by development of alternative time trend models. During 1998-2001, the average measured REC exposure level by facility ranged from 40 to 384 μg m⁻³ for the underground workers and from 2 to 6 μg m⁻³ for the surface workers. For one prevalent underground job, 'miner operator', the maximum annual REC exposure estimate by facility ranged up to 685% greater than the corresponding 1998-2001 value. A comparison of the historical CO estimates from the time trend models with 1976-1977 CO measurements not used in the modeling found an overall median relative difference of 29%. Other comparisons showed similar levels of agreement. The assessment process indicated large differences in REC exposure levels over time and across the underground operations. Method evaluations indicated that the final estimates were consistent with those from alternative time trend models and demonstrated moderate to high agreement with external data.

2000s

Airborne asbestos concentrations associated with heavy equipment brake removal. A.K. Madl, S.H. Gaffney, J.L. Balzer, et al. 2009;53(8):839-57. PubMed · Publisher

Abstract

Asbestos-containing brake linings were used in heavy-duty construction equipment such as tractors, backhoes, and bulldozers prior to the 1980s. While several published studies have evaluated exposures to mechanics during brake repair work, most have focused on automobiles and light trucks, not on heavy agricultural or construction vehicles. The purpose of this study is to characterize the airborne concentration of asbestos to workers and bystanders from brake wear debris during brake removal from 12 loader/backhoes and tractors manufactured between 1960 and 1980. Asbestos content in brake lining (average 20% chrysotile by polarized light microscopy) and brake wear debris [average 0.49% chrysotile by transmission electron microscopy (TEM)] was also quantified. Breathing zone samples on the lapel of mechanics (n = 44) and area samples at bystander (n = 34), remote (n = 22), and ambient (n = 12) locations were collected during 12 brake changes and analyzed using phase contrast microscopy (PCM) [National Institute for Occupational Safety and Health (NIOSH) 7400] and TEM (NIOSH 7402). In addition, the fiber distribution by size and morphology was evaluated according to the International Organization for Standardization method for asbestos. Applying the ratio of asbestos fibers:total fibers (including non-asbestos) as determined by TEM to the PCM results, the average airborne chrysotile concentrations (PCM equivalent) were 0.024 f/cc for the mechanic and 0.009 f/cc for persons standing 1.2-3.1 m from the activity during the period of exposure ( approximately 0.5 to 1 h). Considering the time involved in the activity, and assuming three brake jobs per shift, these results would convert to an average 8-h time-weighted average of 0.009 f/cc for a mechanic and 0.006 f/cc for a bystander. The results indicate that (i) the airborne concentrations for worker and bystander samples were significantly less than the current occupational exposure limit of 0.1 f/cc; (ii) approximately 2% of respirable fibers were >20 microm in length; and (iii) approximately 95% of chrysotile in the brake linings degraded in the friction process. The industrial hygiene data presented here should be useful for conducting retrospective and current exposure assessments of individuals, as well as hazard assessments of work activities that involve repairing and replacing asbestos-containing brakes in heavy construction equipment.
Canadian chrysotile report released--at last. T.L. Ogden. 2009;53(4):307-9. Editorial PubMed · Publisher

Summary

This editorial, by the chair of an expert panel convened by Health Canada, described the delayed release of the panel's reports on the risks of chrysotile asbestos. In November 2007 Health Canada brought together experts who had previously expressed very different views on chrysotile, to see what degree of consensus existed. The reports were delivered in March 2008. They were released only on 9 April 2009, after several applications under the Canadian Access to Information Act. The author speculated that the delay was due to a perceived threat to Canadian chrysotile production. The panel's main discussion compared two meta-analyses of exposure–response relationships, by Hodgson and Darnton (2000) and by Berman and Crump (2003 draft). The author outlined differences between them, including how they handled tremolite contamination, linear versus non-linear models, and inclusion of the Charleston textile cohort. Despite these differences, the two analyses agreed to within an order of magnitude. A worker with a cumulative chrysotile exposure of 1 f-year/ml had an estimated probability of the order of 1 in 10 000 of dying of cancer due to the exposure. Both analyses concluded that amphiboles were many times more likely than chrysotile to cause mesothelioma. The panel supported both approaches but did not specifically endorse their figures, and two members recorded reservations. The author concluded that chrysotile risk was still a political issue, but that wide agreement existed on the science.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Comments on Asbestos fibre concentrations in the lungs of brake workers: another look. V.L. Roggli, T.A. Sporn, B.W. Case, et al. 2009;53(2):191; author reply 192-3. Comment · Letter PubMed · Publisher

Summary

In this letter to the editor, Roggli, Sporn, Case and Butnor responded to a 2008 article by Finkelstein, 'Asbestos Fiber Concentrations in the Lungs of Brake Workers: Another Look'. That article had criticized a 2003 study by Butnor et al. of lung mineral fiber analyses in 10 brake mechanics with malignant mesothelioma. The letter writers stated that neither Finkelstein nor his reviewers had carefully read the 2003 paper. They pointed out that the 2003 paper had reported, in its tables and text, that 3 of the 10 brake mechanic mesothelioma patients had elevated levels of either chrysotile or non-commercial amphibole asbestos fibers, and that one case had elevated levels of both. They argued that the group's average level of these fibers might therefore be expected to exceed the average of the 20 controls, so Finkelstein's findings were neither novel nor unexpected. They further stated that every case with elevated chrysotile or non-commercial amphibole fibers also had elevated levels of commercial amphibole fibers (amosite or crocidolite). Neither of these fiber types was used in friction products in the US. They concluded that these brake mechanics must have had another, unidentified source of asbestos exposure, and that the chrysotile or non-commercial amphibole fibers in these three cases should not be attributed to friction products. In their view, Finkelstein's findings were trivial and did not alter the conclusions of the 2003 study.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Retrospective exposure assessment for carcinogenic agents in bitumen waterproofing industry in Finland and denmark. P. Anttila, P. Heikkilä, M. Mäkelä, et al. 2009;53(2):139-51. PubMed · Publisher

Abstract

Objectives: The purpose of the study was (i) to identify the carcinogenic agents that may cause confounding when studying the exposure-response relationship between bitumen fume exposure and cancer among roofing membrane-manufacturing workers and roofers and (ii) to assess exposures to the identified carcinogens and bitumen fume in roofing membrane manufacturing and roofing in Finland and Denmark from 1950 to 2005.

Methods: Information on the use of carcinogenic agents and other relevant data were collected through semi-structured interviews of senior employees in the industry. Semi-quantitative exposure assessments were made on the basis of available measurement data and information obtained from the interviews and literature.

Results: Most of the production line workers in roofing membrane plants in Finland were exposed to asbestos until the mid-1970s. Also, some of the mixer operators in the plants were exposed to asbestos in Finland during the 1970s and in Denmark from the mid-1960s to the mid-1980s. In both countries, coal tar pitch was used in roofing membrane manufacturing until the mid-1960s, and consequently, exposure to polycyclic aromatic hydrocarbons (PAHs) in the plants was high in the 1950s and still significant in the early 1960s. Exposure of production line workers to quartz dust was high until the 1980s and is still relatively high compared with current occupational exposure limit values. Bitumen roofers' exposure to coal tar-derived PAHs may have been significant in both countries until the end of 1960s. Roofers' exposure to asbestos and quartz was estimated to have been near background level.

Conclusions: The estimated average annual exposures to asbestos, coal tar-derived PAHs and quartz dust in the bitumen waterproofing industry in Finland and Denmark were significant in the past but have a clear declining trend. Exposure to bitumen fume was found to follow a similar trend.
Risk assessment of the decay of asbestos cement roofs. A. Campopiano, D. Ramires, A.M. Zakrzewska, et al. 2009;53(6):627-38. PubMed · Publisher

Abstract

Objectives: In an assessment of the risk of asbestos fibres release from asbestos cement materials, an important role is played by the assessment of the surface corrosion and by the disaggregation of asbestos cement. The aim of this work is to evaluate the differences among several methods used for the risk assessment that lead to a specific choice of abatement techniques.

Methods: The state of deterioration of 40 asbestos cement roofs was evaluated using two priority assessment algorithms elaborated in Italy, the 'pull-up test' described by the Italian Organization for Standardization and the indicators described in the Italian legislation coupled with the observation of a small sample, taken from each roof, by a stereomicroscope.

Results: The results obtained with the methods, proposed in this study, for the risk assessment of the decay of asbestos cement roofs show slight differences among them, only one deviates from the others in judgement on the state of conservation of the roof.

Conclusions: It is very important to train the operator conducting the study since a completely subjectivity-free method does not exist. Whatever method is used will always be affected by the subjectivity linked to the competency and the training of the operator. Moreover, each method on its own cannot assess the risk of exposure to asbestos, but reliable assessment of asbestos-containing materials requires the use of more than one method, such as visual inspections, a pull-up test, and an assessment algorithm.
Role of associated mineral fibres in chrysotile asbestos health effects: the case of balangeroite. F. Turci, M. Tomatis, R. Compagnoni, et al. 2009;53(5):491-7. PubMed · Publisher

Abstract

Objectives: To evaluate the biodurability of balangeroite, present as contaminant of chrysotile asbestos in the Balangero mine, in order to have indication whether it might have been a confounding factor in the association of the mesothelioma cases reported among mine workers and employees.

Methods: The modifications taking place following incubation of the fibres in simulated phagolysosomal fluids have been measured on balangeroite, on one pure chrysotile sample (Val Malenco), on one chrysotile from Balangero with some associated balangeroite, and on two tremolite samples.

Results: The incubation modifies both chrysotile and balangeroite with substantial release in the medium of the metal ions which occupy the octahedral site in the mineral structure of the fibre while tremolite is virtually unaffected.

Conclusions: Considering the profound differences between the structure of balangeroite and amphiboles, previous results and observations on the poor ecopersistence of balangeroite, and the present data, we conclude that balangeroite traces may contribute to the overall toxicity of the airborne fibres in Balangero, but may not be compared to tremolite nor considered the sole responsible for the excess of mesothelioma found in Balangero.
Airborne concentrations of asbestos onboard maritime shipping vessels (1978-1992). D.M. Murbach, A.K. Madl, K.M. Unice, et al. 2008;52(4):267-79. PubMed · Publisher

Abstract

The exposure of shipyard workers to asbestos has been frequently investigated during the installation, repair or removal of asbestos insulation. The same level of attention, however, has not been directed to asbestos exposure of maritime seamen or sailors. In this paper, we assemble and analyze historical industrial hygiene (IH) data quantifying airborne asbestos concentrations onboard maritime shipping vessels between 1978 and 1992. Air monitoring and bulk sampling data were compiled from 52 IH surveys conducted on 84 different vessels, including oil tankers and cargo vessels, that were docked and/or at sea, but these were not collected during times when there was interaction with asbestos-containing materials (ACMs). One thousand and eighteen area air samples, 20 personal air samples and 24 air samples of unknown origin were analyzed by phase contrast microscopy (PCM); 19 area samples and six samples of unknown origin were analyzed by transmission electron microscopy (TEM) and 13 area air samples were analyzed by scanning electron microscopy (SEM). In addition, 482 bulk samples were collected from suspected ACMs, including insulation, ceiling panels, floor tiles, valve packing and gaskets. Fifty-three percent of all PCM and 4% of all TEM samples were above their respective detection limits. The average airborne concentration for the PCM area samples (n = 1018) was 0.008 fibers per cubic centimeter (f cc(-1)) (95th percentile of 0.040 f cc(-1)). Air concentrations in the living and recreational areas of the vessels (e.g. crew quarters, common rooms) averaged 0.004 f cc(-1) (95th percentile of 0.014 f cc(-1)), while air concentrations in the engine rooms and machine shops averaged 0.010 f cc(-1) (95th percentile of 0.068 f cc(-1)). Airborne asbestos concentrations were also classified by vessel type (cargo, tanker or Great Lakes), transport status (docked or underway on active voyage) and confirmed presence of ACM. Approximately 1.3 and 0% of the 1018 area samples analyzed by PCM exceeded 0.1 and 1 f cc(-1), respectively. This data set indicates that historic airborne asbestos concentrations on these maritime shipping vessels, when insulation-handling activities were not actively being performed, were consistently below contemporaneous US occupational standards from 1978 until 1992, and nearly always below the current permissible exposure limit of 0.1 f cc(-1).
Asbestos fibre concentrations in the lungs of brake workers: another look. M.M. Finkelstein. 2008;52(6):455-61. PubMed · Publisher

Abstract

Objective: To reanalyse data on the lung content of asbestos fibres among brake mechanics.

Methods: I re-analysed data published by Butnor, Roggli and colleagues on the lung content of chrysotile and tremolite asbestos fibres among brake mechanics and controls. Statistics of the distributions were estimated by maximum likelihood to accommodate observations below the detection limit. Mean concentrations were compared by the t-test, bootstrap resampling and interval-censored survival methods.

Results: The mean concentrations of fibres were higher among the brake workers than the controls. The concentration of tremolite fibres was higher than the concentration of chrysotile, a pattern similar to that observed among Quebec chrysotile miners and millers.

Conclusions: Re-analysis of published data does not support the interpretation that, in automotive brake repair workers with malignant mesothelioma, asbestos content is within the normal range. The alternative interpretation that brake mechanics have a greater than background burden of asbestos fibres, attributable to occupational exposure to dusts from friction products manufactured from Canadian chrysotile, appears more credible. This asbestos burden might be associated with an increased risk of asbestos-associated cancers.
Canada, chrysotile, and the search for truth. T. Ogden. 2008;52(8):673-4. Editorial PubMed · Publisher
Development of an exposure assessment method for epidemiological studies of New York State personnel who responded to the World Trade Center disaster. M.L. Herdt-Losavio, M.P. Mauer, G.A. Carlson. 2008;52(2):83-93. PubMed · Publisher

Abstract

Objectives: An exposure assessment method was developed for use in assigning an exposure score to New York State personnel who responded to the World Trade Center disaster site after the 11 September 2001 terrorist attacks.

Methods: The method consists of an algorithm with two instantiations. Each represents a major component of the overall exposures at the site: dust and smoke. The algorithm uses US Environmental Protection Agency air monitoring data collected between 23 September 2001 and 28 February 2002, as well as information on duration, location and time period of work assignment and type and frequency of personal protective respiratory equipment (PPE) use, collected by a self-administered mailed questionnaire. These data were used to calculate an overall exposure score for each participant. For each time period/location combination, individuals provided average number of hours and number of days worked. This was multiplied by a weighting factor derived from the median of the air monitoring data for the time period/location. Calcium was chosen as a surrogate for the dust exposure, so the weighting factors for the dust instantiation were calculated from calcium air monitoring data. Total hepta-chlorinated dibenzo-p-dioxin was chosen as a surrogate for the smoke exposure and was similarly used in the smoke instantiation.

Results: More individuals in the highest exposure score category performed tasks such as search/rescue and hand digging than those in the lowest exposure category. Also, those in the highest exposure category had a higher mean number of hours at the site than other exposure groups.

Conclusions: The exposure assessment method presented accounts for PPE use, amount of time at the site, proximity to the site and ambient air monitoring results taken in the immediate vicinity. The algorithm can be used to rank individuals in the same study with very different patterns of exposure, such as high-level, short-term exposures and low-level, long-term exposures. The concepts could be modified for use in other epidemiological studies where long-term chronic exposure is a concern.
Exposure to chrysotile asbestos associated with unpacking and repacking boxes of automobile brake pads and shoes. A.K. Madl, L.L. Scott, D.M. Murbach, et al. 2008;52(6):463-79. PubMed · Publisher

Abstract

Industrial hygiene surveys and epidemiologic studies of auto mechanics have shown that these workers are not at an increased risk of asbestos-related disease; however, concerns continue to be raised regarding asbestos exposure from asbestos-containing brakes. Handling new asbestos-containing brake components has recently been suggested as a potential source of asbestos exposure. A simulation study involving the unpacking and repacking of 105 boxes of brakes (for vehicles ca. 1946-80), including 62 boxes of brake pads and 43 boxes of brake shoes, was conducted to examine how this activity might contribute to both short-term and 8-h time-weighted average exposures to asbestos. Breathing zone samples on the lapel of a volunteer worker (n = 80) and area samples at bystander (e.g., 1.5 m from worker) (n = 56), remote area (n = 26) and ambient (n = 10) locations collected during the unpacking and repacking of boxes of asbestos-containing brakes were analyzed by phase contrast microscopy and transmission electron microscopy. Exposure to airborne asbestos was characterized for a variety of parameters including the number of boxes handled, brake type (i.e. pads versus shoes) and the distance from the activity (i.e. worker, bystander and remote area). This study also evaluated the fiber size and morphology distribution according to the International Organization for Standardization analytical method for asbestos. It was observed that (i) airborne asbestos concentrations increased with the number of boxes unpacked and repacked, (ii) handling boxes of brake pads resulted in higher worker asbestos exposures compared to handling boxes of brake shoes, (iii) cleanup and clothes-handling tasks produced less airborne asbestos than handling boxes of brakes and (iv) fiber size and morphology analysis showed that while the majority of fibers were free (e.g. not associated with a cluster or matrix), <30% were respirable and even fewer were of the size range (>20 microm length) considered to pose the greatest risk of asbestos-related disease. It was found that average airborne chrysotile concentrations (30 min) ranged from 0.086 to 0.368 and 0.021 to 0.126 f cc(-1) for a worker unpacking and repacking 4-20 boxes of brake pads and 4-20 boxes of brake shoes, respectively. Additionally, average airborne asbestos exposures (30 min) at bystander locations ranged from 0.004 to 0.035 and 0.002 to 0.011 f cc(-1) when 4-20 boxes of brake pads and 4-20 boxes of brake shoes were handled, respectively. These data show that a worker handling a relatively large number of boxes of brakes over short periods of time will not be exposed to airborne asbestos in excess of its historical or current short-term occupational exposure limits.
Linking expert judgement and trends in occupational exposure into a job-exposure matrix for historical exposure to asbestos in the Netherlands. P. Swuste, M. Dahhan, A. Burdorf. 2008;52(5):397-403. PubMed · Publisher

Abstract

The aim of this article was to describe the structure and content of a job-exposure matrix (JEM) for historical asbestos exposure in The Netherlands. The JEM contained 309 occupational job title groups in 70 branches of industry during 10 periods of 5 years during 1945-1994, resulting in 3090 evaluations. Dutch sources on asbestos exposure measurements provided quantitative guidance for 69 evaluations (2.2%) in 25 occupational title groups. In addition, three databases from the UK Health and Safety Executive contributed to 222 evaluations (7.2%) and several other sources aided in another 133 evaluations (4.3%). These evaluations resulted in seven categories of exposure levels for all 3090 combinations of occupational title groups and periods. A verification process with five experts was used to adjust the assignments of exposure categories. The trends in exposure patterns over time were described in relation to production activities, operational control measures and the presence of dust control measures. For the majority of asbestos-related diseases in the past decades, reliable information on their historical exposure patterns was lacking. The limited availability of exposure measurements in the past illustrates the need for a structured assessment of historical asbestos exposure through a JEM.
A case control study of lung cancer and exposure to chrysotile and amphibole at a slovenian asbestos-cement plant. M. Dodic Fikfak, D. Kriebel, M.M. Quinn, et al. 2007;51(3):261-8. PubMed · Publisher

Abstract

A lung cancer case-control study was conducted in a Slovenian asbestos-cement factory for which unusually good records of asbestos exposures were available. The cohort consisted of all 6714 workers employed at the Salonit Anhovo factory after 31 December 1946 who worked there for at least one day between 1964 and 1994. Fifty-eight histologically confirmed cases of primary lung cancer and 290 controls were selected from the cohort. Working life exposure histories to amphibole and chrysotile forms of asbestos were estimated separately. Airborne asbestos concentrations were low. For example, the arithmetic mean exposure to all forms of asbestos in the highest exposure period (1947-1971) was 1.2 f/cm(3). Chrysotile asbestos made up about 90% of this exposure (mean 1.1 f/cm(3)), whereas amphibole accounted for 10% (0.1 f/cm(3)). Comparing those above and below the 90 percentile of cumulative exposure, the odds ratios for all asbestos, chrysotile and amphibole were 1.5, 1.6 and 2.0, respectively, but confidence intervals were wide. There are only a few asbestos-lung cancer studies with high-quality exposure data and exposures in this low range. Though imprecise, the findings are important to the ongoing debate about asbestos risks.
Evaluation of a national register on occupational exposure to carcinogens: effectiveness in the prevention of occupational cancer, and cancer risks among the exposed workers. T. Kauppinen, A. Saalo, E. Pukkala, et al. 2007;51(5):463-70. PubMed · Publisher

Abstract

Objectives: The objective of this study was to evaluate the performance and effectiveness of a register of employees exposed to carcinogens (the ASA Register) which has been in operation in Finland since 1979, and to study cancer risks among the notified workers.

Methods: The impact of ASA at workplaces was studied by questionnaires mailed to 1448 work departments, which were notified to ASA in 1996, and to 1033 departments, which departed ASA in 1991-1996. The mailing was responded by 69% of departments. The cancer incidence of 35,138 workers notified to ASA in 1979-1988 was followed up through the files of the Finnish Cancer Register for the period 1980-2003.

Results: Changes eliminating or substantially reducing exposure to carcinogens were reported by 73% of departments notified to ASA in 1996. The ASA notification process had directly prompted measures to reduce exposure (8% of cases) or contributed to them (24% of cases). Estimations based on responses of the workplaces suggested that the ASA registration had decreased exposure of 600 workers year(-1) (out of approximately 15,000 notified workers, which is <1% of the employed in Finland), preventing thereby an unknown number of occupational cancers. Other benefits of ASA included the saving of the treatment costs of prevented cancers, the prevention of other health outcomes of carcinogens, improved safety behaviour of exposed workers and avoidance of human suffering among cancer patients and their families. The labour safety authorities had better possibilities to direct their activities against carcinogen exposure. These benefits should be considered against the annual costs, mainly due to 7-8 person-years of work required by tasks related to ASA. The results of the cancer incidence study among notified workers were based on a relatively short follow-up (on average 19 years). The incidence of mesothelioma was significantly increased in the ASA cohort, probably due to exposure to asbestos.

Conclusions: These results suggest that a national exposure register may stimulate preventive measures at workplaces. Partially based on the results of the present study the Finnish Ministry of Social Affairs and Health continues ASA registration.
Evaluation of asbestos exposures during firewood-harvesting simulations in Libby, MT, USA--preliminary data. J.F. Hart, T.J. Ward, T.M. Spear, et al. 2007;51(8):717-23. PubMed · Publisher

Abstract

Research was conducted in order to assess potential exposure to asbestos while harvesting firewood from amphibole-contaminated trees near Libby, MT, USA. Three firewood-harvesting simulations took place in the summer and fall of 2006 in the Kootenai Forest inside the US Environmental Protection Agency (EPA) restricted zone surrounding the former W.R. Grace vermiculite mine. Another simulation was conducted near Missoula, MT, USA, which served as the control. The work practices following each simulation were consistent throughout each trial. Personal breathing zone (PBZ) asbestos concentrations were measured by phase contrast microscopy (PCM) and transmission electron microscopy (TEM). Surface wipe samples of personal protective clothing were measured by TEM. The mean (n = 12) PBZ PCM sample time-weighted average (TWA) concentration was 0.29 fibers per milliliter, standard deviation (SD = 0.54). A substantial portion (more than five fibers per sample) of non-asbestos fibers (cellulose) was reported on all PBZ samples (excluding field blanks) when analyzed by TEM. The mean (n = 12) PBZ TEM sample TWA concentration for amphibole fibers <5-microm long was 0.15 fibers per milliliter (SD = 0.21) and the mean (n = 12) PBZ TEM concentration for amphibole fibers >5-microm long was 0.07 fibers per milliliter (SD = 0.08). Substantial amphibole fiber concentrations were revealed on Tyvek clothing wipe samples. The mean concentration (n = 12) was 29 826 fibers per square centimeter (SD = 37 555), with 91% (27 192 fibers per square centimeter) comprised fibers <5-microm long. There were no significant differences in PBZ and wipe sample concentrations among the tasks performed by four investigators. Each of these three simulations were consistent in demonstrating that amphibole fibers are released from tree reservoirs during firewood-harvesting activities in asbestos-contaminated areas and that the potential for exposure exists during such activities.
Exposure of UK industrial plumbers to asbestos, Part I: Monitoring of exposure using personal passive samplers. G. Burdett, D. Bard. 2007;51(2):121-30. PubMed · Publisher

Abstract

Epidemiological data suggest that there has been and may continue to be a significant risk to maintenance workers, who through their work may disturb asbestos-containing materials (ACM). The sampling and assessment of maintenance workers' exposure is a particular problem because they may not know that they are working with ACM. A strategy to monitor their true exposure has been developed and applied to one group of workers. The asbestos exposure of industrial plumbers was measured using personal passive samplers developed at the Health and Safety Laboratory (HSL). The light-weight samplers, which collect particles by electrostatic attraction, are simple to use and do not require prior knowledge that asbestos is to be disturbed as does conventional sampling. The samplers were issued by post and analysed, after return, using transmission electron microscopy (TEM). The strategy was found to be a reasonably efficient and cost-effective way to obtain data on maintenance worker's exposure to asbestos. The results of the TEM analysis of the passive samplers showed that the percentage of workers exposed to >5 microm long asbestos fibres was 62% in Round 1 and 58% in Round 2. For phase contrast microscopy equivalent (PCME) asbestos fibres, the values were 46 and 29%, respectively. The three samples with the highest numbers of fibres were followed up and were associated with plumbers working in areas which had supposedly been stripped of asbestos just prior to their starting work, suggesting that poor removal, clean-up and clearance practice presents a significant part of the risk to plumbers. Although flow rates will vary with conditions and time, an approximate average sampling rate from previous comparisons was used to calculate the concentration. This gave an average exposure to regulated PCME fibres of 0.009 f ml-1 for amphibole asbestos and 0.049 f ml-1 for chrysotile. The calculate risk based on the PCME fibre types collected and their estimated concentrations, showed that the risk from airborne amphibole fibres was approximately 6 times greater than from chrysotile fibres. If representative, the estimated lifetime risk of death from an asbestos related cancer for an exposure from age 20 for 40 years would be 68 per 100,000, which equates to an annual risk of death of the order of 10 per million.
Exposure of UK industrial plumbers to asbestos, Part II: Awareness and responses of plumbers to working with asbestos during a survey in parallel with personal sampling. D. Bard, G. Burdett. 2007;51(2):113-9. PubMed · Publisher

Abstract

Throughout the European Union, millions tonnes of asbestos were used in the manufacture of products for building and for industrial installations. Today, in the UK, it is estimated that over half a million non-domestic premises alone have asbestos-containing materials in them and it is recognized that those working in building maintenance trades continue to be at significant risk. In part II, the awareness of UK plumbers to when they are working with asbestos was investigated and compared with the monitored levels reported in part I. The plumbers were issued by post with passive samplers, activity logs to monitor a working week and a questionnaire. The activity logs were used to assess whether maintenance workers were knowingly or unknowingly exposed to airborne asbestos fibres during a course of a working week. The questionnaire was designed to gather information on their: age, employment status, current and past perception of the frequency which they work with asbestos and knowledge of the precautions that should be taken to limit exposure and risk. Approximately 20% of workers reported on the sample log that they had worked with asbestos. There was a high correlation (93%) between the sampling log replies that they were knowingly working with asbestos and measured asbestos on the passive sampler. However, some 60% of the samples had >5 microm long asbestos structures found by transmission electron microscopy (TEM) analysis suggesting that the plumbers were aware of about only one-third of their contacts with asbestos materials throughout the week. This increased to just over one half of the plumbers being aware of their contact based on the results for phase contrast microscopy (PCM) countable asbestos fibres. The results from the questionnaire found that over half of the plumbers replying thought that they disturb asbestos only once a year and 90% of them thought they would work with asbestos for<10 h year-1. Their expectations and awareness of work with asbestos were therefore far lower than found during the period of monitoring. The response to an open question on the precautions to be taken, found that 61% of plumbers would avoid disturbance and 59% would use respiratory protection if they did disturb asbestos. However, their awareness of the methods and the need to reduce their risk by control of emissions at source was very low and suggests that further awareness raising and training is needed. The survey was carried out prior to the introduction of the duty to manage and gives a useful baseline to assess the impact of regulatory initiatives.
Exposure to refractory ceramic fibres in the metal industry. M. Linnainmaa, J. Kangas, M. Mäkinen, et al. 2007;51(6):509-16. PubMed · Publisher

Abstract

Refractory ceramic fibres (RCF) are used in thermal isolation in the metal industry where high temperatures are regularly employed. Asbestos materials were earlier commonly used for these purposes. In this work, two Finnish steel plants, three foundries and a repair shop were studied for the ceramic fibre exposure of their workers under normal production and during the replacement of oven insulation. Personal and stationary sampling was used together with a novel nasal lavage sampling for the evaluation of personal exposure. Fibres were counted with optical and electron microscopy and they were identified using an energy-dispersive X-ray analyser. Ceramic fibres were found in most production phases [range <0.01-0.29 fibres per cubic centimetre (f cm(-3))]. Considerably higher fibre counts were obtained during the maintenance work (range <0.01-14.2 f cm(-3)). Nasal sampling was found to correlate with the airborne fibre concentrations at the group level. The mean fibre concentrations varied from 34 to 6680 f ml(-1) of lavage liquid. Use of personal respiratory protectors diminished the exposure on the average as analysed in the lavage specimens, but the effect of respirator use did not appear clearly in the results. Because of the heat conditions, the workers used the respirators for a strict minimum period. A considerable exposure to RCF occurs in the studied plants. Its risk should be evaluated and managed more closely in view that the material is carcinogenic. Use of personal respiratory protectors should be encouraged. Their effective use could be verified by the nasal sampling for fibres after the work shift.
Inter-rater agreement for a retrospective exposure assessment of asbestos, chromium, nickel and welding fumes in a study of lung cancer and ionizing radiation. E.A. Seel, D.D. Zaebst, M.J. Hein, et al. 2007;51(7):601-10. PubMed · Publisher

Abstract

A retrospective exposure assessment of asbestos, welding fumes, chromium and nickel (in welding fumes) was conducted at the Portsmouth Naval Shipyard for a nested case-control study of lung cancer risk from external ionizing radiation. These four contaminants were included because of their potential to confound or modify the effect of a lung cancer-radiation relationship. The exposure assessment included three experienced industrial hygienists from the shipyard who independently assessed exposures for 3519 shop/job/time period combinations. A consensus process was used to resolve estimates with large differences. Final exposure estimates were linked to employment histories of the 4388 study subjects to calculate their cumulative exposures. Inter-rater agreement analyses were performed on the original estimates to better understand the estimation process. Although concordance was good to excellent (78-99%) for intensity estimates and excellent (96-99%) for frequency estimates, overall simple kappa statistics indicated only slight agreement beyond chance (kappa < 0.2). Unbalanced distributions of exposure estimates partly contributed to the weak observed overall inter-rater agreement. Pairwise weighted kappa statistics revealed better agreement between two of the three panelists (kappa = 0.19-0.65). The final consensus estimates were similar to the estimates made by these same two panelists. Overall welding fume exposures were fairly stable across time at the shipyard while asbestos exposures were higher in the early years and fell in the mid-1970s. Mean cumulative exposure for all study subjects was 520 fiber-days cc(-1) for asbestos and 1000 mg-days m(-3) for welding fumes. Mean exposure was much lower for nickel (140 microg-days m(-3)) and chromium (45 microg-days m(-3)). Asbestos and welding fume exposure estimates were positively associated with lung cancer in the nested case-control study. The radiation-lung cancer relationship was attenuated by the inclusion of these two confounders. This exposure assessment provided exposure estimates that aided in understanding of the lung cancer-radiation relationship at the shipyard.
Measurement of asbestos fibre concentrations in fluid of repeated bro-choalveolar lavages of exposed workers. P. Sartorelli, R. Romeo, G. Scancarello, et al. 2007;51(5):495-500. PubMed · Publisher

Abstract

Objectives: The aim of this study was to assess the reliability of asbestos fibre concentration in bronchoalveolar lavage fluid (BALF) by carrying out the mineralogical analysis of BALF at different times in the same patient and comparing the results.

Methods: Twenty two patients underwent diagnostic fibreoptic bronchoscopy twice: the first was to assess the past asbestos exposure and the second for different clinical reasons. Mineralogical analysis of BALF was carried out.

Results: In 16 patients (72.7%), a reduction of concentration in BALF of all asbestos fibres was observed. The concentrations of both chrysotile and amphiboles in the first bronchoalveolar lavage (BAL) were related to their concentrations in the second BAL and the observed differences were not statistically significant. A significant decrease in asbestos body concentration between the first and the second BAL was found (Wilcoxon test, P < 0.01).

Conclusions: The reliability of the fibre concentration in BALF as a marker of past asbestos exposure seems quite good. In most cases, it allows us to distinguish workers in different classes of exposure and gives useful information on the pattern of exposure. Uncertainties related in general to lung residues and in particular to mineralogical analysis of BALF (mainly due to the high coefficient of variation (CV) at low fibre concentrations and the results of the statistical analysis on total fibres) suggest that this biomarker is more likely suitable for a qualitative/categorical approach to exposure assessment than a quantitative one.
Occupational exposure to mineral fibres: analysis of results stored on colchic database. E. Kauffer, R. Vincent. 2007;51(2):131-42. PubMed · Publisher

Abstract

The aim of this paper is to present fibre exposure data recorded on the COLCHIC database. This database consolidates all occupational exposure data collected in French companies by the Caisses Régionales d'Assurance Maladie (regional health insurance funds, CRAM) and the Institut National de Recherche et de Sécurité (national institute for research and safety, INRS). A total of 8029 concentration results, expressed in number of fibres measured by phase-contrast optical microscopy, are available for exposure to asbestos fibres, ceramic fibres and man-made mineral fibres other than ceramic fibres. Presentation of base data by activity branch, activity sector or workplace permits identification of situations, for which prevention efforts are most essential. Analysis of exposure levels during the 1986-2004 period show that these are broadly influenced by changes in the exposure limit values. Wearing of respiratory protection equipment by employees is also discussed. The data may be helpful to occupational physicians performing occupational screening of exposed workers and to epidemiologists seeking information for building job-exposures matrices. In this respect, a database (FIBREX) will be available on the INRS web site (www.inrs.fr) at the beginning of 2007. This database will provide a higher level of detail in activity and workplace description than that which was possible for practical reasons in this paper.
Simulation tests to assess occupational exposure to airborne asbestos from asphalt-based roofing products. F. Mowat, R. Weidling, P. Sheehan. 2007;51(5):451-62. PubMed · Publisher

Abstract

This study sought to evaluate exposure from specific products to evaluate potential risk from roof repair activities. Five asbestos-containing fibered roof coatings and plastic cements, representing a broad range of these types of products, were tested in exposure simulations. These products were applied to representative roof substrates. Release of asbestos fibers during application and sanding of the product shortly thereafter (wet sanding) were tested initially. Other roof substrates were cured to simulate a product that had been on a rooftop for several months and then were tested to evaluate release of fibers during hand sanding and hand scraping activities. Additional tests were also conducted to evaluate asbestos release during product removal from tools and clothing. Two personal (n = 84) and background/clearance (n = 49) samples were collected during each 30-min test and analyzed for total fiber concentration [phase-contrast microscopy (PCM)] and for asbestos fiber count [transmission electron microscopy (TEM)]. PCM concentrations ranged from <0.005 to 0.032 fibers per cubic centimeter (f cc(-1)). Chrysotile fibers were detected in 28 of 84 personal samples collected. TEM concentrations ranged from <0.0021 to 0.056 f cc(-1). Calculated 8-h time-weighted averages (TWAs) ranged from 0.0003 to 0.002 f cc(-1) and were comparable to the background TWA concentration of 0.0002 f cc(-1) measured in this study. Based on these results, it is unlikely that roofers were exposed to airborne asbestos concentrations above the current or historical occupational guidelines during scraping and sanding of these products during roof repair.
Case-control study on renal cell cancer and occupational exposure to trichloroethylene. Part I: Exposure assessment. J. Fevotte, B. Charbotel, P. Muller-Beauté, et al. 2006;50(8):765-75. PubMed · Publisher

Abstract

A method for a semi-quantitative retrospective assessment of exposure to trichloroethylene (TCE) was implemented for a case-control study conducted in the Arve valley (France), an area with a widely developed screw-cutting industry, where teams of occupational physicians have collected a large quantity of well-documented measurements. A task-exposure matrix was developed to link the main working circumstances in a screw-cutting workshop to corresponding TCE-exposure levels: a 'basic level' was assigned to each task, standing for usual working procedures; exposure circumstances, such as duration or distance from the TCE source, were introduced as corrective factors. In parallel, a detailed occupational questionnaire was designed, setting subjects' descriptions of their successive jobs and working circumstances against levels assessed in the matrix. Possible exposure to TCE, plus some other occupational compounds (other solvents, oils, some metals, asbestos, welding fumes and ionizing radiations), were assessed for any job in all job histories. An average level of exposure to TCE, related to an 8 h usual working day, was attributed to each job period in turn, which was then categorized into six classes: 0; 1-35; 35-50; 50-75; 75-100; and >100 p.p.m. A total of 402 study subjects described their occupational life (average 3.7 jobs/subject, from 1924 to 2003). About 19% of the 1486 job periods described were assessed as being exposed to TCE; of these, 72.2% involved levels<35 p.p.m., 13.2% involved levels>50 p.p.m. and 5.4% above the French occupational exposure limit of 75 p.p.m. (TWA 8 h). A total of 41 job periods included exposure with peaks. Compared with levels encountered in other studies, the more severely exposed part of our study population seemed more exposed than most other populations previously studied, owing to vapor degreasing practices.
Comments about the proposal to adapt the WASP programme to fibre counting tests. B. Préat. 2006;50(1):105. Comment · Letter PubMed · Publisher
Estimating the number of asbestos-related cancer deaths in Great Britain. M. Greenberg. 2006;50(1):107. Letter · Comment PubMed · Publisher
Estimating the number of asbestos-related lung cancer deaths in Great Britain from 1980 to 2000. A.J. Darnton, D.M. McElvenny, J.T. Hodgson. 2006;50(1):29-38. PubMed · Publisher

Abstract

Introduction: Inhalation of asbestos fibres is known to cause two main kinds of cancer-mesothelioma and lung cancer. While the vast majority of mesothelioma cases are generally accepted as being caused by asbestos, the proportion of asbestos-related lung cancers is less clear and cannot be determined directly because cases are not clinically distinguishable from those due to other causes. The aim of this study was to estimate the number of asbestos-related lung cancers among males by modelling their relative lung cancer mortality among occupations within Great Britain in terms of smoking habits, mesothelioma mortality (as an index of asbestos exposure) and occupation type (as a proxy for socio-economic factors).

Methods: Proportional mortality ratios for lung cancer and mesothelioma for the 20-year period from 1980 to 2000 (excluding 1981) were calculated for occupational groups. Smoking indicators were developed from three General Household Surveys carried out during the 1980s and 1990s. Poisson regression models were used to estimate the number of asbestos-related lung cancers by estimating the number of lung cancer deaths in each occupation assuming no asbestos exposure and subtracting this from the actual predicted number of lung cancer deaths.

Results: The effect of asbestos exposure in predicting lung cancer mortality was weak in comparison to smoking habits and occupation type. The proportion of current smokers in occupational groups and average age at which they started smoking were particularly important factors. Our estimate of the number of asbestos-related lung cancers was between two-thirds and one death for every mesothelioma death: equivalent to between 11 500 and 16 500 deaths during the time period studied.

Conclusions: Asbestos-related lung cancer is likely to have accounted for 2-3% of all lung cancer deaths among males in Great Britain over the last two decades of the 20th century. Asbestos-related lung cancers are likely to remain an important component of the total number of lung cancer deaths in the future as part of the legacy of past asbestos exposures in occupational settings.
Lung fibre burden in lung cancer cases employed in the rock and slag wool industry. K. Soldan, F.D. Pooley, J. Hansen, et al. 2006;50(3):241-8. PubMed · Publisher

Abstract

Objectives: To evaluate the relationship between estimated exposure to man-made vitreous fibres (MMVF) and to asbestos fibres and their concentration in the lung tissue of lung cancer cases amongst MMVF production workers.

Methods: Retrospective retrieval of available lung tissue specimens was conducted following a case-control study that assessed estimated occupational exposures of MMVF workers. Fibre recovery and analysis by transmission electron microscopy (TEM) were conducted to determine fibre type, fibre dimension and numbers per gram of dry lung tissue. For cases with detailed exposure data, geometric mean (GM) concentrations were compared across the exposure categories, and regression models were used to investigate the relationship between the lung fibres and the variables of estimated exposure, with and without additional variables that may affect fibre retention.

Results: A total of 24 samples from 17 cases of lung cancer were available for analysis: MMVF were detected in all cases. Asbestos fibres were detected in 16. No difference or trend in GM MMVF concentration was observed across the estimated exposure categories. Odds ratio (OR) for MMVF g(-1) dry lung was 0.5 (95% confidence interval: 0.1-2.4) for the second, and 3.5 (0.6-18.9) for the third quartile of index of average exposure to MMVF in industry, compared with the first (lowest exposed) quartile (no cases in the highest quartile).

Conclusions: No observable relationship existed between estimated exposure and directly-measured lung fibres among this sample of cases. Retrospective specimen collection, intra-individual variability in fibre concentration, effect of unknown factors on fibre retention and small sample size militated against this study providing evidence for or against a relationship between estimated exposure and lung fibre concentrations.
Proposal to adapt the WASP programme to fibre counting tests. M. Grzebyk, E. Kauffer, L. Fréville. 2006;50(4):427. Comment · Letter PubMed · Publisher
A comparison of fibre counting across three European national proficiency testing schemes. A.D. Jones, M.C. Arroyo, R. Grosjean, et al. 2005;49(4):309-24. PubMed · Publisher

Abstract

Proficiency testing (PT) schemes seek to improve and maintain consistency in asbestos fibre counting by circulating mounted samples to laboratories, which return counts for comparison with consensus reference values. This study compares the level of these consensus values in three (Spanish, Belgian and UK) national PT schemes. It also assesses the effect of the imminent change in the European standard rules for counting asbestos fibres, to the new rules from the World Health Organisation (WHO), which will include more fibres. Forty samples from the three schemes were circulated to six laboratories, two in each national scheme. The UK and Spanish laboratories counted using both the ERM and the WHO method. Belgian laboratories already use the WHO method, and they counted only by this method. Densities from counts in this sample exchange served as a common basis against which we compared the national reference values (R). This produced a geometric overall mean ratio of R to exchange mean density of 0.94 for the UK scheme, 1.01 for the Spanish and 0.97 for the Belgian scheme, and thus indicated remarkably similar levels. Nevertheless, non-trivial systematic inter-laboratory differences confirmed the need for regular PT and international inter-laboratory comparisons. Examination of previous data from the national PT schemes and from an international scheme (AFRICA) provided further comparisons for the same laboratories (either comparing the laboratory's data with R values or making direct comparisons between laboratories) that are consistent with those from this special exchange. The change in fibre counting rule (to include fibres apparently touching particles with diameter >3 microm) produced mean increases in reported densities that ranged among samples from 0 to 70% (highest individual estimate 170%); the effect was broadly similar for the three schemes. The laboratories gave mostly similar estimates of percentage increase; however, one laboratory occasionally produced high estimates indicating a possible need for training for using the new method.
Asbestos lung residue and asbestosis risk. R. Howie. 2005;49(1):95-7. Letter PubMed · Publisher
Asbestos lung residue and asbestosis risk. A. Rogers. 2005;49(4):363-4; author reply 364-5. Comment · Letter PubMed · Publisher
Mineral particles of varying composition induce differential chemokine release from epithelial lung cells: importance of physico-chemical characteristics. J. Ovrevik, T. Myran, M. Refsnes, et al. 2005;49(3):219-31. PubMed · Publisher

Abstract

Presently, little is known about the potential health effects of mineral particles other than asbestos and quartz. In this study, a human epithelial lung cell line (A549), primary human small airway epithelial cells (SAECs) and primary rat type 2 (T2) cells were exposed to stone quarry particles of two size fractions (<10 and <2.5 microm) from nine different rock samples. The ability to induce the release of chemokines from lung cells was investigated and compared with the particles' mineral and element composition and the amount of soluble elements. The stone particles induced the release of only low levels of interleukin (IL)-8 from A549 cells. In contrast, some of the other particles induced the release of high levels of macrophage inflammatory protein (MIP)-2 from T2 cells, and high levels of IL-8 from SAECs. Differences in particle surface area could account for differences in activity between the <10 and <2.5 microm fractions of six out of the nine rock samples. For two samples the <2.5 microm fraction was most active and for one sample the <10 microm fraction was most active. Content of the mineral plagioclase displayed a strong, negative correlation with the potential to induce MIP-2, whereas the mineral pyroxene was positively correlated with MIP-2 induction. However, neither plagioclase nor pyroxene content was sufficient to explain differences in bioactivity between the particles. No statistically significant correlation was found between the amounts of total or soluble elements and MIP-2 release. In conclusion, the results suggest that mineral particles with a high content of plagioclase have a low potential to induce a pro-inflammatory response. However, a particular mineral or element responsible for eliciting strong increases in chemokine release could not be identified. Thus, at present it appears that analysing mineral and element content is insufficient to predict stone particle bioactivity, and that biological testing is a necessity.
Mesothelioma and lung cancer among motor vehicle mechanics: a meta-analysis. M. Goodman, M.J. Teta, P.A. Hessel, et al. 2004;48(4):309-26. Meta-analysis · Systematic review PubMed · Publisher

Abstract

We conducted a systematic review and analysis of the epidemiological literature that examines the risk of lung cancer and mesothelioma among motor vehicle mechanics who may have been engaged in brake repair and, thus, were potentially exposed to asbestos. All relevant studies were classified into three tiers according to their quality. Tier III (lowest quality) studies were cited for completeness, but were not included in the meta-analysis. Meta relative risks (meta-RRs) were calculated for mesothelioma and lung cancer using both fixed and random effects models for Tiers I and II, separately, followed by stratified analyses based on study design or exposure characterization (garage workers versus brake workers) and, for lung cancer studies, based on adequate adjustment for smoking. The meta-analysis for Tier I (higher quality) and Tier II (lower quality) studies of mesothelioma yielded RR estimates of 0.92 (95% CI 0.55-1.56) and 0.81 (95% CI 0.52-1.28), respectively. Further stratification according to exposure characterization did not affect the results. The meta-analysis for lung cancer produced RR estimates of 1.07 (95% CI 0.88-1.31) for Tier I and 1.17 (95% CI 1.01-1.36) for Tier II. When the lung cancer analysis was limited to studies that used adequate control for smoking, the resulting RR estimate was 1.09 (95% CI 0.92-1.28). Based on these findings, we conclude that employment as a motor vehicle mechanic does not increase the risk of developing mesothelioma. Although some studies showed a small increase in risk of lung cancer among motor vehicle mechanics, the data on balance do not support a conclusion that lung cancer risk in this occupational group is related to asbestos exposure.
The interaction of asbestos and smoking in lung cancer: a modified measure of effect. G. Berry, F.D. Liddell. 2004;48(5):459-62. PubMed · Publisher

Abstract

Objectives: The ratio of the relative risk of lung cancer due to asbestos exposure in non-smokers to that in smokers has been termed the relative asbestos effect (RAE). In a review, Liddell [Liddell FDK (2001) Ann Occup Hyg; 45: 341-56] estimated that the RAE was approximately 2. This measure is satisfactory when there is an appreciable relative risk due to asbestos but does not generalize to lower levels of exposure. A modified measure is proposed to overcome this difficulty. The modified measure, RAEm, is defined as the ratio of the excess relative risk (RR - 1) in non-smokers to that in smokers.

Methods: The cohort studies combined in Liddell's 2001 analysis have been used to give a combined estimate of the modified measure.

Results: The combined value of RAEm is 3.19 with 95% confidence interval 1.67-6.13.

Conclusion: The excess relative risk of lung cancer from asbestos exposure is about three times higher in non-smokers than in smokers. The modified measure has been placed within a more versatile model of interaction. If interaction is present the relative risk from asbestos exposure changes only slightly between light and heavy smokers, but is higher in very light smokers and non-smokers. The relative risk estimated from epidemiological studies of a mixed population of non-smokers and smokers applies to smokers.
Commentary: the 1968 BOHS Chrysotile Asbestos Standard. T.L. Ogden, British Occupational Hygiene Society. 2003;47(1):3-6. Historical article PubMed · Publisher

Summary

This commentary, published for the British Occupational Hygiene Society's (BOHS) fiftieth anniversary, gave the author's personal view of the background and long-term significance of the Society's 1968 hygiene standard for chrysotile asbestos. The author reviewed earlier asbestos limits from the 1930s onward. He then described how the BOHS sub-committee judged a 1% risk of basal rales, an early sign of asbestosis, to be acceptable and related this sign to exposure in 290 men at Turner's Rochdale factory. The standard estimated the risk at <1% for about 100 fibre-yr/ml, equivalent to 2 fibres/ml over a 50-year working lifetime, and recommended sampling based on 3-month averages. The author summarized the criticisms: only current employees were studied, no disease progression was assumed after exposure ended, early dust levels were guessed, health effects were assessed by a single observer, and cancer was not taken into account. A 1983 BOHS committee put the probability of any of seven adverse effects at 17–20% at 100 fibre-yr/ml. The author traced how 2 fibres/ml spread worldwide, usually applied to single-shift samples. He described how inter-laboratory counting differences made its meaning unclear. He also described how the 1979 Advisory Committee on Asbestos moved away from deriving limits mainly from risk estimates. Britain's current 4 h chrysotile limit was 0.3 fibres/ml, and chrysotile use was prohibited with minor and temporary exceptions. The author concluded that the standard, with all its flaws, was a landmark.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration. E. Kauffer, P. Martin, M. Grzebyk, et al. 2003;47(5):413-26. PubMed · Publisher

Abstract

The use of direct-reading instruments to measure the airborne fibre number concentration is on the increase. The response of two of these instruments (FM-7400 and Fibrecheck FC-2) was compared with the conventional method of sampling on filters and counting by phase contrast microscopy. Four types of fibres were studied at different concentrations and relative humidity levels. The FM-7400 can be calibrated by the manufacturer for two different levels of sensitivity (standard and high). For the tests where it was set to the sensitivity level with which it had been calibrated, the ratio of the concentration measured by the instrument to the concentration obtained by the conventional method varied in the range 0.5-1 for the different types of fibres studied (chrysotile, glass wool and ceramic fibres). The Fibrecheck FC-2 is a much less versatile instrument. On the basis of a calibration allowing correct detection of asbestos fibres, it greatly overestimated the concentration of man-made mineral fibres. In its normal calibration state a fine chrysotile aerosol was poorly detected. For man-made mineral fibres, the response was highly dependent on the nature of the fibres. These instruments require calibration with the type of fibres to be studied. Unfortunately, this operation is not always accessible to the user and may require the services of a specialized laboratory, as the manufacturer is not always in a position to carry this out.
Exposure to brake dust and malignant mesothelioma: a study of 10 cases with mineral fiber analyses. K.J. Butnor, T.A. Sporn, V.L. Roggli. 2003;47(4):325-30. PubMed · Publisher

Abstract

Objectives: A large number of workers in the USA are exposed to chrysotile asbestos through brake repair, yet only a few cases of malignant mesothelioma (MM) have been described in this population. Epidemiologic and industrial hygiene studies have failed to demonstrate an increased risk of MM in brake workers. We present our experience of MM in individuals whose only known asbestos exposure was to brake dust and correlate these findings with lung asbestos fiber burdens.

Methods: Consultation files of one of the authors were reviewed for cases of MM in which brake dust was the only known asbestos exposure. Lung fiber analyses were performed using scanning electron microscopy (SEM) in all cases for which formalin-fixed or paraffin-embedded lung tissue was available.

Results: Ten cases of MM in brake dust-exposed individuals were males aged 51-73 yr. Nine cases arose in the pleura and one in the peritoneum. Although the median lung asbestos body count (19 AB/g) is at our upper limit of normal (range 0-20 AB/g), half of the cases had levels within our normal range. In every case with elevated asbestos fiber levels by SEM, excess commercial amphibole fibers were also detected. Elevated levels of chrysotile and non-commercial amphibole fibers were detected only in cases that also had increased commercial amphibole fibers.

Conclusions: Brake dust contains exceedingly low levels of respirable chrysotile, much of which consists of short fibers subject to rapid pulmonary clearance. Elevated lung levels of commercial amphiboles in some brake workers suggest that unrecognized exposure to these fibers plays a critical role in the development of MM.
Occupational characteristics of cases with asbestos-related diseases in The Netherlands. A. Burdorf, M. Dahhan, P. Swuste. 2003;47(6):485-92. PubMed · Publisher

Abstract

Objective: To describe the occupational background of cases with an asbestos-related disease and to present overall mesothelioma risks across industries with historical exposure to asbestos.

Methods: For the period 1990-2000, cases were collected from records held by two law firms. Information on jobs held, previous employers, activities performed and specific products used were obtained from patients themselves or next of kin. Branches of industry and occupations were coded and the likelihood of asbestos exposure was assessed. For each branch of industry, the overall risk of mesothelioma was calculated from the ratio of the observed number of mesothelioma cases and the cumulative population-at-risk in the period 1947-1960. In order to compare mesothelioma risks across different industries, risk ratios were calculated for the primary asbestos industry and asbestos user industries relative to all other branches of industry.

Results: In total, 710 mesotheliomas and 86 asbestosis cases were available. The average latency period was approximately 40 yr and the average duration of exposure was 22 yr. Ship building and maintenance contributed the largest number of cases (27%), followed by the construction industry (14%), the insulation industry (12%), and the navy and army, primarily related to ship building and maintenance (5%). In the insulation industry, the overall risk of mesothelioma was 5 out of 100 workers, and in the ship building industry, 1 out of 100 workers. The construction industry had an overall risk comparable with many other asbestos-using industries (7 per 10,000 workers), but due to its size claimed many mesothelioma cases.

Conclusion: The majority of cases with asbestos-related diseases had experienced their first asbestos exposure prior to 1960. For cases with first asbestos exposure after 1960, a shift was observed from the primary asbestos industry towards asbestos-using industries, such as construction, petroleum refining, and train building and maintenance. Due to the long latency period, asbestos exposure from 1960 to 1980 will cause a considerable number of mesothelioma cases in the next two decades.
Asbestos lung fibre analysis in the United Kingdom, 1976-96. G. Berry. 2002;46(6):523-6. PubMed · Publisher

Abstract

Objectives: To summarize data on changes in lung contents of asbestos types between 1976-77 and 1990-96 for mesotheliomas and controls in the UK.

Methods: Data were extracted from published studies of the years 1976, 1977 and 1990-96.

Results: Between 1976-77 and 1990-96 there was a large reduction in the amount of crocidolite in the lungs of both mesotheliomas and controls.

Conclusion: The results are consistent with the use of the different asbestos types in the UK, after taking into account the period of exposure and elimination of fibres from the lung in the time elapsed since exposure.
Developments in the RICE asbestos fibre counting scheme, 1992-2000. Regular Interlaboratory Counting Exchanges. P.W. Brown, A.D. Jones, B.G. Miller. 2002;46(3):329-39. PubMed · Publisher

Abstract

The UK's Regular Interlaboratory Counting Exchanges (RICE) scheme provides proficiency testing for laboratories counting asbestos fibres by phase contrast optical microscopy, as in the method for measurement of airborne fibre concentrations. From 1984 to 1992, the scheme used circulations of industrial samples containing mostly chrysotile, and reference values were obtained from fibre counts by automated image analysis. In 1992, lower density (< 100 fibres/mm2) samples from asbestos clearance operations were added and the new reference values were medians of the laboratories' determinations. In extensive data from 28 recent rounds of sample exchanges, the new reference values are shown to be more reliable than the old. Average counting levels have changed, with different trends according to fibre density. In low density samples, after initial increases, the levels appear to have stabilized. Counting levels on the higher density samples show a continuing trend of approximately 0.5% decrease per round. Widening the density range may have reduced the influence of counters' preconceptions of what values are expected and so their counts on the reference samples may now better reflect their routine counting. The implications of these findings and of other new developments, such as expected new counting rules, are discussed.
Performance of power assisted respirators during simulated asbestos removal. M.P. Clayton, A.E. Bailey, N.P. Vaughan, et al. 2002;46(1):49-59. PubMed · Publisher

Abstract

Protection factors were measured on full face mask power assisted respirators when worn by experienced asbestos removal operatives under simulated asbestos removal work conditions. The sulfur hexafluoride test method as defined in European Standards was employed to determine the leakage into the respirators. Protection factors were measured on a total of 21 test volunteers. The test method allowed protection factors to be related to wearer activities and practices. Poor fitting techniques and simulated reduction in the respirator's performance resulted in a reduction in the protection factor. Visual inspection of the RPE usually worn by the volunteers identified inadequate maintenance. This study re-emphasises that careful selection, facepiece fit testing and correct use and maintenance of RPE are essential to ensure optimum protection to the wearer.
The combination of effects on lung cancer of cigarette smoking and exposure in quebec chrysotile miners and millers. F.D. Liddell, B.G. Armstrong. 2002;46(1):5-13. PubMed · Publisher

Abstract

Although it is well known that both cigarette smoke and microscopic airborne asbestos fibres can cause lung cancer, evidence as to how these two agents combine is nebulous. Many workers have believed in the multiplicative theory, whereby asbestos increases the risk in proportion to the risk from other causes. However, evidence against this theory is mounting: a recent review concluded that the multiplicative hypothesis was untenable, and that the relative risk of lung cancer from asbestos exposure was about twice as high in non-smokers as in smokers, a finding largely independent of type of asbestos fibre. The criteria for entry to the current study were met by 7279 men in the 1891-1920 birth cohort of Quebec chrysotile miners and millers. The data consisted of date of birth, place of employment, smoking habit, asbestos exposure accumulated to age 55 and, for those 5527 who died between 1950 and June 1992, date and cause of death; 533 of the deaths were from lung cancer. For the principal analyses, ex-smokers were excluded from the study cohort, which comprised 5888 men, of whom 473 died of lung cancer. The conventional form of analysis is simply of the double dichotomy: non-smokers of cigarettes, 'unexposed' and exposed; all others, 'unexposed' and exposed. The respective standardized lung cancer mortality ratios (SMRs) were 0.29 and 0.62; and 1.37 and 1.72. Thus, the differences in relative risk, due to exposure, were closely similar, 0.33 and 0.35. On the other hand, the effects of asbestos measured by the corresponding ratios, 2.12 and 1.25, did differ, being 1.7 times as high in non-smokers as in others. The principal analysis was much more penetrating: the method was to fit models to a 'disaggregated' 6 x 10 array, by smoking habit (excluding ex-smokers) and asbestos exposure, of lung cancer SMRs. Both linear and log-linear models were fitted: the former included the additive and linear-multiplicative; the latter embraced the more conventional multiplicative form. The additive model fitted much the best. The fit of each multiplicative model was improved by the introduction of an interaction term that implied a less than multiplicative relationship. Thus smoking and exposure to chrysotile appear to have acted independently in causing lung cancer, with 10 cigarettes a day having an effect roughly equivalent to exposure amounting to 700 million particles per cubic foot x years. The refutation of the multiplicative hypothesis in these data reinforces its inapplicability in general; but the additive hypothesis is not generally applicable either. Indeed, there seems to be no good reason to believe that interactions conform to any simple theory. The implications are important.
The quantitative risks of mesothelioma and lung cancer in relation to asbestos exposure: the Wittenoom data. A. Rogers, G. Major. 2002;46(1):127-8; author reply 128-9. Comment · Letter PubMed · Publisher

Summary

In this letter, two occupational hygienists questioned the cumulative crocidolite exposure levels that Hodgson and Darnton (2000) used in their mesothelioma and lung cancer risk estimates for the Wittenoom cohort of about 6500 male Australian Blue Asbestos workers in Western Australia. The authors noted that the cohort worked at three mines and various mills over 23 years, all of which were always extremely dusty. They reported that most of the Mines' Inspectorate konimeter results from the early 1950s to 1966 were recorded as 1000+ particles per cc, indicating instrument overloading, and that these data were never suitable for estimating fibre concentrations. The only fibre monitoring was a 1966 survey by one author (G.M.) at the Colonial Gorge mine and mill. It covered 12 shifts and collected 38 static samples, and it was reported only in general terms in 1968. Others had derived median estimates of 50 fibres/ml for ever mill workers, 12 fibres/ml for ever mine but never mill workers and 5 fibres/ml for other work. The authors considered these somewhat low compared with 1966 dust levels. They concluded that there was insufficient information to calculate fibre dose scientifically, called the published values 'guesstimates', and denied that the original hygienist had verified them. In a reply, the cohort researchers acknowledged the inadequacy of the monitoring data, described the cohort follow-up, and stated that they never claimed Mr Major agreed with the estimates.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Tremolite and mesothelioma. V.L. Roggli, R.T. Vollmer, K.J. Butnor, et al. 2002;46(5):447-53. PubMed

Abstract

Background: Exposure to chrysotile dust has been associated with the development of mesothelioma and recent studies have implicated contaminating tremolite fibers as the likely etiological factor. Tremolite also contaminates talc, the most common non-asbestos mineral fiber in our control cases.

Methods: We examined 312 cases of mesothelioma for which fiber burden analyses of lung parenchyma had been performed by means of scanning electron microscopy to determine the content of tremolite, non-commercial amphiboles, talc and chrysotile. The vast majority of these patients were exposed to dust from products containing asbestos.

Results: Tremolite was identified in 166 of 312 cases (53%) and was increased above background levels in 81 cases (26%). Fibrous talc was identified in 193 cases (62%) and correlated strongly with the tremolite content (P < 0.0001). Chrysotile was identified in only 32 cases (10%), but still correlated strongly with the tremolite content (P < 0.0001). Talc levels explained less of the tremolite deviance for cases with an increased tremolite level than for cases with a normal range tremolite level (22 versus 42%). In 14 cases (4.5%) non-commercial amphibole fibers (tremolite, actinolite and/or anthophyllite) were the only fiber types found above background.

Conclusions: We conclude that tremolite in lung tissue samples from mesothelioma victims derives from both talc and chrysotile and that tremolite accounts for a considerable fraction of the excess fiber burden in end-users of asbestos products.
A proposal for harmonising laboratory performance assessment criteria in national asbestos fibre counting schemes. M.C. Arroyo, J.M. Rojo. 2001;45(6):447-55. PubMed · Publisher

Abstract

Four European national asbestos fibre counting proficiency testing schemes have been studied in order to compare their criteria for the assessment of laboratory performance. Performance assessment is based on each laboratory's results after counting a certain number of samples. Two methods are currently being applied. To be classified 'satisfactory' laboratories must obtain at least 75% of normalised counts lying within defined performance limits (in three schemes), or the median and coefficient of variation of normalised counts must be within performance limits (in the fourth scheme). Differences in the numbers of test samples mean that the schemes are operating with different selectivity in assessing their laboratories' performances. Differences in the percentage of laboratory results falling within performance limits indicate that the schemes do not operate the same confidence probability in correctly assessing individual counts. It means that some schemes may be more lenient than others. This paper discusses two proposals to move towards harmonisation of the asbestos fibre counting proficiency testing schemes: (i) standardisation of the number of samples used for laboratory assessment and (ii) changes to the criteria to establish the limits of satisfactory performance.
Performance of asbestos fibre counting laboratories by transmission electron microscopy. B. Préat. 2001;45(6):500-1. Comment · Letter PubMed · Publisher
Confusion about the precision of asbestos fibres counting by electron microscopy. B. Préat. 2000;44(1):75-6. Letter PubMed · Publisher

1990s

1998 and beyond--Legge's legacy to modern occupational health. J.M. Harrington. 1999;43(1):1-6. Historical article PubMed · Publisher

Abstract

Thomas Legge achieved much in his professional lifetime. The purpose of this lecture is to highlight some of these achievements in the light of what we have achieved since then. In other words, if Legge was in the audience today, how would he feel we have performed? On 'industrial maladies', progress has been made in reducing poisoning by heavy metals but our success with chrome ulceration and lead depends on surveillance and control. Room for improvements remain. For asbestos related diseases, Legge would be disappointed with our progress. Two areas of particular concern to Legge were upper limb disorders and 'occupational neurosis'. Much remains to be done. As a member of the 1st Committee on Compensatable Diseases, a review of the Scheme to date will focus on the common diseases now being prescribed and on the threats to the Scheme from the Benefits review. For the future, there are many challenges in the newer workplaces and the changing workforces. The HSE initiatives for a new occupational strategy and the Government Green Paper on Public Health provide great opportunities for the occupational health professional to influence the nature and shape of future public health strategy. Above all we must have some of Legge's characteristics to achieve this-vision, passion and commitment.
Minimising health hazards associated with derogated products and in-situ materials containing chrysotile contaminated with amphibole asbestos fibres. R.M. Howie. 1999;43(7):493-8. Letter PubMed · Publisher
A comparison of historic asbestos measurements using a thermal precipitator with the membrane filter-phase contrast microscopy method. G. Burdett. 1998;42(1):21-31. PubMed · Publisher

Abstract

The published results and analytical methods used in a 1938 survey of the spinning area in a UK crocidolite asbestos factory have been described and re-interpreted, by comparing the method used with the current membrane filter-phase contrast microscopy (MF-PCM) method for asbestos. By good fortune, most of the original microscope, and thermal precipitator sampling heads similar to those used for sampling were available, as well as guidance from the factory inspector who collected and analysed the original samples. A textile grade crocidolite asbestos was used to generate a fibrous dust cloud whose size distribution was characterised by scanning and transmission electron microscopy and found to give a close approximation to the fibre size distributions monitored in 1938. Samples taken over the same sampling time, but at lower concentrations than originally sampled, showed that the thermal precipitator-oil immersion microscopy (TP-OI) method used at x 2000 magnification, gave higher > 5 microns long fibre counts by a factor of between 3 and 4, than the current MF-PCM method. The differences in performance could be explained by the superior resolving power of the TP-OI method for fine crocidolite fibres. Exposures of airborne asbestos fibres in the spinning area were found to be equivalent to about 20 f ml-1 for personal samples and 10 f ml-1 for area samples, but due to the high levels of ventilation on the day the samples were collected, the average levels throughout the year may have been somewhat higher.
Does risk perception affect behaviour and exposure? A pilot study amongst asbestos workers. A.J. Stewart-Taylor, J.W. Cherrie. 1998;42(8):565-9. PubMed · Publisher

Abstract

It is hypothesised that there is a causal association between workers' perceptions of the risks from handling hazardous materials, their behaviour while working and their consequent exposure. This has been investigated in a small group of workers carrying out remedial work on amosite insulating boards and similar products. Risk perception was first assessed using a questionnaire and then the workers' behaviour was recorded alongside task-based measurements of fibre exposure. There was a clear association of higher cumulative exposures when workers used power tools compared to manual methods (about seven times higher). Careful bagging was shown to reduce exposures by a smaller margin, (approximately half). Workers whose perception of the risks was poorer were found to be more likely to use power tools to remove the asbestos containing material. However, fibre exposure was not found to be directly associated with risk perception. Further work is necessary to clarify the validity of the original hypothesis.
Dust exposure and lung cancer in Quebec chrysotile miners and millers. F.D. Liddell, A.D. McDonald, J.C. McDonald. 1998;42(1):7-20. PubMed · Publisher

Abstract

A large cohort of men born between 1891 and 1920 and employed for at least a month in the chrysotile producing industry of Quebec has been under study since 1966. These men were followed from first employment (the earliest in 1904) to 1992, by which time over 8000 had died, 657 from lung cancer. The current study is of 488 cases of lung cancer formerly employed at three places, viz. a major complex, here called Company 3, in the region of Thetford Mines (243 cases), the mine and mill in the town of Asbestos (206) and a small asbestos-products factory in the same town (39). For each case, four referents were sought by random selection from among survivors to a greater age, after matching on place of employment, age of starting work, smoking habit and date of birth. This process was highly successful, although six cases had less than four referents. For each man (the 488 cases with 1941 referents) and for each calendar year of employment, we obtained the fraction of the year worked at various levels of intensity, assessed in 13 'dust categories' of mpcf (million particles per cubic foot). We then calculated how many years each man spent at these various levels; these years, adjusted for the length of the working week (66 h until 1937; 48 h 1938-1949; and 40 h 1950-1985), were accumulated up to ten years before the death of the case. The men were classified according as they were non- or ex-smokers, or smokers, of cigarettes. For each man at Company 3 and one referent for each, his years of work in a central area of five mines and in a peripheral area of ten mines were differentiated; contamination of the chrysotile by fibrous tremolite was known to be much greater in the central than in the peripheral area. Case-referent comparisons, within place of employment, were made by conditional logistic regression. As anticipated from earlier subject-years analyses, lung cancer risks were found to be negligible for years worked in dust categories 1 and 2 (averaging 0.5 and 2 mpcf), regardless of place; as the upper limit of category 1 is considerably higher than permitted nowadays, the lung cancer risk from exposure to chrysotile at permitted levels can be taken as extremely small. Patterns of exposure-response for higher categories were irregular. At Company 3, some risks appeared elevated for years spent in the higher dust categories: 3-4, 5-7, 8-10 and 11-13, with averages around 9, 20, 36 and 92 mpcf, respectively. For categories 3-4 and 8-10, the odds ratios were high for some or all work in the central area, but minimal for years spent in the peripheral area only. Odds ratios were fairly low for cigarette smokers who worked in categories 5-7 and also for years spent in the highest categories (11-13). At the mine and mill in Asbestos, all risks were low except for years worked by non- and ex-smokers in categories 7-13 (ca. 40 mpcf). There were no increased risks at the factory. It was known from the subject-years analyses that most of the excess had occurred at Company 3, but it is now clear that for all practical purposes it was confined to the central area there, probably due largely to fibrous tremolite and in dust conditions of at least dust category 3. The average of this category was 7 mpcf or very roughly 24 fibres/ml, about two orders of magnitude higher than today's hygiene standards.
Respirable fibres: surfactant coated fibres release more Fe3+ than native fibres at both pH 4.5 and 7.2. C.E. Fisher, D.M. Brown, J. Shaw, et al. 1998;42(5):337-45. PubMed · Publisher

Abstract

Exposure to asbestos is associated with several lung diseases. The carcinogenic action of asbestos is not fully understood but oxidative stress is considered to play a role. Iron on the surface can lead to Fenton chemistry and the Haber Weiss reaction producing free radicals such as the hydroxyl radical, which is likely to be important. Little is known of the pathogenic action of man-made fibres. This study involved the use of a panel of man-made fibres, some of which were shown to be pathogenic and others shown to be non-pathogenic in recent animal studies. A short term assay measuring Fe3+ release from the fibres over a 20 hour time period, and also a longer study of 12 week, found that pathogenic and non-pathogenic fibres could not be differentiated according to Fe3+ release only. Iron release from native fibres was compared with that from surfactant-coated fibres, and in all cases surfactant coated fibres released more Fe3+ inferring that in vivo lung lining fluid coats native fibres and therefore affects the fibre surface chemistry and hence reactivity.
Unfinished business: the asbestos textiles mystery. J.C. McDonald. 1998;42(1):3-5. Editorial · Review PubMed · Publisher

Summary

In this invited editorial, the author reviewed evidence on why lung cancer risks among asbestos textile workers were much higher than expected from chrysotile exposure in other industries. He described two 1983 cohort studies of a textile plant in Charleston, South Carolina, of 1261 white males and of 2545 men. Using over 5000 impinger samples, both found closely similar linear exposure-response relationships for lung cancer (RR = 1 + 0.069 and 1 + 0.051 per mpcf.y). The plant used almost only chrysotile. Similar lung cancer findings came from a plant in Pennsylvania and a factory in Rochdale. The textile exposure-response slope was some 50 times steeper than in Quebec chrysotile miners and millers. Mesothelioma rates at Charleston (about 2 per 1000 deaths) were in line with Quebec. Possible explanations included exposure estimation errors, fibre size differences, smoking and mineral oil sprays; apart possibly from the oils, none seemed capable of reducing the difference below 10-fold. One lung burden study (161 samples) found similar fibre size distributions in Charleston and Thetford Mines except for tremolite fibres over 20 µm. Another (54 cohort members, 34 referents) found higher chrysotile and tremolite concentrations in workers. The author concluded that the remaining hypotheses, fibre length and mineral oil spray, were not well supported. He said the question remained unsolved after 15 years and needed far greater contributions from physical scientists and experimental toxicologists.

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A comparative study of the clearance of respirable para-aramid, chrysotile and glass fibres from rat lungs. A. Searl. 1997;41(2):217-33. PubMed · Publisher

Abstract

A number of studies have indicated that the relative toxicity of different fibre types after inhalation is related to their durability within lung tissue. The aim of this study was to assess the relative biopersistence of respirable para-aramid fibrils, chrysotile asbestos and code 100/475 glass fibres in rat lungs. The biopersistence of all three test fibres was measured by quantifying the changes in retained lung burden through time following 10 days inhalation exposure to the same target concentration (700 fibres ml-1) for each fibre type. The lung burden analyses for all three fibre types show large reductions in number and volume of retained fibres during the 16 months following exposure. Most of this reduction in lung fibre burden occurred during the first 3 months following exposure but the pattern of clearance of different size classes varies with fibre type. The para-aramid data show rapid clearance of the longest fibrils during the first months following exposure, combined with an initial increase in the numbers of shorter fibrils. This is consistent with the disintegration of para-aramid fibrils into shorter fragments that subsequently are more readily cleared by macrophages. The code 100/475 glass fibre data also show rapid clearance of the longer fibres combined with an increase in the numbers of very short fibres, consistent with the removal of long fibres through disintegration. In contrast, the chrysotile data show a more rapid reduction in the numbers of retained short fibres than of long fibres, which is consistent with preferential clearance of short fibres by macrophages and minimal transverse breakage of fibres. The biopersistence of all three fibre types, in terms of overall percentage of fibres retained after 16 months is similar, but the durability of long (> 15 microns) chrysotile fibres is very much greater than that of long fibres of code 100/475 glass or para-aramid. The clearance of the three fibre types cannot be adequately described by the first order kinetic model that is often applied in studies of lung clearance. The apparent half time of clearance of each of the fibre types depends on the size fraction and time interval examined.
Acid leaching studies of chrysotile asbestos from mines in the Coalinga region of California and from Quebec and British Columbia. A. Morgan. 1997;41(3):249-68. PubMed · Publisher

Abstract

The dissolution of magnesium (Mg) and silicon (Si) from various samples of chrysotile asbestos was measured in N HCl at 25 degrees C. Nine samples were used, five from Canada and four from the Coalinga deposit in California. With milled samples from Quebec, the fraction of Mg dissolving was linearly related to the square root of the leaching time until at least 65% had dissolved. With a hand-picked sample of ore from Quebec, the sample from British Columbia and all the Californian samples, the Mg leaching patterns were sigmoid. The leaching patterns for Si were sigmoid in shape for all the materials tested. Mean Mg dissolution rates were calculated for each leaching period. Considerable differences were observed between samples from the different mining regions and also between hand-picked and milled samples from the same mine. Initially, Mg dissolved more rapidly from milled Quebec chrysotiles than from the Coalinga samples. This difference is due in part to the rapid dissolution of non-structural brucite, present in all the samples from Quebec but not in those from California. An additional cause is greater damage to the fibre surfaces resulting from the milling to which the less readily-opened fibres, typical of the Quebec mining area, were subjected. Once this readily-available Mg had dissolved, there was little difference in leaching rates between milled and unmilled samples from the different regions. When the fraction of Mg dissolving is plotted against that of Si, all the materials follow a similar pattern, suggesting that the dissolution of Si (as silica) is the rate-controlling step in the dissolution of Mg.
Acid leaching studies of neutron-irradiated chyrsotile asbestos. A. Morgan, R.J. Talbot. 1997;41(3):269-79. PubMed · Publisher

Abstract

Samples of chrysotile from Quebec (UICC B and Jeffrey 4T-30) and from the Coalinga region of California (Calidria RG-144) were irradiated with thermal neutrons in a reactor. The main activation products induced were 46Sc, 51Cr, 59Fe and 60Co. Accurately weighed samples of the irradiated materials were dispersed in N HCl by hand shaking for 10 s. After leaching for predetermined periods at 25 degrees C, the samples were filtered and the concentrations of Mg determined in the filtrates by inductively-coupled plasma atomic emission spectrometry (IPC-AES) and the activities of the four radionuclides by high resolution gamma-ray spectrometry. Similar measurements were made on solutions obtained by refluxing samples of irradiated chrysotile with 2N HCl for 2 h. The specific activities of each of the four activation products were calculated in arbitrary units and, as the concentrations of Sc, Cr, Fe and Co in the UICC B sample had already been determined, it was possible to estimate the concentrations of these elements in the other two samples. Similarities in the leaching patterns of magnesium and of the activation products showed that with all samples, high proportions of the parent trace elements were present in the form of isomorphous substitutes for magnesium in structural brucite. Agreement was closest with the Calidria chrysotile in which all the radionuclides had a similar pattern. With the Jeffrey and UICC B samples, the presence of a high proportion of the iron as relatively insoluble magnetite accounted for the observed discrepancy in behaviour between 59Fe and Mg. More detailed calculation of leaching rates over specific time intervals showed that, initially, 51Cr and 60Co dissolved more rapidly than Mg but that this was followed by a period in which the opposite was the case. It was concluded that the Calidria RG-144 sample is an ideal candidate for studies of magnesium dissolution in vivo.
Chrysotile, tremolite and carcinogenicity. J.C. McDonald, A.D. McDonald. 1997;41(6):699-705. PubMed · Publisher

Abstract

It has been suspected for many years that amphibole fibres in the tremolite series, a low level contaminant of chrysotile asbestos, may contribute disproportionately to the incidence of mesothelioma and perhaps other exposure-related cancers. A cohort of some 11,000 Quebec chrysotile workers, 80% of whom have now died, provided the opportunity to examine this hypothesis further. An analysis was made of deaths from mesothelioma (21), cancers of the lung (262), larynx (15), stomach (99), and colon and rectum (76), in men employed by the largest company in Thetford Mines, with closely matched referents. Risks were estimated by logistic regression for these five cancers in two groups of mines--five mines located centrally and ten mines located peripherally; tremolite contamination had been demonstrated to be some four times higher in the former than in the latter. Odds ratios for work in the central mines were raised substantially and significantly for mesothelioma and lung cancer, but not for the gastric, intestinal or laryngeal cancer sites. In the peripheral mines, there was little or no evidence of increased risk for any of the five cancers. The hypothesis that, because of the difference in distribution of fibrous tremolite, cancer risks in the central area would be greater than in the periphery was thus substantiated. That the explanation may lie in the greater biopersistence of amphibole fibres than chrysotile is important in framing policies for the use and control of asbestos and is directly relevant to the selection of man-made mineral fibre substitutes.
Comparison of cytotoxicity of man-made vitreous fibres. K. Luoto, M. Holopainen, M. Sarataho, et al. 1997;41(1):37-50. PubMed · Publisher

Abstract

The purpose of the study was to compare the cytotoxicity of man-made vitreous fibres (MMVFs): four refractory ceramic fibres (RCFs 1-4), two glasswool fibres (MMVF 10 and 11), a rockwool fibre (MMVF 21) and a slagwool fibre (MMVF 22). The ability of the fibres to induce haemolysis in sheep erythrocytes, to release lactate dehydrogenase (LDH) from rat alveolar macrophages (AM) and to increase the production of reactive oxygen metabolites (ROMs) in human polymorphonuclear leukocytes (PML) was studied. To assess the relative cytotoxicity of MMVFs, their toxicity was compared with that induced by quartz, chrysotile or titanium dioxide. MMVFs induced a modest, but dose-dependent, increase of haemolysis at doses of 0.5, 2.5 and 5.0 mg ml-1. The amount of haemolysis and LDH release induced by MMVFs was generally similar to that induced by titanium dioxide. Glasswool fibre MMVF 10 induced less LDH release from rat AM than rockwool MMVF 21 or slagwool MMVF 22 fibres, whereas glasswool fibre MMVF 11 induced less LDH release than slagwool fibre MMVF 22 (P < 0.05). All fibres also dose-dependently increased the production of ROMs at doses between 25 and 500 micrograms ml-1. The shapes of the time-courses of MMVF-induced production of ROMs suggest that the mechanisms whereby the different fibres induce ROM production may exhibit similar features. There are clear-cut differences in the potency of various MMVFs to induce cytotoxicity and oxidative burst. The present results also emphasize the importance of using several measures of toxicity when assessing the biological activity of various fibres in vitro.
Magic, menace, myth and malice. F.D. Liddell. 1997;41(1):3-12. Comment · Editorial · Historical article PubMed · Publisher

Abstract

In the 1950s, asbestos had so many uses that it was known as the magic mineral. However, in the next few years it was established that severe exposure to respirable asbestos fibres had led to respiratory fibrosis, or asbestosis, excess lung cancer, and mesothelioma. Ignoring the word 'severe' in the preceding sentence, an anti-asbestos lobby, based in the Mount Sinai School of Medicine of the City University of New York, promoted the fiction that asbestos was an all-pervading menace, and trumped up a number of asbestos myths for widespread dissemination, through media eager for bad news. These included: all workers ever exposed to asbestos will die prematurely of asbestos-related disease; all forms of asbestos are equally hazardous; one asbestos fibre can kill; any substitute for asbestos must be less harmful. Like all myths, they were inventions without foundation and entirely untrue, but they were welcomed by the media and promulgated so ardently that they were soon almost universally believed, engendering widespread 'fibre-phobia'; the anti-asbestos lobby (hereinafter The Lobby) became both influential and powerful. When the first findings from Quebec were published they threatened to dispel the myths, and so The Lobby tried to denigrate them. As this could not be done on scientific grounds, a campaign of intense malice was conducted against the principal Quebec investigator. And of course any group, such as that at Tulane University in New Orleans, which found evidence contrary to the myths was also castigated or even ostracised. Nevertheless, honest scientists have continued their endeavours, and what follows provides some background to the study that is reported in the accompanying paper (p. 13).

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Mesothelioma in Quebec chrysotile miners and millers: epidemiology and aetiology. A.D. McDonald, B.W. Case, A. Churg, et al. 1997;41(6):707-19. PubMed · Publisher

Abstract

In a cohort of some 11,000 men born 1891-1920 and employed in the Quebec chrysotile production industry, including a small asbestos products factory, of 9780 men who survived into 1936, 8009 are known to have died before 1993, 38 probably from mesothelioma--33 in miners and millers and five in factory workers. Among the 5041 miners and millers at Thetford Mines, there had been 4125 deaths from all causes, including 25 (0.61%) from mesothelioma, a rate of 33.7 per 100,000 subject-years; the corresponding figures for the 4031 men at Asbestos were eight out of 3331 (0.24%, or 13.2 per 100,000 subject-years). At the factory in Asbestos, where all 708 employees were potentially exposed to crocidolite and/or amosite, there were 553 deaths, of which five (0.90%) were due to mesothelioma; the rate of 46.2 per 100,000 subject-years was 3.5 times higher than among the local miners and millers. Six of the 33 cases in miners and millers were in men employed from 2 to 5 years and who might have been exposed to asbestos elsewhere; otherwise, the 22 cases at Thetford were in men employed 20 years or more and the five at Asbestos for at least 30 years. The cases at Thetford were more common in miners than in millers, whereas those at. Asbestos were all in millers. Within Thetford Mines, case-referent analyses showed a substantially increased risk associated with years of employment in a circumscribed group of five mines (Area A), but not in a peripherally distributed group of ten mines (Area B); nor was the risk related to years employed at Asbestos, either at the mine and mill or at the factory. There was no indication that risks were affected by the level of dust exposure. A similar pattern in the prevalence of pleural calcification had been observed at Thetford Mines in the 1970s. These geographical differences, both within the Thetford region and between it and Asbestos, suggest that the explanation is mineralogical. Lung tissue analyses showed that the concentration of tremolite fibres was much higher in Area A than in Area B, a finding compatible with geological knowledge of the region. These findings, probably related to the far greater biopersistence of amphibole fibres than chrysotile, have important implications in the control of asbestos related disease and for wider aspects of fibre toxicology.
The 1891-1920 birth cohort of Quebec chrysotile miners and millers: development from 1904 and mortality to 1992. F.D. Liddell, A.D. McDonald, J.C. McDonald. 1997;41(1):13-36. PubMed · Publisher

Abstract

This paper draws together the mortality experience for a cohort of some 11000 male Quebec Chrysotile miners and millers, reported at intervals since 1971 and now again updated. Of the 10918 men in the complete cohort, 1138 were lost to view, almost all never traced after employment of only a month or two before 1935; the other 9780 men were traced into 1992. Of these, 8009 (82%) are known to have died: 657 from lung cancer, 38 from mesotheliona, 1205 from other malignant disease, 108 from pneumoconiosis and 561 from other non-malignant respiratory diseases (excluding tuberculosis). After early fluctuations. SMRs (all causes) against Quebec rates have been reasonably steady since about 1945. For men first employed in Asbestos, mine or factory, they were very much what might have been expected for a blue collar population without any hazardous exposure. SMRs in the Thetford Mines area were almost 8% higher, but in line with anecdotal evidence concerning socio-economic status. At exposures below 300 (million particles per cubic foot) x years, (mpcf.y), equivalent to roughly 1000 (fibres/ml) x years-or, say, 10 years in the 1940s at 80 (fibres/ml)-findings were as follows. There were no discernible associations of degree of exposure and SMRs, whether for all causes of death or for all the specific cancer sites examined. The average SMRs were 1.07 (all causes), and 1.16, 0.93, 1.03 and 1.21, respectively, for gastric, other abdominal, laryngeal and lung cancer. Men whose exposures were less then 300 mpcf.y suffered almost one-half of the 146 deaths from pneumoconiosis or mesothelioma; the elimination of these two causes would have reduced these men's SMR (all causes) from 1.07 to approximately 1.06. Thus it is concluded from the viewpoint of mortality that exposure in this industry to less than 300 mpcf.y has been essentially innocuous, although there was a small risk or pneumoconiosis or mesothelioma. Higher exposures have, however, led to excesses, increasing with degree of exposure, of mortality from all causes, and from lung cancer and stomach cancer, but such exposures, of at least 300 mpcf.y, are several orders of magnitude more severe than any that have been seen for many years. The effects of cigarette smoking were much more deleterious than those of dust exposure, not only for lung cancer (the SMR for smokers of 20+ cigarettes a day being 4.6 times higher than that for non-smokers), but also for stomach cancer (2.0 times higher), laryngeal cancer (2.9 times higher), and-most importantly-for all causes (1.6 times higher).
A study of personal and area airborne asbestos concentrations during asbestos abatement: a statistical evaluation of fibre concentration data. J.H. Lange, P.R. Lange, T.K. Reinhard, et al. 1996;40(4):449-66. PubMed · Publisher

Abstract

Data were collected and analysed on airborne concentrations of asbestos generated by abatement of different asbestos-containing materials using various removal practices. Airborne concentrations of asbestos are dramatically variable among the types of asbestos-containing material being abated. Abatement practices evaluated in this study were removal of boiler/pipe insulation in a crawl space, ceiling tile, transite, floor tile/mastic with traditional methods, and mastic removal with a high-efficiency particulate air filter blast track (shot-blast) machine. In general, abatement of boiler and pipe insulation produces the highest airborne fibre levels, while abatement of floor tile and mastic was observed to be the lowest. A comparison of matched personal and area samples was not significantly different, and exhibited a good correlation using regression analysis. After adjusting data for outliers, personal sample fibre concentrations were greater than area sample fibre concentrations. Statistical analysis and sample distribution of airborne asbestos concentrations appear to be best represented in a logarithmic form. Area sample fibre concentrations were shown in this study to have a larger variability than personal measurements. Evaluation of outliers in fibre concentration data and the ability of these values to skew sample populations is presented. The use of personal and area samples in determining exposure, selecting personal protective equipment and its historical relevance as related to future abatement projects is discussed.
Exposure to asbestos fibres during gasket removal. S.K. Spence, P.S. Rocchi. 1996;40(5):583-8. PubMed · Publisher

Abstract

In the chemical industry, asbestos gaskets have been used extensively to prevent leakage between solid surfaces. The purpose of this study was to assess the potential personal exposure to asbestos fibres during gasket removal and thus to determine what is reasonably required in terms of protective regime and work method. Two groups were studied: group A, who only removed gaskets if they could be removed easily and without breaking; and group B, who removed gaskets which were left by the first group. For both groups, the gasket was first made wet before removal. The samples were analysed using phase-contrast microscopy and transmission electron microscopy. The average exposure to fibres for group A, averaged over the work period, was 0.04-0.242 fibres ml-1 as determined by phase-contrast microscopy. On further analysis with transmission electron microscopy it was found that only four of the 11 samples contained asbestos in very low concentrations and that most of the fibres, which were identified using phase-contrast microscopy, probably originated from the glass fibre lagging around the pipes. For group B the average fibre concentration, averaged over the work period, as determined by phase-contrast microscopy, ranged between below the detection limit and 0.02 fibres ml-1. The subsequent transmission electron microscopy analysis shows that the exposure to asbestos fibres ranged between below the limit of detection to 0.004 fibres ml-1. This study shows that the exposure to asbestos fibres during gasket removal activities was well within the 8-h average exposure limit of 0.3 fibres ml-1.
The use of a new static device based on the collection of the thoracic fraction for the assessment of the airborne concentration of asbestos fibres by transmission electron microscopy. E. Kauffer, J.C. Vigneron, Fabriès, et al. 1996;40(3):311-9. PubMed · Publisher

Abstract

A new static device, the CATHIA sampling head, based on the collection of the thoracic fraction is proposed for the assessment of the airborne concentration of asbestos fibres by transmission electron microscopy. By comparison with a standard aerosol sampling head, it has been shown that this sampler reduces the total mass concentration, but does not introduce any change in the most common index used to characterize an asbestos aerosol fibre, that is the concentration of fibres with length greater than 5 microns, diameter less than 3 microns and length to diameter ratio greater than 3. The homogeneity of the deposited dust on the collection filter favours the use of this sampling head with both the indirect and direct preparation methods.
A review of inhalation toxicology studies with para-aramid fibrils. D.B. Warheit. 1995;39(5):691-7. Review PubMed · Publisher

Abstract

The paper summarizes the results of inhalation toxicology studies associated with para-aramid (p-aramid) fibrils. The review is subdivided into two categories: the results of inhalation toxicity studies and mechanistic inhalation studies. Keratin-associated lesions were observed in the lungs of female rats following chronic exposure to high concentrations of p-aramid. These lesions were originally interpreted as cystic keratinizing squamous cell carcinomas (CKSCC). In recent years, this keratinizing lesion has been observed in the lungs of rats with greater regularity in numerous chronic inhalation studies following exposures to a variety of dusts. In an attempt to reach a consensus on an appropriate diagnosis for this lesion, an international panel of pathologists was convened to evaluate the morphological aspects of this lesion. The panel considered that the most appropriate diagnosis for this lesion was 'proliferative keratin cyst' (PKC), the biological potential of the PKC remains controversial, but it appears to be unique to the rat species and has little relevance for humans. Mechanistic studies with p-aramid have demonstrated that acute inhalation of high concentrations of fibrils produces a potent but transient pulmonary inflammatory and cell labelling response. The inhaled fibrils have low durability in the lungs of rats as evidenced by a progressive decrease in median fibre lengths with increasing residence time in the lung. In contrast, in a comparative study, size-separated chrysotile asbestos produced a sustained increase over controls in cellular proliferation responses of terminal airways, parenchyma, subpleural and mesothelial regions.(ABSTRACT TRUNCATED AT 250 WORDS)
An index of past asbestos exposure as applied to car and bus mechanics. N. Plato, G. Tornling, C. Hogstedt, et al. 1995;39(4):441-54. PubMed · Publisher

Abstract

Different ways to describe historic fibre exposure from asbestos-containing friction materials were studied and compared for a group of 103 car and bus mechanics with more than 20 years employment and 15 years of asbestos exposure. A model was constructed to calculate cumulative asbestos exposure from friction materials including duration, intensity and exposure last year. The model is a combination of an additive and a multiplicative model, where an asbestos index was constructed that takes both near field and far field exposure into consideration. The model was based upon data from the international literature and quantitative asbestos measurements performed 1976-1988 in Swedish car repair workshops. The fibres were counted by phase-contrast microscopy with fibre criteria of length > 5 microns and aspect ratio > or = 3:1. The mechanics' fibre exposure at 398 repair workshops during a period of 48 years were calculated using the model. The mean cumulative exposure was estimated to be 2.6 f ml-1 * year. The annual cumulative exposure was highest for truck mechanics in the early 1960s. The car mechanics had a time-weighted average fibre exposure range of 0.11-0.41 f ml-1 (mean 0.21 f ml-1) in 1965 compared to 0.003-0.08 f ml-1 (mean 0.021 f ml-1) in 1985. In order to validate the model, the mechanic's fibre exposure estimated using the model were compared with representative asbestos exposure measurements for car mechanics during the 1960s and the 1970s (correlation coefficient = 0.69). Five lung physiological variables (FVC, TLC, FEV1, TLco and CV%) were used to study exposure-response relationships. None of the exposure parameters suggested any significant relationship between exposure and decrease in lung function.
Assessment of the toxicity of man-made fibres. A final report of a workshop held in Paris, France 3-4 February 1994. J. Bignon, P. Brochard, R. Brown, et al. 1995;39(1):89-106. Review PubMed · Publisher
Summary

This report summarized a workshop held in Paris, France, on 3-4 February 1994. The workshop examined experimental methods for identifying man-made fibres (MMFs) that pose a significant carcinogenic risk to humans. More than 130 scientists, government officials and industry representatives attended. It covered three themes: a priori risk criteria, detection and screening assays, and inhalation tests. Nineteen scientists presented papers. Rapporteurs summarized the papers and discussions, and all participants reviewed the summaries paragraph by paragraph. The meeting aimed to record agreement where it existed rather than to reach consensus.

Presenters reported the following:
- In vitro dissolution rates could predict the dissolution of long (>20 µm) fibres in rat lungs.
- Long glass fibres were cleared faster than short ones.
- In rat inhalation studies, chrysotile and crocidolite asbestos and refractory ceramic fibre (RCF 1) produced fibrosis, lung tumours and mesothelioma. RCF produced a 42% mesothelioma incidence in hamsters.
- Glass wool and slag wool did not significantly increase lung tumours. Rock wool caused minimal fibrosis.
- Participants disagreed about the value of intraperitoneal injection tests.
- One presenter estimated that humans had a tumour risk from asbestos at fibre concentrations 300 times lower than those needed in rats. He concluded that rat inhalation studies were not sensitive enough to detect hazard and risk in humans exposed to asbestos.
The workshop generally agreed that properly designed long-term inhalation studies were relevant to assessing MMF hazard. It did not fully agree on their sensitivity or on the need for a second species. Recommendations included:
- standardized tests and interlaboratory comparisons;
- reference asbestos and erionite fibres;
- a multi-dose asbestos inhalation study to compare rats and humans;
- studies of fibre burden in human lungs.
PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Chronic inhalation studies of man-made vitreous fibres: characterization of fibres in the exposure aerosol and lungs. T.W. Hesterberg, W.C. Miiller, P. Thevenaz, et al. 1995;39(5):637-53. PubMed · Publisher

Abstract

Inhalation studies were conducted to determine the chronic biological effects in rodents of respirable fractions of different man-made vitreous fibres (MMVFs), including refractory ceramic fibre (RCF), fibrous glass, rock (stone) wool and slag wool. Animals were exposed nose-only, 6 h per day, 5 days per week, for 18 months (hamsters) or 24 months (rats). Exposure to 10 mg m-3 of crocidolite or chrysotile asbestos induced pulmonary fibrosis, lung tumours and mesothelioma in rats, thus validating the inhalation model with known human carcinogenic fibres. Exposure of rats to 30 mg m-3 of refractory ceramic fibres (RCF) also resulted in pulmonary fibrosis as well as significant increases in lung tumours and mesothelioma. In hamsters, 30 mg m-3 of RCF induced a 41% incidence of mesotheliomas. Exposure of rats to 30 mg m-3 of fibre glasses (MMVF 10 or 11) or of slag wool (MMVF 22) was associated with an inflammatory response, but no mesotheliomas or significant increase in the lung tumours were observed. Rock wool (stone wool: MMVF 21) at the same exposure level resulted in minimal lung fibrosis, but no mesotheliomas or significant increase in the lung tumours were observed. Fibre numbers (WHO fibres) and dimensions in the aerosols and lungs of exposed animals were comparable in this series of inhalation studies. Differences in lung fibre burdens and lung clearance rates could not explain the differences observed in the toxicologic effects of the MMVFs. These findings indicate that dose, dimension and durability may not be the only determinants of fibre toxicity. Chemical composition and the surface physico-chemical properties of the fibres may also play an important role.
Deposition of inhaled asbestos and man-made mineral fibres in the respiratory tract. A. Morgan. 1995;39(5):747-58. Review PubMed · Publisher

Abstract

This paper reviews publications dealing with the deposition of fibrous particles, including asbestos and man-made mineral fibres, in the respiratory tract of man and experimental animals, particularly of the rat. The effects of fibre diameter and length on total, thoracic and alveolar deposition are discussed. Total deposition in the respiratory tract of the rat increases quite steeply with aerodynamic diameter (Dae) from about 20% at a Dae of 1 micron to 100% at a Dae of 5 microns. Deposition in the alveolar region reaches a peak of about 10% at a Dae of about 2 microns, which corresponds to an actual fibre diameter of about 0.4 microns. For fibres with diameters greater than this, alveolar deposition falls rapidly. For example, long glass fibres with an actual diameter of 1.5 microns or short glass fibres with an actual diameter of 3 microns are essentially non-respirable in the rat. The fate of fibres deposited in different regions of the respiratory tract of the rat is also discussed and the factors which predispose fibres either to remain in alveolar macrophages or to be transferred to the interstitium and pulmonary lymphatics. Finally, the distributions in the lungs of fibres administered by inhalation and by intratracheal instillation are compared, and the advantages and drawbacks of each method of delivery discussed.
Detection of mineral fibre carcinogenicity with the intraperitoneal test--recent results and their validity. F. Pott. 1995;39(5):771-9. PubMed · Publisher

Abstract

The general experimental design of intraperitoneal (i.p.) carcinogenicity studies with inorganic fibres in rats is described. In a current study, in addition to glass microfibres, size-separated fine respirable fractions of commercial insulation wools (MMVF-11 and MMVF-21) also induced mesotheliomas after i.p. injection of 0.4 x 10(9) fibres. These fibre samples were also tested in inhalation studies. A special glass fibre type (B-01), which is of interest because of its low biodurability, induced tumours with 25- and 50-fold higher doses. The i.p. model has been proved to be much more specific and sensitive for testing the carcinogenicity of inorganic fibres than the inhalation model. Objections to this conclusion are cited and discussed with alternative arguments.
Malignant mesothelioma and duration of asbestos exposure: correlation with tissue mineral fibre content. V.L. Roggli. 1995;39(3):363-74. PubMed · Publisher

Abstract

Among 441 cases of malignant mesothelioma in the author's files, there were 324 for whom reliable information was available regarding the duration of exposure to asbestos. Included were 298 pleural and 26 peritoneal mesotheliomas. The mean duration of exposure to asbestos was 23 +/- 14 years for all cases, and was not different for the pleural and peritoneal groups. Lung tissue was available for analysis of mineral fibre content in 94 cases. Linear regression analysis showed a significant correlation between duration of exposure and asbestos bodies per gramme of wet lung as determined by light microscopy, and between duration of exposure and total uncoated fibres (5 microns or greater in length) as well as commercial amphibole fibres per gramme as determined by scanning electron microscopy (P < 0.05). Individuals with direct exposures had on average higher asbestos contents than patients with indirect exposures. Furthermore, for each duration of exposure, shipyard workers had on average higher asbestos contents than non-shipyard workers (P < 0.05). Mesotheliomas are associated with a wide range of durations of exposure to asbestos and pulmonary asbestos burdens, and there is a rough correlation between duration of exposure and pulmonary commercial amphibole content.
Statistical analysis of results of carcinogenicity studies of synthetic vitreous fibres at Research and Consulting Company, Geneva. C.E. Rossiter, J.R. Chase. 1995;39(5):759-69. PubMed · Publisher

Abstract

Five inhalation studies of synthetic vitreous fibres have recently investigated experimental tumorigenic responses to four different refractory ceramic fibres (RCF), two fibre glasses, one stone (rock) wool and one slag wool. Except for one RCF, the source materials were typical commercial products. Three studies included positive control groups exposed to chrysotile or crocidolite asbestos. The studies were conducted using state-of-the-art technologies for fibre size separation, fibre lofting and nose-only inhalation exposure. The target average fibre size was 20 microns long by 1 micron diameter. Hamsters exposed to a kaolin RCF yielded a mesothelioma rate of 38%, but no lung cancers. There were no tumours among the chrysotile-exposed hamsters. At the highest dose of 30 mg m-3 in rat studies, the commercial RCF all produced significant numbers of lung tumours, and some mesotheliomas. The fourth RCF, which had been heat-treated to simulate an after-service fibre, did not produce a significant excess of lung cancers, but did produce one mesothelioma. A rat multi-dose experiment with three lower doses of the kaolin RCF yielded one mesothelioma among 379 rats, but no excess of lung tumours. The overall dose-response relation for lung cancer did not appear to be linear, consistent with the possibility of a threshold close to the Maximum Tolerated Dose. No insulation wool (glass, stone or slag) exposure group had a lung tumour rate that differed statistically significantly from the tumour rate for the respective concurrent control groups, sham-exposed to filtered air. There was no significant difference in the total tumour rates between the four insulation wool groups and the control animals, and no significant dose-response relation above the respective sham-exposed control tumour rates. The total lung tumour rates for rats in both chrysotile and crocidolite exposure groups were significantly raised. One animal in each asbestos-exposed group developed a mesothelioma, whereas no air control or insulation wool-exposed animal did so.
The in vivo biological activity of ceramic fibres. R.C. Brown, J.A. Hoskins, L.R. Glass. 1995;39(5):705-13. PubMed · Publisher

Abstract

The well-known health effects following exposure to amphibole asbestos have led to some concern about the potential for other fibrous materials to cause similar diseases. This paper presents a summary of some of the inhalation experiments conducted with ceramic fibres in both rats and hamsters at the Research and Consulting Company, Geneva. One ceramic fibre (designated RCF1) was tested in rats at four exposure levels, this fibre was also tested in hamsters. Three other fibres were only tested in rats at the highest level--30 mg m-3. The increased incidence of tumours in these experiments has been contrasted with the negative results obtained with glass or mineral wools. However, there is evidence that the ceramic fibres were longer than the glass fibres and that long ceramic fibres were retained in lung tissue to a greater extent. This is sufficient to explain the results without recourse to explanations based on chemical differences between fibres.
Airborne concentrations of asbestos in non-occupational environments. M. Corn. 1994;38(4):495-502, 410. PubMed · Publisher

Abstract

Concentrations of asbestos in air were determined from analysis of samples collected in over 300 buildings involved in litigation. Samples were collected by certified industrial hygienists and analysed in certified laboratories by transmission electron microscopy. Building group mean concentrations of asbestos in building air inhaled by occupants were generally less than 0.0005 f ml-5 > 5 microns (90th percentile). At these concentrations the risk from asbestos exposure would be very low for building occupants. Another data set was obtained from the maintenance logs kept by owners of buildings containing asbestos fireproofing and subject to Operations and Maintenance Programmes to evaluate asbestos inhalation risk to maintenance workers. The logs were kept to document protective measures and maintenance personnel exposures during 1991-1992. Data are presented for one commercial building, which is typical of data for three additional commercial buildings and a medical centre. All samples were evaluated by the NIOSH 1400 protocol for sampling and analysis by phase contrast microscopy. Operations and maintenance precautions to reduce dust emission were modest; they included spraying of ceiling tiles with amended water, HEPA vacuuming tile edges before entry and after tile replacement, respirator usage and careful work. Negative pressure containment was not used. In this building personal exposures in electrical/plumbing work ranged from 0.000 to 0.035 f ml-1 > 5 microns in length (average work time of one job was 118 min); the 8-h TWA was 0.0149 f ml-1 > 5 microns.(ABSTRACT TRUNCATED AT 250 WORDS)
Asbestos use and carcinogenicity in Germany and a comparison with animal studies. F. Pott. 1994;38(4):589-600, 420. PubMed · Publisher

Abstract

The centralized structure of economic affairs in the former German Democratic Republic (East Germany) and the isolation from the free market led to the situation that imported asbestos was almost exclusively chrysotile. More than 90% came from the Kiembay mining area in the Ural Mountains, and about 7% was long-fibre chrysotile from Canada. Sturm and co-workers detected 1082 mesothelioma cases from 1960 to 1990 in the counties of Magdeburg and Halle. In 843 of these cases an exposure to asbestos was evident. Seventy-two cases were exposed to chrysotile only. Suspected exposure to amphiboles imported before World War II or to fibre contained in talc could not be substantiated. Up to now, there have been no analyses of lung fibre burdens from such cases. Reviewing the carcinogenicity studies in rats performed by inhalation or intra-cavitary injection of chrysotile, amosite and crocidolite fibres, the results give no clear indication of a lower carcinogenic potency per chrysotile fibre than per amphibole fibre if equal fibre numbers and fibre sizes are applied, although the chrysotile content of the lungs is relatively low. Also the mesothelioma rates after inhalation exposure to extremely high concentrations of the different asbestos fibre types are similar for chrysotile and the amphiboles and in the region of 5%. Compared with the asbestos-related cancer rates in chrysotile textile workers, rats have to be exposed to a more than 100-fold higher fibre concentration than humans to induce the same lung tumour incidence.
Biological effects: asbestos-cement manufacturing. H. Weill. 1994;38(4):533-8, 413. PubMed · Publisher

Abstract

Fourteen cohorts of asbestos-cement workers have been studied. These studies have demonstrated exposure-response relationships for lung cancer, mesothelioma and asbestosis. For lung cancer, relatively consistent results have been observed, with risk two-fold or less in 13 of the 14 cohorts. Among New Orleans workers, excess risk was restricted to those with X-ray evidence of asbestosis. Workers employed at least 21 years but without X-ray abnormalities, experienced no elevated risk, while those with small opacities (1/0 or higher) had substantially elevated risk (SMR > 400). Exposures in these two groups had been similar. These results suggest that asbestosis may be a necessary precursor for asbestos-induced lung cancer; if so, then the no-threshold model for lung cancer risk is inappropriate since there is general agreement that very low exposures will not result in radiologically detectable lung fibrosis. Further data on this potential link are needed. As in other industries, mesothelioma risk was strongly related to amphibole exposure, especially to crocidolite in asbestos-cement pipe manufacture. A cluster of cases has recently been reported in a family amosite-cement business. Among New Orleans workers, risk of asbestosis was related to cumulative exposure but there was little evidence of risk below 30 f ml-1-years. Progression of asbestosis in these workers was slow, related to past cumulative exposure and not related to lung function decline. Asbestosis risk is therefore not likely to develop in workers under current controlled exposure conditions.
Biological indicators of chrysotile exposure. B.W. Case. 1994;38(4):503-18, 410-1. PubMed · Publisher

Abstract

Chrysotile asbestos is retained in lung tissue, where it may be used as a marker of exposure. Studies include analysis of sputum and bronchoalveolar lavage fluid, but principally lung parenchyma from autopsy or surgically resected specimens. Asbestos bodies form on chrysotile fibres but are generally not a good indicator of human exposure to chrysotile because of their greater probability of formation on amphiboles. Chrysotile fibre analyses in lung have advantages and limitations. Chrysotile concentration is related to the level of environmental and occupational exposure, but in the latter situation owing to deposition, fibre alteration and clearance cumulative exposure and interval between end-exposure and death clearly affect results. Autopsy case series are biased toward increased proportions of asbestos-related diseases as compared to epidemiological cohort data. Analytical problems include potential contamination by chrysotile at autopsy, from fixatives, from post-fixative processing and in the analytical laboratory itself. These may have greatest effect in studies of individuals with low exposure, for tissue other than lung, and for short chrysotile fibres. Selection of control subjects should be contemporaneous with that of cases, and control subjects should fully reflect the hospital population at the time of case death. Limited data are available on fibre analysis in pleural tissue. More are needed. Issues requiring attention include avoidance of contamination, selection of controls, and sample site selection (parietal pleura, or tumour or plaque). For mesothelioma, two case-control studies of lung fibre burden show the principal relationship to be with long amphiboles, but some methodological problems exist. Lung cancer shows no such fibre-type differences. Asbestosis seems to be associated with long-fibre chrysotile and tremolite in one study and short fibres in others. Overall, lung retained dose is a useful indicator of chrysotile exposure if used cautiously in inference, and is very useful in the evaluation of historical exposures and industrial hygiene data in epidemiological studies.
Cancer mortality in chrysotile mining and milling: exposure-response. D. Liddell. 1994;38(4):519-23, 412. PubMed · Publisher

Abstract

New material was presented from pending publications arising from the follow-up to 1988 of the Quebec cohort of over 10,000 chrysotile miners and millers born 1891-1920. In reviewing these and previous findings, the following conclusions were drawn; they are supported, insofar as this is possible, by the only other relevant information, that from Balangero, in Northern Italy. There is strong evidence that the risk of lung cancer as a result of exposure to chrysotile at concentrations of less than 15 million particles per cubic foot is vanishingly small. At higher concentrations, the relative risk of lung cancer is elevated, but less so in smokers of 20 or more cigarettes a day than in others. The magnitude of this risk cannot be evaluated with any certainty, but this is unimportant as these higher concentrations (above about 50 f ml-1) are well outside the range of experience nowadays. There is no evidence that the risk of laryngeal cancer or of stomach cancer are adversely affected by exposure to chrysotile. Nor is there evidence of increased risks of other abdominal malignancies or of kidney cancer among chrysotile miners and millers. The risk of mesothelioma in chrysotile miners and millers is very low compared with the risks in populations exposed to amphiboles or to mixtures of fibres including even small proportions of amphiboles.
Carcinogenesis and related cell and tissue responses to asbestos: a review. B.T. Mossman. 1994;38(4):617-24, 423. Review PubMed · Publisher

Abstract

A review of the literature reveals that chrysotile asbestos has a mulitiplicity of effects on cells and tissues which can provide a framework for assessment of its role(s) in initiation, promotion, or as a co-carcinogen which acts in concert with chemical carcinogens found in cigarette smoke in the development of lung cancer. Several caveats important in the interpretation of these data include the general lack of dose-response protocols both for in vivo and for in vitro studies as well as the absence, in many studies, of minerals which are appropriate positive or negative controls based on epidemiological data in man. Other factors which may account for disparities in results between studies include the use of different preparations of chrysotile fibres with distinct chemical and physical compositions and different cell types and species. Whether chrysotile is an initiator of lung cancer or mesothelioma in human cells is unclear, as evidence of chromosomal aberrations in human bronchial epithelial cells are for the most part negative (Kodoma et al., 1993; see Mossman, B., this Workshop): only one study employing pleural mesothelial cells from four individuals, two of whom exhibited chromosomal abnormalities before exposure to asbestos, has documented chromosomal changes with chrysotile, crocidolite and amosite asbestos, and this study did not use a non-pathogenic dust as a negative control. Studies using human lymphocytes show chromosomal changes after exposure to latex beads or chrysotile at equal weight concentrations (Korkina et al., 1992; see Mossman, B., this Workshop). Lastly, although both chrysotile and crocidolite asbestos demonstrated dose-dependent increase in aberrant anaphases in an SV40 T antigen-transformed human mesothelial cell line (Pelin et al., 1992, see Mossman, B., this Workshop), erionite, a potent mesotheliomagenic fibre in rodents and humans, caused no aberrations in this bioassay. Several studies have been performed to determine the interactions of chrysotile with rodent cells or isolated bacterial DNA. Results in a number of bioassays have been positive, but chrysotile is less potent on a fibre number comparative basis than crocidolite and no-observed-effect-levels (NOELs) have been observed in several systems. Cell proliferation by asbestos may be a more relevant phenomenon to tumour development and promotion, and the ability of chrysotile to stimulate cell proliferation, using a number of biomarkers, has been demonstrated both in vitro and after inhalation by rats.(ABSTRACT TRUNCATED AT 400 WORDS)
Chrysotile: its occurrence and properties as variables controlling biological effects. A.M. Langer, R.P. Nolan. 1994;38(4):427-51, 407. PubMed · Publisher

Abstract

Chrysotile formation arises through serpentinization of ultramafics and silicified dolomitic limestones. Rock types tend to control the trace metal content and both the nature and amounts of admixed minerals in the ore, such as fibrous brucite (nemalite) and tremolite. Some associated minerals and trace metals are thought to play a role in biological potential. Tremolite, one of the important associated minerals, may occur with different morphological forms, called habits. These habits range from asbestiform (tremolite asbestos) to common blocky or non-fibrous form (tremolite cleavage fragments). The latter is most common in nature. Tremolite in chrysotile ore varies in habit and concentration, both factors determining the degree of risk following inhalation. Tremolite fibre is thought to be important in relation to the occurrence of mesothelioma. Chrysotile fibrils may vary in diameter. Dust clouds generated following manipulation vary in fibre number and surface area. Chrysotile fibres exhibit a range of physical characteristics. The fibre may be non-flexible ('stiff') and low in tensile strength ('brittle'), and may lack an ability to curl. This fibre, referred to as 'harsh', sheds water more quickly than its curly, flexible 'soft' variety. The behaviour of the harsh fibres is more amphibole-like and their splintery nature suggests an enhanced inhalation potential. Slip fibre ore from Canada tends to contain more fibrous brucite (nemalite) than cross-fibre ore in the same mine. Industrial manipulation, which includes chemical treatment, heating and milling, may impart new surface properties to chrysotile dusts. Biological potential may be enhanced (opening of fibre bundles) or reduced (disruption of surface bonds and lessened ability to interact with organic moieties). Leaching of magnesium from chrysotile occurs at a pH less than about 10. Chrysotile has been demonstrated to lose magnesium in vivo and undergo clearance from the lung. The biological potential of magnesium-depleted chrysotile is much reduced, or even eliminated. Reduction of mesothelioma-inducing and cytotoxic potential has been observed and quantified experimentally. Use of chrysotile products in high-temperature environments may heat the mineral to the point where it undergoes alteration of properties, especially by dehydroxylation. Chrysotile ore may vary in properties and associated minerals: it may form aerosols with different size distributions, especially fibre/fibril diameters and surface areas; it may be associated with varying quantities of tremolite (with differing habits); it may be manipulated both industrially and environmentally to yield surfaces with different properties and, hence, differing biological potentials. Chrysotile's properties may vary from place to place and among different user industries.
Deposition and clearance of chrysotile asbestos. A. Churg. 1994;38(4):625-33, 424-5. PubMed · Publisher

Abstract

Studies of human lungs indicate that, for virtually all types of exposure, the relative proportion of amphibole asbestos retained in the lung far exceeds the proportion in the original dust and, conversely, the relative proportion of chrysotile is far less than that in the original dust. Although amphiboles appear to accumulate in lung in proportion to exposure and chrysotile does not, failure of chrysotile deposition is probably not the reason for the disproportionate retention of amphibole fibres. The available data suggest that chrysotile is deposited in the parenchyma but is cleared extremely rapidly, with the vast bulk of fibres removed from human lungs within weeks to months after inhalation; by comparison, amphibole clearance half-lives are of the order of years to decades. The mechanisms of preferential chrysotile clearance remain uncertain, but fragmentation of chrysotile into short fibres, possibly accompanied by extremely rapid dissolution of such fibres, appears to be important in this process. Chrysotile fibres do penetrate to the periphery of the lung, so that differences in mesothelial pathogenicity of chrysotile and amphiboles in regard to mesothelioma are not caused by failure of chrysotile to reach the pleura. The theory that the tremolite contaminant rather than the chrysotile itself is the cause of 'chrysotile-induced' disease (especially mesothelioma) is consistent with the available human data, but the contrary ideas that disease is caused either by the total transient burden of inhaled chrysotile fibres or by a small, sequestered, long-retained fraction of chrysotile fibres still need to be excluded.
Development of the Regular Interlaboratory Counting Exchanges (RICE) scheme to include visual reference counts and samples from asbestos clearance operations. P.W. Brown, N.P. Crawford, A.D. Jones, et al. 1994;38(5):687-703. PubMed · Publisher

Abstract

The RICE proficiency testing scheme for asbestos fibre counting operated until 1992 with industrial samples and with reference counts produced by an image analyser (Magiscan). The visual counts produced in RICE by the participating laboratories have now been used to develop a reliable reference count for these industrial samples. Concurrently with the routine participation in RICE, laboratories also counted samples from asbestos clearance operations; these counts were used to develop suitable reference counts and performance limits for this type of sample. The width of this satisfactory performance interval is proportional to the natural variation in the data on the samples and is therefore a fixed interval on the log scale (of sample density) for high density samples and a fixed interval on the square-root scale for low density samples (where counting normally stops after a fixed number of fields). These developments led to the introduction of visual reference counts and clearance samples into RICE during 1992.
Editor's preface to the report of the workshop on health risks associated with chrysotile asbestos. J.M. Ellison. 1994;38(4):397-8. Editorial · Historical article PubMed · Publisher
Human evidence: lung cancer mortality risk from chrysotile exposure. J.M. Hughes. 1994;38(4):555-60, 415-6. PubMed · Publisher

Abstract

The linear, no-threshold model is commonly used for estimating lifetime lung cancer risk from asbestos exposures. Studies of chrysotile workers have observed shallow slopes for the exposure-response relationship for miners/millers, friction products manufacturing workers and asbestos-cement (primarily chrysotile) workers but a steeper slope (approximately 16 times higher) for textile workers. For chrysotile exposures in buildings, where short fibres constitute the great majority of the fibres, the shallow slope is judged more appropriate. Using this slope the data regarding exposure levels to building occupants and maintenance workers, the annualized risks of lung cancer would be approximately 0.01 and 0.6 per million for these groups, respectively. Using the higher slope would result in risks 16 times higher, still considerably lower than those commonly accepted. Contrary to the model's assumption of increased risk for any amount of exposure, a number of studies have demonstrated evidence that lung cancer risk is not associated with years exposed to low exposure levels. Moreover, the accumulating evidence that asbestos-induced lung cancer may require lung fibrosis suggests a practical threshold since detectable lung fibrosis will not result from environmental exposure levels. Evidence suggests that the relative risk to non-smokers bay be slightly higher than to smokers (by a factor of 1.8). However, if this is true, this has little effect on risk assessment due to the low absolute risk in non-smokers. Tremolite has been associated with an increased risk of lung cancer in a study of vermiculite miners; the slope of the exposure-response relationship was similar to that for crocidolite miners and much higher than that of chrysotile miners. In spite of a recent report indicating that asbestos-associated lung cancer risk may be limited only to adenocarcinomas, the bulk of the evidence fails to confirm this.
Levels of workplace exposure. A.L. Rickards. 1994;38(4):469-75, 409. PubMed · Publisher

Abstract

A brief description was presented of the evolution of workplace exposure monitoring. Measurements began in the 1930s and developed through particle counting to the introduction of the membrane filter, light microscope method in the mid-1960s. It is important to be aware that most data from the past were collected in relation to workplace control. The membrane filter phase contrast microscope method provides an index of exposure. Fibres with diameters less than 0.2 microns are unlikely to be counted. The method is not capable of analysing individual fibre types and consequently all fibres are counted. There have been several changes to the detail of the membrane filter method. The possible effect of these changes were presented. The Asbestos International Association (AIA) has implemented a fibre counting performance trial and also an annual return of workplace monitoring data. A WHO project is in progress with the objective of harmonizing the membrane filter method for fibre counting of all fibre types using phase contrast microscopy.
Lung cancer mortality among asbestos textile workers: a review and update. J.M. Dement, D.P. Brown. 1994;38(4):525-32, 412. PubMed · Publisher

Abstract

In an update of the mortality of the cohort of 1200 South Carolina textile workers, of whom almost half died, there were 185 excess deaths (SMR = 1.44), which included 71 cardiovascular diseases (SMR = 1.37), 43 non-malignant respiratory diseases (SMR = 2.25) and 41 lung cancers (SMR = 2.25). Only two definite mesotheliomas were observed. Other possible cases may have occurred but no confirmatory pathology was available. Strong exposure-response relationships have been found for lung cancer and for non-malignant respiratory diseases. The data suggest a doubling of the lung cancer risk at an exposure of approximately 30 fibre years. Mortality from pneumoconiosis and other respiratory diseases was elevated at even the lowest cumulative exposure category (< 2 f ml-1 years). A nested case-control analysis failed to demonstrate a significant role for mineral oil exposure in the etiology of lung cancer. Differences in airborne fibre sizes may be important in explaining different lung cancer and pneumoconiosis risks in various industries. In particular, the data on airborne fibres in textile manufacturing industries suggested 11-27% were longer than 5 microns compared to 2-5% for mining and milling.
Macrophage-associated responses to chrysotile. G. Oberdörster. 1994;38(4):601-15, 421-2. PubMed · Publisher

Abstract

The different pulmonary macrophage (airway macrophages, alveolar macrophages, interstitial macrophages, intravascular macrophages, pleural macrophages) are an important part of the lungs' defences against non-fibrous and fibrous particles deposited by inhalation. The first line of defence is airway macrophages and alveolar macrophages (AM) which initially interact with deposited chrysotile fibres and subsequently release a number of mediators including growth regulatory and chemotactic proteins, arachidonic acid metabolites, proteases, NO and active oxygen species, all of which can affect--also adversely--specific target cells in the lung. Mechanical clearance via the mucociliary escalator and dissolution of phagocytized fibres in the acidic milieu of the phagolysosome in pulmonary macrophages are further important functions of AM. Chrysotile appears to be more toxic or at least has the same toxicity to AM as amphibole fibres when doses of a similar mass are administered. However, on a fibre number basis chrysotile appears to be less toxic to AM. The importance of the appropriate dose parameter--i.e. fibre mass, number or surface area--needs to be considered in in vitro as well as in in vivo studies. Short chrysotile fibres are cleared from rat lungs very rapidly whereas longer ones are cleared at a much slower rate. This is due to efficient phagocytosis of short fibres by AM accompanied by dissolution in the acidic milieu of the phagolysosome. Prediction of chrysotile clearance in primate lung based on results from rat studies result in an overall retention half-time of approximately 105 days, based on which no long-term accumulation of chrysotile in the primate lung is to be expected. Long-term inhalation studies in baboons exposed to chrysotile confirm the very fast build up of a low steady-state lung burden, consistent with a pulmonary retention half-time for chrysotile of approximately 90 days. Despite the fast clearance and low pulmonary accumulation of chrysotile, the resulting effects, such as asbestosis, were found to be of the same severity in rats as those induced by amphibole exposure. In the amphibole-exposed rats, the fibre lung burden continued to increase with exposure time. The potential contamination of chrysotile with tremolite cannot explain these results since there was no increased pulmonary accumulation of fibres in the chrysotile-exposed rats. Effects due to lung particle overload are not to be expected in long-term chrysotile inhalation studies since no accumulation occurs and one needs to distinguish clearly between a volumetric overload of the AM (not occurring with chrysotile) and failed or partial phagocytosis of long fibres.(ABSTRACT TRUNCATED AT 400 WORDS)
Mesothelioma among car mechanics?. H.J. Woitowitz, K. Rödelsperger. 1994;38(4):635-8. PubMed · Publisher

Summary

This paper, read at a 1993 workshop on health risks of chrysotile asbestos, reported the final results on car mechanics from a completed German case-control study of mesothelioma. Of 324 mesothelioma cases, 16 (4.9%) were classified as motor vehicle mechanics. This compared with 16 (5.1%) of 315 hospital controls, who were patients who had undergone lung resection for other reasons (mostly lung cancer), and 12 (6.6%) of 182 population controls. Employment as mechanics began between 1925 and 1972. The median start year was 1949 for cases and hospital controls and 1946 for population controls, and median duration was longer for controls than for cases. Some mechanics in each group reported brake repair work: six or seven cases (the text and table differ), nine hospital controls and three population controls. In all three groups some individuals had substantial asbestos exposure in other jobs, such as power plants or shipbuilding. Four cases had no history of other asbestos exposure, and three of these had done brake repairs. Lung tissue analysis was available for two cases and one hospital control. It found no fibres longer than 5 µm in one case, amphibole fibres in the other case, and numerous long chrysotile fibres in the control. The authors concluded that there was no evidence of an increased mesothelioma risk for car mechanics, even with brake repairs. They added that asbestos exposure in other employment was an important confounder, so a small risk would not be detectable.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Mesotheliomas and chrysotile. P. Elmes. 1994;38(4):547-53, 415. PubMed · Publisher

Abstract

Mesotheliomas are rare. While most are reported to be associated with exposure to durable fibres, a proportion are not caused by the inhalation of fibres at all. Reports of individual cases and studies of small groups are unreliable as evidence of cause because: (a) diagnosis is often unreliable; (b) even if chrysotile fibres are found in lung tissues, the mesothelioma may still be spontaneous. Present knowledge has not progressed much since 1964 when the absence of cases of mesothelioma in amosite and chrysotile miners in South Africa and the very low incidence in Canadian mines was known but not believed. Now we know this information was correct. The significance of low-level amphibole exposures in predominantly chrysotile mixes was not appreciated until studies of fibres in lungs using electron microscopy showed the high lung burden of amphibole fibres in the 1970s and 1980s. The effect of these findings is to make most European and U.S.A. factory cohorts inappropriate for the evaluation of chrysotile mesothelioma risk. Reviewing the current evidence published and unpublished, it seems likely that chrysotile uncontaminated by tremolite may not have caused any mesotheliomas even at high cumulative life-time exposures. Information on the mesothelioma risk among chrysotile user populations using fibres not containing tremolite is badly needed.
Mortality and cancer incidence of workers exposed to chrysotile asbestos in the friction-products industry. G. Berry. 1994;38(4):539-46, 413. PubMed · Publisher

Abstract

Three studies provide data on this topic. The largest was at the Ferodo factory in the U.K. There was no evidence of an overall excess in mortality from all causes, and in particular no increase in mortality due to lung cancer. Also, there was no evidence of any dose-response effect for lung cancer. There were 13 mesotheliomas but for 10 of these there had been exposure to crocidolite whilst working on a special contract that only a small minority of the workforce were involved in. Another one had worked in an asbestos-cement factory for 20 years. This left two mesotheliomas, one unconfirmed, for which the only known exposure was to chrysotile asbestos. The second study was of a plant in Connecticut. There was a significant increase in mortality due to respiratory cancer, but this excess was greatest in those with less than 1 year's exposure and was unrelated to cumulative exposure. No mesotheliomas occurred. The third study was of two factories in Ontario manufacturing automotive components. There was a non-significant increase in lung cancer mortality but the majority of these had not worked in the departments where asbestos was used. There were two unconfirmed mesotheliomas, one of whom had worked with friction materials. In conclusion, the three studies show that, if there are any effects on mortality due to working in the manufacture of friction materials, these effects must be small.
Nature of exposure to chrysotile. M. Lippmann. 1994;38(4):459-67, 408. PubMed · Publisher

Abstract

Fibres in general, and chrysotile fibres in particular, have properties that set them apart from other airborne particles in terms of their aerodynamic behaviour and the nature of their interactions with cells and fluids in vivo. Their lengths and diameters are primary determinants of their penetration through conductive airways to deposition sites within the lungs, and to their access into translocation pathways; their surface properties and biopersistence affect their retention times and the biological responses that can lead to chronic disease. In the absence of sufficiently detailed knowledge of the specific ranges of lengths, diameters, surface properties and biopersistence of the long, thin fibres most closely related to hazard potential, crude surrogates of relevant exposure have been used. These include: (i) the number concentration of fibres (aspect ratio > 3) longer than 5 microns, as measured by optical microscopes lacking the ability to resolve thin (< 0.25 micron dia.) fibres; or (ii) by electron microscopy of mostly short, thin fibres by scanning a small fraction of the surface of the filter on which they have been collected. The conventional electron microscopy analytical protocols lack the ability to determine the presence of a statistically relevant number of the long fibres having the greatest hazard potential. A strategy for determining the distribution of long fibres of all thicknesses is outlined.
Other diseases in animals. J.M. Davis. 1994;38(4):581-7, 420. PubMed · Publisher

Abstract

Experimental inhalation in a number of studies has demonstrated that chrysotile asbestos can cause pulmonary fibrosis and both benign and malignant pulmonary tumours, two lesions which are associated in that the studies reporting high tumour rates also found high levels of asbestosis. One comparison reported that animals with malignant tumours had approximately twice the amount of fibrosis in the lung parenchyma as those of similar age without tumours. Many studies have examined the pathogenicity of asbestos administered by ingestion and most of these included chrysotile asbestos: the results have been universally negative apart from one study with amosite that contained no control animals and is best discarded. Only one inhalation study has reported an examination of the larynxes of animals: this found no pathological changes. In many studies, tumours other than the lung had been listed, but significant numbers of kidney tumours have never been recorded. Injection studies inducing mesothelioma have indicated that fibre geometry is important with long thin fibres (> 8 microns in length and < 0.25 microns in diameter) being the most carcinogenic. This has been difficult to confirm for inhaled fibres although fibres less than 5 microns in length appear to cause neither fibrosis nor pulmonary tumours. Similar results have been found with amosite for fibres up to 10-15 microns although longer fibres do produce these conditions. It is suggested that to produce pulmonary fibrosis and neoplasia fibres may need to be longer than 20 microns. Chrysotile has been shown in many studies to be removed from lung tissue much more rapidly than amphibole fibres.(ABSTRACT TRUNCATED AT 250 WORDS)
Symptoms and pulmonary functions as measures of morbidity. M.R. Becklake. 1994;38(4):569-80, 418. PubMed · Publisher

Abstract

A contemporary list of non-malignant respiratory conditions associated with exposure to environments contaminated by chrysotile asbestos dust includes pulmonary parenchymal and pleural fibrosis, small airway abnormality and conditions affecting the large airways such as chronic bronchitis and chronic airflow limitation. The first two are attributed to the specific biological effects of asbestos dust, the latter two to nonspecific effects of exposure to mineral dusts and/or other airborne pollutants in workplaces contaminated by asbestos dust. Prevalence rates for all the clinical markers of morbidity (radiographic change, lung function deficit and symptoms) have been shown to increase with increasing exposure to chrysotile but more steeply when exposure is in textile and other manufacturing plants than in mining and milling. The presence of amphiboles such as tremolite in the airborne dust may also result in steeper exposure-response relationships, while exposure in crocidolite mining results in very much steeper exposure-response relationships. Clinical asbestosis, though less frequent and less severe than previously, is still associated with increased moribidity, while localized pleural fibrosis in the form of plaques with minimal or no parenchymal fibrosis, currently the most frequently encountered non-malignant asbestos related condition encountered in clinical practice, may also be associated with morbidity, including lung function deficit. Determinants of progression of chrysotile-related parenchymal and pleural radiographic abnormality include duration and time since first exposure and, possibly, continued exposure after first appearance of radiographic changes. Progression of asbestos-related airway disease, documented as lung function loss over time, may, under the influence of continued exposure, be comparable to the progression observed under the influence of continued smoking.
The assessment of exposure in terms of fibres. G.W. Gibbs. 1994;38(4):477-87, 409-10. PubMed · Publisher

Abstract

The membrane filter (MF) method for evaluating asbestos fibre concentrations was introduced in the 1960s. Before that time the midget impinger (MI) was used in North America, while the long running (LRTP) and regular thermal precipitator (TP) were used in the U.K. All studies from which estimates of long-term health risks can be derived (i.e. those with individual cumulative lifetime exposure estimates) were based on the now obsolete methods. The reliability of converting these indices of exposure to MF equivalent concentrations was reviewed. It was concluded that no overall single factor could be derived for the Quebec mining and milling industry. However, it has been possible to derive conversion factors at the individual mill and work area level. Applying these in one Quebec mortality study analysis based on all jobs held by persons in the cohort gave an overall MF/MI ratio of 3.6. An examination of the confidence intervals surrounding the Quebec data, ratios derived for other chrysotile mines by other investigators, and measurements of fibre concentrations in the 1970s suggest that this was probably not unreasonable. Side-by-side and other measurements were used to convert MI concentrations in the U.S. textile industry to MF fibre concentrations. While conversions involve considerable uncertainty, independent measurements of fibres in the lung tissues of workers from the U.S. textile plant and Quebec mills show that in lungs the ratios of the concentrations of chrysotile to those of tremolite are quite consistent with the ratio of assessed exposures to these fibres in the two industries. There is an apparently higher risk of mesothelioma in one Quebec mining area (Thetford Mines) than in another (Asbestos). A high concentration of fibrous tremolite has been found in the lungs of workers in Thetford. A method of evaluating the extent to which mesothelioma risk in the chrysotile mining industry might be explained by tremolite exposures was proposed. The slope of the lung cancer dose-response relationship for the textile industry is approximately 50 times that for the mining and milling industry. Available data on the length distributions of fibres from Quebec mines and mills (up to 5% > 5 microns) and the Charleston textile plant (up to 21% > 5 microns) and some marginal indication of longer fibres in tissues from Charleston workers suggest that further work specifically addressing differences in the size distributions of long fibres in these industries is needed.
The human evidence: parenchymal and pleural changes. G. Hillerdal. 1994;38(4):561-7, 417. PubMed · Publisher

Abstract

Asbestos inhalation can cause fibrotic reactions both in the lung parenchyma and in the pleura. The incidence and relative proportions of these lesions in any cohort will be dependent on: (1) the time factor: both asbestosis and pleural plaques are progressive diseases and the longer the time from exposure, the more the changes; (2) the dose-response: the more intense the exposure, the earlier and the more advanced is the asbestosis. However, pleural plaques are only moderately dependent on the exposure level and will occur after approximately 30 years in most persons who develop them, even after fairly low exposure; (3) the early lesions are difficult to diagnose radiologically and are prone to overdiagnosis. Considerable caution is necessary when evaluating results if only such lesions are reported. It is generally accepted that the occurrence of radiological asbestosis is a risk factor, particularly for bronchial carcinoma. However, pleural plaques have been considered to be relatively harmless. Recent data have indicated, however, that they can be indicators of sufficient exposure to increase the risk of other asbestos-related diseases, including lung cancer and mesothelioma.
The removal of fibres of chrysotile asbestos from lung. A. Morgan. 1994;38(4):643-6. Letter PubMed · Publisher

Summary

In this letter, written after the Workshop on Health Risks Associated with Chrysotile Asbestos, the author addressed the uncertainty about why chrysotile fibres are removed from the lung more rapidly than amphibole asbestiform minerals, and in particular whether this is due to fibre dissolution or to clearance by macrophages. The author reviewed published evidence. Studies measuring magnesium/silicon ratios in fibres recovered from human and animal lungs gave conflicting results. Some reported magnesium depletions as high as 50%, and others found slight or no significant leaching. Radioactive tracer studies in rats had shown that about 30% of structural magnesium dissolved within 1 month of intrapleural injection, with slower leaching after that. Other rat studies showed greater leaching during the first month after intratracheal instillation, rapid removal of acid-leached fibres, and longitudinal splitting of fibres in the lung. The author discussed problems in interpreting Mg/Si ratios, including changes during fibre recovery and the limited resolution of analytical methods. Citing glass-fibre findings, the author suggested that chrysotile may dissolve faster in the lung than in the pleural or peritoneal cavities. Carcinogenicity comparisons based on intra-cavity injection might therefore not be relevant to lung cancer. The author concluded that the view that dissolution plays a very minimal role in human chrysotile clearance was difficult to sustain, that some fibres persist for years, and that further research was required.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
The uses of chrysotile. B.J. Pigg. 1994;38(4):453-8, 408. PubMed · Publisher

Abstract

Chrysotile asbestos was used in thousands of commercial products in the past. However, current usage is confined to four principal product categories. These are: asbestos cement; friction materials; roof coatings and cements; and gaskets. Current products, different from several friable products formerly in major use and discontinued some 20 years ago, in the majority of countries, have the asbestos locked-in or encapsulated within another matrix. With modern control measures, exposures are minimized throughout the product life cycle. Approximately 85% of chrysotile used worldwide is for production of asbestos-cement products (pipes and sheets). In 1992, approximately 28 million tones of asbestos-cement products were produced in approximately 100 countries.
Work environment of plants manufacturing asbestos-containing products in Japan. T. Higashi, H. Hori, H. Sakurai, et al. 1994;38(4):489-94, 409. PubMed · Publisher

Abstract

In 1985, a comprehensive study of asbestos-containing product plants (A/C, friction, textile) was performed. The data presented were based not on personal but on area sampling. A conversion equation from area sampling data to personal exposure values was developed. Exposure concentrations were 0.07-0.66 f ml-1. In workplaces which belonged to member companies of the Japan Asbestos Association, the percentage of workplaces whose exposure concentrations was less than 0.3 f ml-1 was 70% in 1985 (N = 510), but 98% in 1992 (N = 430). Concentrations in a new, well-controlled A/C plant were less than 0.1 f ml-1.
Workshop on the health risks associated with chrysotile asbestos: a brief review. M. Lippmann. 1994;38(4):639-42. Letter PubMed · Publisher
An empirical model for estimating the collection efficiency of dust-mist respirators. L.M. Brosseau, J.S. Evans, M.J. Ellenbecker. 1993;37(2):135-50. PubMed · Publisher

Abstract

This paper compares experimental measurements of filter performance with predictions of aerosol collection by dust-mist respirators using the single fibre efficiency model and an empirical model developed by the authors. The former, a theoretically-based semi-empirical model, indicates that mechanical phenomena such as impaction, interception and diffusion are responsible for only a fraction of the collection efficiency of dust-mist respirators, i.e. 30-70% depending on particle size. The difference between these relatively low predicted efficiencies and experimentally observed values, which were greater than 95%, can be attributed to electrostatic forces. Because it was not possible to determine filter fibre charge the single fibre efficiency model could not be used to predict electrostatic collection. An empirical model developed from experimental data with monodisperse latex aerosols was used to predict silica and asbestos collection. The empirical model adequately described silica collection, but predicted much higher asbestos penetration than was observed experimentally.
Asbestos induced oxidative injury to DNA. N. Mahmood, S.G. Khan, S. Ali, et al. 1993;37(3):315-9. PubMed · Publisher

Abstract

DNA-damaging effects of asbestos in the presence of organic peroxides and hydroperoxides were investigated. The destabilization of the secondary structure of DNA, damage to deoxyribose sugar and DNA fidelity were measured, respectively, by S-1 nuclease hydrolysis, the formation of thiobarbituric acid (TBA)-reacting species and a melting temperature (Tm) profile using calf thymus DNA. S-1 nuclease hydrolysis and Tm determinations have shown that the presence of benzoylperoxide (BOOB), cumene hydroperoxide (COOH) or tertiary-butyl hydroperoxide (t-BOOH) increased asbestos-mediated DNA damage by a large factor compared either to asbestos alone or to peroxide or hydroperoxide alone. However, no formation of TBA-reacting species could be observed in this system. The quenchers of reactive oxygen species (ROS) afforded protection against DNA damage. These results suggest that asbestos in the presence of organic peroxides and hydroperoxides damage the DNA which is mediated by the generation of oxygen free radicals. The significance of these results in relation to the development of cancer of the respiratory tract among the asbestos exposed population is discussed.
Ferruginous body counts in sputum as an index of past exposure to mineral fibres. J.C. McDonald, P. Sébastien, B. Case, et al. 1992;36(3):271-82. PubMed · Publisher

Abstract

Previous work by our group among vermiculite miners exposed to fibrous tremolite demonstrated that asbestos body counts in sputum closely reflected intensity and duration of past exposure. In the present project sputum samples from nearly 600 volunteers from 11 cohorts of workers exposed to asbestos and other mineral fibres were found to contain much lower numbers of asbestos bodies than had been observed in vermiculite workers and these counts did not reliably reflect past levels of exposure. No evidence was found that occupational exposure to man-made mineral fibres led to any ferruginous body formation. Asbestos body counts appeared to differentiate between mesothelioma cases and controls and between levels of radiological asbestosis, but in both comparisons, based on small numbers, the power of discrimination was low. Substantial variation was found both in asbestos body and in macrophage counts in daily sampling of vermiculite workers but it was not sufficient to invalidate comparison between groups for epidemiological study. In individual subjects, however, little reliance can be put on results from a single sputum sample, particularly if negative.
Fibrous dust release from asbestos substitutes in friction products. S.A. Jaffrey, A.P. Rood, R.M. Scott. 1992;36(2):173-81. PubMed · Publisher

Abstract

A small-scale study was carried out on friction and reinforcing materials containing Kevlar and glass fibres. Kevlar, an aramid fibre, and synthetic silicate fibres are being increasingly used in brake pads and shoes for cars and trucks. The fibre levels given out under abrasion in the laboratory were low. As a comparison, a brake pad containing asbestos was also tested and gave high levels of airborne fibres.
The classification of asbestos fibres by scanning electron microscopy and computer-digitizing tablet. S.F. Platek, R.D. Riley, S.D. Simon. 1992;36(2):155-71. PubMed · Publisher

Abstract

Because of the need to completely and accurately size asbestos bulk samples for toxicity studies, a method was developed to classify asbestos fibres using enlarged micrographs originally produced on the scanning electron microscope (SEM). Individual fibre length and width measurements were performed on a computer-assisted, digitizing tablet. This method, though time consuming, permitted the sizing of all fibres (length and width) and particles (area) in selected fields of view at SEM magnifications of x100 and x2500. Final enlargement of the micrographs permitted sizing magnifications of x10,000. Seven distinct asbestos samples were classified including five chrysotile and two crocidolite samples. Statistical analyses showed good interfilter fibre size correlation for all types of asbestos. In addition, it was determined that a representative sizing of all fibres and non-fibrous particles on a filter preparation could be performed using five sets of micrographs taken at a magnification of x2500 and enlarged to x10,000: an inverse square root transformation (-0.5 power) is needed to normalize the distributions of length and width.
An estimate of the rate at which crocidolite asbestos fibres are cleared from the lung. R.S. Du Toit. 1991;35(4):433-8. PubMed · Publisher

Abstract

The cumulative fibre exposure of 36 deceased persons who had been employed on crocidolite asbestos mines of the NW Cape was compared with their lung burden determined by fibre count by optical microscope. Allowance for the period which lapsed between date of last exposure and death revealed a lung clearance rate amounting to a half-life of about 6 years.
Factors affecting the interaction of asbestos fibres with mammalian cells: a study using cells in suspension. R.C. Brown, E.A. Sara, J.A. Hoskins, et al. 1991;35(1):25-34. PubMed · Publisher

Abstract

One of the earliest events in pathogenesis by mineral fibres must be an interaction between fibre and cell surfaces. Using a simple technique in which cells in suspension were incubated with fibres and adhesion monitored by separation on a density gradient it has been shown that such interactions occur through two distinct mechanisms. The first, a charge-mediated effect, occurs with positively charged fibres such as chrysotile asbestos. The second, with amphibole or glassy fibres, is mediated by fibronectin which first binds to the fibre. The bound protein then attaches to RGD receptors on the cell surface; calcium and magnesium ions are necessary for optimal adhesion. The RGD receptors bind to a tripeptide region on the protein and small peptides containing the RGD sequence block fibre-cell interaction. If the surface silanol groups on the fibre were chemically coupled to trialkylsilyl groups then interaction was slowed.
Study of the count-to-mass conversion factor for asbestos fibres in samples collected at the emissions of three industrial plants. S. Puledda, A. Marconi. 1991;35(5):517-24. PubMed · Publisher

Abstract

Count-to-mass conversion factors for asbestos fibres in the stack emissions of three industrial plants were calculated. Dust samples deriving from different working processes were collected downstream from the fabric-based filtration systems. Gravimetric measurements were carried out utilizing an X-ray diffraction procedure based on the use of a silver filter that permits the correction for X-ray absorption by the sample. The number of fibres covered by regulations ('Regulated fibres') (F) was counted by phase-contrast optical microscopy (PCOM) on a section of the same filter as had been used for gravimetric measurements. The values of the conversion factors vary widely, ranging from 0.4 x 10(3) to 4.9 x 10(3) fibers per microgram (F microgram -1) according to the working process involved. They are always less than 20 x 10(3) F microgram -1, the value specified in the EEC Directive 217/87 concerning the prevention of asbestos pollution in the environment.
Analysis of amphibole asbestos in chrysotile and other minerals. J. Addison, L.S. Davies. 1990;34(2):159-75. PubMed · Publisher

Abstract

Chrysotile asbestos and many other mineral raw materials contain amphibole minerals which may be asbestiform. There is currently no analytical method which will detect the presence of amphibole at sufficiently low limits to preclude the possibility of inadvertent exposure of persons handling these materials to hazardous airborne fibre concentrations. A method of chemical digestion of chrysotiles has been tested with regard to the determination of their tremolite contaminant content and this has been applied to a range of chrysotile and other minerals. The method improves the sensitivity of the amphibole analysis at least 10-fold giving detection limits of 0.01-0.05% in chrysotile by X-ray diffractometry (XRD). The difficulties arising from compositional and morphological variations are discussed in the context of the potential hazards from airborne fibres and the relative values of analyses by XRD, infrared spectrophotometry (IR) and electron microscopy. It is concluded that XRD and IR are useful as screening methods for the detection of amphibole in chrysotile but other materials should be analysed by optical or electron microscopy.
Evidence for an amphibole asbestos threshold exposure for asbestosis assessed by autopsy in South African asbestos miners. G.K. Sluis-Cremer, E. Hnizdo, R.S. du Toit. 1990;34(5):443-51. PubMed · Publisher

Abstract

In an attempt to determine whether there exists a threshold asbestos dose below which asbestosis does not occur, data on 807 men who had worked on amphibole asbestos mines and undergone autopsy were analysed. When exposure was expressed as fibre-years no asbestosis was found at autopsy when exposure was up to 2 fibre-years, even after 31-45 years of residence time. In the group exposed to greater than 2-5 fibre-years asbestosis was found. When exposure was expressed as average fibre concentration asbestosis occurred below 2 fibres per ml (f ml-1) and the prevalence increased with residence time. In conclusion, if a threshold dose for asbestosis does exist it is at approximately 2 fibre-years if off-shift exposure is ignored.
Lung dust analysis in the assessment of past exposure of man-made mineral fibre workers. J.C. McDonald, B.W. Case, P.E. Enterline, et al. 1990;34(5):427-41. PubMed · Publisher

Abstract

In the cohort of American MMMF workers reported by ENTERLINE et al. [Ann. occup. Hyg. 31, 625-656 (1987)] autopsies were recorded in 652 (13.5%) of 4840 deaths. Lung tissue samples were sought from all pathologists and obtained in 145 (22.2%), together with similar samples from 124 matched referents. Lung fibre counts by phase contrast microscopy were 60% higher (P less than 0.05) in workers than referents. Electron microscopy (ATEM) also showed more fibres of all kinds--MMMF, asbestos and other--but no convincing excess of any one type. Lung samples of only 26% of workers contained any MMMF, almost all siliceous in nature and in low concentration. There were too few cases of lung cancer (19) for any useful conclusion; however, in the plant with the highest lung cancer SMR (200), and a probable mesothelioma, amosite at greater than 1.0 fibres per micrograms (f micrograms-1) was found in four of six workers but in none of their matched referents. Although our findings contribute little to the interpretation of the results obtained by ENTERLINE et al. they indicate the potential value of tissue analyses in monitoring epidemiological studies of MMMF exposure.
Workplace protection factors of HSE approved negative pressure full-facepiece dust respirators during asbestos stripping: preliminary findings. S.N. Tannahill, R.J. Willey, M.H. Jackson. 1990;34(6):547-52. PubMed · Publisher

Abstract

This research was designed to evaluate the workplace protection factors of Health and Safety Executive Approved, negative pressure full-facepiece dust respirators, during asbestos stripping. A standard method to measure the concentration of asbestos fibres inside full-facepiece respirators has been developed and the workplace protection factors have been calculated from the data obtained. The respirators in this study are approved for use by the Health and Safety Executive in concentrations of up 900 times the Control Limit [HEALTH AND SAFETY EXECUTIVE, Guidance Note EH 41 (1985)] but the preliminary test results suggest that this level is inappropriately high for this type of respiratory protective equipment.

1980s

Effect of respiratory protective equipment on exposure to asbestos fibres during removal of asbestos insulation. H. Akkersdijk, C.F. Bremmer, C. Schliszka, et al. 1989;33(1):113-6. PubMed · Publisher

Abstract

Asbestos concentrations were measured within powered respirators used by workers involved in the removal of asbestos-containing insulation. Fibre concentrations within the protective gear appeared to be above the Dutch threshold limit value for crocidolite (0.2 f cm-3). Possible sources of exposure were analysed and measures were taken to improve the situation. After this, the fibre concentrations in the breathing area were reduced and were below the Dutch concentration limit.
Review of the significance of fibre size in fibre-related lung disease: a centrifuge cell for preparing accurate microscope-evaluation specimens from slurries used in inoculation studies. V. Timbrell. 1989;33(4):483-505. Review PubMed · Publisher

Abstract

Intratracheal, intrapleural and intraperitoneal inoculation studies in animals are widely used for identifying important factors in the pathogenicity of fine fibrous particles and estimating the potential of new materials to produce human pulmonary disease. Evidence on the significance of fibre size is reviewed, with emphasis on direct data derived from airborne fibres in asbestos mines and fibres retained in the mineworkers' lungs. This evidence indicates a need in mesothelioma-related inoculation experiments for means of measuring fibres down to 0.01 microns in diameter. A test cell, developed for preparing microscope-evaluation specimens from injection slurries, has a sector-shaped sedimentation chamber and is used in a swing-rotor centrifuge. To minimize re-formation of aggregates that are dispersed by shearing forces during sedimentation, a sample of the slurry is diluted beforehand to a degree indicated by the length of the longest fibres seen in the light microscope. Fibres and other particles are collected as a uniform deposit on a collodion film enveloping a microscope cover-glass. Current techniques are used to prepare specimens from films for light microscopy, scanning electron microscopy and the transmission electron microscopy which is so necessary for measurement of very fine fibres. Applications of the cell to fibre samples from other sources are outlined.
Urinary fibres in occupational exposure to asbestos. M.P. Guillemin, G. Litzistorf, P.A. Buffat. 1989;33(2):219-33. PubMed · Publisher

Abstract

Urine samples from 10 workers from an asbestos cement factory and from a control group of 10 workers from a foundry, were obtained; drastic precautions were taken to avoid contamination. Each urinary mineral fibre was sized and identified by transmission electron microscopy. Results show that contamination problems encountered by other authors have been overcome and that the workers exposed to chrysotile appear to excrete more chrysotile fibres, but that this difference is not statistically significant. Possibly only a few of the exposed workers are significantly exposed to asbestos, the overall exposure level being very low. The degradability of chrysotile fibres in biological fluids or the retention of fibres in some organ could explain the lack of apparent correlation between exposure and urinary concentration. Unexpectedly high concentrations of crocidolite fibres of unknown origin were detected in both groups of workers.
Personal exposure to asbestos dust during clearance certification. S. Bailey, A. Conchie, D.M. Hiett, et al. 1988;32(3):423-6. PubMed · Publisher
A comparison of fibre counting stopping rules in the application of the membrane filter method. N.P. Crawford, W.M. Maclaren, P. Brown, et al. 1987;31(1):53-66. PubMed · Publisher
A hypothesis concerning asbestos carcinogenicity: the migration of lipophilic carcinogens in adsorbed lipid bilayers. P. Gerde, P. Scholander. 1987;31(3):395-400. PubMed · Publisher

Abstract

The adsorption of phospholipids from lung surfactant onto inhaled asbestos fibres may create a unique opportunity for lipophilic carcinogens of tobacco smoke, e.g. polycyclic aromatic hydrocarbons (PAH), to diffuse within an all-lipid environment across the aqueous regions of the bronchial lining layer into the cellular membranes of the bronchial epithelium. This suggested 'lipid-link' mechanism can give very local but extremely high cellular doses of carcinogens at the preferential sites of asbestos and smoke deposition in the lung. Consequently, this may contribute to the strong synergism observed between smoking and asbestos exposure for the induction of bronchial cancer.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
A study of the length and diameter of fibres, in lung and in broncho-alveolar lavage fluid, following exposure of rats to chrysotile asbestos. E. Kauffer, J.C. Vigneron, A. Hesbert, et al. 1987;31(2):233-40. PubMed · Publisher

Abstract

This paper describes changes in the dimensions of fibres in the lungs of rats and in fibres removed from the lungs by broncho-alveolar lavage, following a single inhalation exposure to about 5 mg m-3 of chrysotile asbestos for 5 h. The lengths and diameters of fibres were measured with the transmission electron microscope. In the 90-day period following exposure, there was a progressive increase in the mean length and decrease in the mean diameter of fibres in the lungs. For fibres recovered by broncho-alveolar lavage, both the mean length and diameter decreased with time. These findings indicate that short fibres are cleared preferentially from the lung and that chrysotile fibres progressively separate into individual fibrils.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This was an animal experiment by INRS in France. Forty-eight male Sprague Dawley rats, in six groups of eight, breathed UICC Canadian chrysotile asbestos once, for 5 hours, at about 5 milligrams per cubic metre. Matching control rats breathed clean filtered air. Rats were killed at the end of exposure and 1, 7, 28 and 90 days later. Fibres in one lung lobe and in fluid washed out of the lungs (lavage) were measured by electron microscope. In the lung lobe, average fibre length rose from 5.1 to 8.6 micrometres over 90 days, and average diameter fell from 75.0 to 47.6 nanometres. In lavage fluid, both fell: length from 4.6 to 2.0 micrometres, diameter from 72.1 to 43.3 nanometres. Fibres shorter than 5 micrometres made up a falling share of lung fibres and a rising share of lavage fibres. Exposed rats had significantly more neutrophils in lavage fluid on days 1 and 7, and more multinucleated macrophages on days 28 and 90. The authors concluded that short fibres were cleared preferentially and that chrysotile fibres may progressively split into individual fibrils, which can increase fibre numbers in the lung.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.
Comparison of AIA and NIOSH methods on asbestos fibre measurements in the workplace. E. Gonzalez-Fernandez, P.D. de la Osa, F.R. Martín. 1987;31(3):363-73. PubMed · Publisher
Evaluation of the K2 asbestos screening test kit. W. Sahle. 1987;31(2):227-32. PubMed · Publisher
Indoor asbestos levels on a housing estate (determined by transmission electron microscopy). D. Gazzi, G.W. Crockford. 1987;31(4A):429-39. PubMed · Publisher
Inhalation and injection experiments in rats to test the carcinogenicity of MMMF. H. Muhle, F. Pott, B. Bellmann, et al. 1987;31(4B):755-64. PubMed · Publisher

Abstract

In parallel inhalation and intraperitoneal injection (i.p.) experiments with rats, the glass fibre JM 104, Tempstran 475, exemplifying a very thin and durable man-made mineral fibre (MMMF), was compared with crocidolite (South Africa) and chrysotile (California, Calidria RG 144). Aerosol concentrations were 2.2-6 mg m-3. Exposures lasted 1 yr. No significant tumour rate was found in the inhalation test nor from an exposure combination of 100 ppm SO2 and glass fibres. In 74% of the animals exposed to crocidolite bronchiolo-alveolar hyperplasia was detected. Intraperitoneal injection of 0.5 mg of the three different fibre types showed a tumour rate of 17% for glass fibre JM 104, 55% for crocidolite and only 6% for Calidria chrysotile. Calidria chrysotile seems to be much less persistent than other chrysotile samples. The long persistence of JM 104/475 in the lung (half-time of lung clearance about 600 days) and the carcinogenic effects of these fibres after intraperitoneal injection indicate that after inhalation of thin (< 1 µm), long and durable MMMF the suspicion of a carcinogenic potency of these fibres is still well-founded.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Long-term health effects in hamsters and rats exposed chronically to man-made vitreous fibres. D.M. Smith, L.W. Ortiz, R.F. Archuleta, et al. 1987;31(4B):731-54. PubMed · Publisher

Abstract

As part of a comprehensive inhalation study, groups of Osborne-Mendel rats and Syrian golden hamsters were exposed to several types of airborne man-made vitreous fibres (MMVF). Exposure protocols were "nose-only" 6 h per day, 5 days a week for 24 months, with surviving animals maintained for the rest of their lives. Challenge aerosols consisted of four types of fibrous glass, one refractory ceramic fibre (RCF) and one mineral (slag) wool fibre. UICC crocidolite asbestos and clean air served as positive and negative controls for the inhalation groups. Groups of additional controls were unmanipulated caged animals, intraperitoneally (IP) injected animals, and intratracheally (IT) instilled animals. Animals, after their deaths, were examined macroscopically and microscopically. Fibre lung burdens were significant for the inhalation exposures and related to the mean diameters of the fibrous challenge aerosols. The inhalation exposures with MMVF did not result in any adverse effects except for a mesothelioma of the lung in one hamster exposed to the RCF, not a statistically significant finding. Consistent with other reported work, abdominal mesotheliomas were induced in the groups of hamsters and rats injected IP with 0.5-µm mean diameter fibrous glass, RCF and crocidolite asbestos. With IT instillations, primary lung tumours were found only in hamsters and rats receiving UICC crocidolite; no lung tumours occurred in animals instilled IT with two types of MMVF.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Persistence of man-made mineral fibres (MMMF) and asbestos in rat lungs. B. Bellmann, H. Muhle, F. Pott, et al. 1987;31(4B):693-709. PubMed · Publisher

Abstract

In a 2-yr study the persistence of some MMMF, crocidolite and chrysotile in the rat lung was examined after intratracheal instillation. Experiments were based on the assumption that thin, long and durable fibres are of special importance for the carcinogenic potency of these types of substance. Parameters measured included number of fibres, diameter and length distribution of fibres retained in lung ash and leaching of various elements from fibres. The results of the half-time of fibre clearance of the fibre fraction longer than 5 µm has been most important. For a special type of glass microfibre and for ceramic wool, which both had a low alkaline earth content, the half-times of lung clearance were at a level similar to that of crocidolite. For another type of glass microfibre with a high alkaline earth content and a median diameter of about 0.1 µm, a very low half-time was detected. The glass and rock wools studied, which were thicker than the other fibres, had a medium half-time. The acid pretreatment of fibrous material showed that chemical leaching of some alkaline earth and alkali cations increases the in vivo solubility.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Respiratory cancer incidence in Swedish construction workers exposed to man-made mineral fibres and asbestos. G. Engholm, A. Englund, A.C. Fletcher, et al. 1987;31(4B):663-75. PubMed · Publisher

Abstract

The incidence of respiratory cancer has been studied in relation to exposure to man-made mineral fibres (MMMF) within a large cohort of Swedish construction workers. The cohort comprised some 135 000 men, who were all examined by Bygghalsan at regular health check-ups in 1971-1974. The cohort has been followed for mortality through 1983 and for cancer incidence through 1982 by linkage to various national registries. A case-control study within the cohort has been carried out on 518 cases diagnosed as having respiratory cancer. For each case, five controls were selected among those who had not developed such a cancer with individual matching for age and year of first check-up. Subjects selected have been classified into categories based on self-reported exposure and on estimates of average intensity of exposure in occupations concerned. In the analysis smoking habits and density of population in parish of residence were included as potential confounders. Results of an analysis of the incidence of pleural mesothelioma in relation to exposure indicates that subjects in the cohort to some extent are unaware of their exposure to asbestos. The strong association between asbestos exposure and MMMF exposure makes it difficult to separate effects of the two exposures. The results, however, appear compatible with the known effect of asbestos exposure on lung cancer incidence. Subjects classified as heavily exposed to MMMF do not have a significantly higher incidence than unexposed subjects.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The chronic effects of exposure of rats to sized glass fibres. R.T. Drew, M. Kuschner, D.M. Bernstein. 1987;31(4B):711-29. PubMed · Publisher

Abstract

The long-term effects of exposure to sized (1.5 x 5 µm or 1.5 x 60 µm) man-made glass fibres have been investigated. After instillation of a single bolus of fibres, short fibres were observed inside macrophages. In contrast, macrophages could not engulf the long fibres and the macrophages were often seen arrayed along the long fibres. Intratracheal instillation caused formation of large granulomata which often blocked major airways. These granulomata are thought to be artefacts caused by the method of administration. The limited amount of fibres available for the studies (about 10 g of each size range) precluded the use of standard inhalation techniques. Therefore, a transoral inhalation technique was developed that allowed airborne fibres to bypass the turbinates and be inhaled directly into the lung. The resulting fibre deposition pattern of these inhaled fibres was found to be similar to that resulting from the multiple intratracheal instillation of aqueous suspensions of low concentrations of fibres. Having validated the intratracheal instillation technique, the long-term effects of long and short fibres were evaluated. These results were compared with those resulting from repeated instillation of crocidolite asbestos. The principal lesion resulting from exposure to either the long or the short glass fibres was one in which macrophages were found associated with the glass fibres. In contrast, the asbestos caused a marked granulomatous lesion with fibrosis. Neither glass nor crocidolite asbestos caused marked shortening of the lifespan. Neither instilled nor inhaled fibre glass produced tumours in any animals.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Airborne asbestos concentrations in buildings. G.J. Burdett, S.A. Jaffrey. 1986;30(2):185-99. PubMed · Publisher

Abstract

Airborne concentrations of asbestos and other fibres were measured in 39 buildings containing asbestos materials used in their construction or present in warm-air heating systems and in four buildings without asbestos materials. Samples were collected onto membrane filters and analysed using both phase contrast optical microscopy (PCM) and transmission electron microscopy (TEM). Of the 235 samples analysed by PCM, 13% gave fibre concentrations above 0.01 fibres per millilitre (f ml-1); no sample exceeded 0.075 f ml-1. However, subsequent TEM analysis showed that most of the fibres were not asbestos and at only one site did the >5 µm long fibre concentration exceed 0.001 asbestos f ml-1. All sizes of asbestos fibres were also analysed in the TEM at x 17 000 magnification. Only 20% of the buildings had asbestos fibre concentrations above the limit of quantification (>4 fibres counted) and often only a few chrysotile fibrils were detected. Mass calculations based on the fibre size showed that the average concentration of chrysotile was <1 ng m-3 at all sites, and only when large amosite fibres were present was the 1 ng m-3 level exceeded.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Comparison of a fibrous aerosol monitor (FAM) with the membrane filter method for measuring airborne asbestos concentrations. P.J. Iles, T. Shenton-Taylor. 1986;30(1):77-87. PubMed · Publisher

Abstract

An early production model of the Fibrous Aerosol Monitor (FAM; GCA Corporation) has been compared with the membrane filter method, mainly for chrysotile aerosols, in the laboratory and in asbestos cement, friction material and textile manufacturing factories. Correlation in laboratory trials was fairly good, but it was generally too poor in the workplaces studied for the FAM to be considered as a substitute for the membrane filter method. The FAM could be used for detecting concentration changes of a dust cloud of constant composition, but by this criterion it performed little better than a non-discriminating optical particle counter. The unit tested needed maintenance on three occasions in the 18 months of usage and also its correlation with the membrane filter measurements altered over this time.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Comparison of NIOSH and AIA methods for evaluating asbestos fibres: effects of asbestos type, mounting medium, graticule type and counting rules. E. Gonzalez-Fernandez, F.R. Martín. 1986;30(4):397-410. PubMed · Publisher

Abstract

The difficulties of evaluating airborne concentrations of asbestos fibres collected on membrane filters are well known. Factors influencing the measurement include the resolving power of the microscope, the type of mounting medium, the type of graticule and the counting rules for fibres. This paper, firstly, compares the results obtained when counting samples (artificially prepared from aqueous suspensions) of chrysotile, amosite and crocidolite according to the NIOSH and AIA guidelines. These specify different mountants, different graticules and different counting rules. The chrysotile samples were taken from the NIOSH PAT Program; the others were prepared by similar methods. The results showed statistically significant differences between methods for chrysotile and crocidolite but not for amosite nor overall. The mean ratio AIA/NIOSH was about 1.2 for chrysotile and 0.5 for crocidolite. Next, chrysotile only samples were evaluated by NIOSH only counting rules, but using different combinations of three mountants and three graticules. When the data were grouped by mounting medium, both acetone vapour and acetone vapour-triacetin gave higher mean values than the NIOSH mountant by almost 2:1. Grouping by graticule gave mean results in descending order Porton: Walton-Beckett: Patterson in the approximate ratios 1.6:1.2:1 by the SNK-test These findings do not necessarily apply to industrial samples which may contain fibres in different states of dispersion mixed with different types and quantities of non-fibrous particulate.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Fine biogenic silica fibres in sugar cane: a possible hazard. R.H. Newman. 1986;30(3):365-70. PubMed · Publisher

Abstract

Some plants contain structures of biogenic silica which have been implicated as causes of disease in man. Following reports of mesotheliomas and lung cancers in sugar-cane workers, an examination of residues from sugar cane leaf has shown the presence of acicular biogenic silica, 0.85 µm in dia. and 10-300 µm long, which is within the carcinogenic size range for asbestos fibre. It is postulated that the release of such material during the common practice of burning off sugar-cane leaves before harvesting the stems may have health implications for sugar-cane workers.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Variation in fibre and dust counts in an asbestos mine and mill. R.C. Parsons, D.G. Bryant, H.W. Edstrom. 1986;30(1):63-75. PubMed · Publisher
Within-laboratory quality control of asbestos counting. T.L. Ogden, T. Shenton-Taylor, J.W. Cherrie, et al. 1986;30(4):411-25. PubMed · Publisher

Abstract

Internal quality control schemes for asbestos counting are presented for four laboratories handling different sample types and with different organizations and facilities. The purpose is to present these not as perfect models, but as sources of ideas and experience which other laboratories can use in order to plan schemes best suited to their own needs. Common problems which emerge are the determination of reference counts for low-density slides and the handling of the density dependence of counter performance on such slides. One solution is a stock of permanently mounted reference slides, slowly replaced by random selection from routine slides. The reference result can be determined by multiple counting over a period, and the density dependence can be allowed for by using OGDEN'S method [OGDEN (1982) Health and Safety Executive Research Paper, No. 18. ISBN 0 7176 0101 3] of expressing deviations as multiples of a calculated 'expected standard deviation'. A link to the national mean can be provided through the Regular Inter-laboratory Counting Exchange (RICE) inter-laboratory quality control scheme.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Asbestos and other fibre levels in buildings. S. Altree-Williams, J.S. Preston. 1985;29(3):357-63. PubMed · Publisher
Rate of decline of asbestos fibre concentrations in room air. J. Prentice. 1985;29(3):439-40. Letter PubMed · Publisher
Relationship of mortality to measures of environmental asbestos pollution in an asbestos textile factory. J. Peto, R. Doll, C. Hermon, et al. 1985;29(3):305-55. PubMed · Publisher
Reproducibility of dust disturbance techniques during clearance sampling after asbestos removal. J. Prentice, B. Gonsalves. 1985;29(3):435-7. PubMed · Publisher
The assessment of a modification to the acetone/triacetin clearing technique as used in the measurement of airborne asbestos dust. I.W. Furness, P.J. Reed. 1985;29(1):109-12. PubMed · Publisher
Use of a cowl in asbestos air sampling. K.L. Knight, D.M. Bloor, F. Miller. 1985;29(2):289-91. Letter PubMed · Publisher

Summary

This letter reported a comparison of cowled and uncowled filter holders for personal asbestos air sampling. The European Reference Method (ERM) required an open-face filter holder fitted with an electrically conductive cylindrical cowl. The authors noted that little work had compared it with earlier uncowled designs, and that Speight and Marsh had reported a substantial difference when sampling amosite insulation fibres. In an asbestos cement factory, cowled and plastic non-cowled holders were mounted side by side on the shoulder of a man transferring baled chrysotile asbestos into a rod mill. Samples were taken concurrently with identical backing plates and orientation, inner and outer positions were alternated, and counters did not know the holder type or position. Sampling periods were varied to give fibre densities of around 100-500 fibres per mm2, and flow rates were measured at the start, middle and end. Filters were prepared and counted by the ERM, with repeated counts. Of 20 samples, one was lost, and nine pairs of standardized fibre densities were analysed. A paired Student's t-test (t = 0.0238; tabular t 2.306 for 8 degrees of freedom) showed no significant difference at the 5% level. An F-test (F = 1.16; tabular F 4.43) showed no significant difference in variances. The authors concluded that, for airborne chrysotile, cowled holders made no practical difference to results. This differed from Speight and Marsh's experience with amosite.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
A comparison of light microscopy and transmission electron microscopy results in the evaluation of the occupational exposure to airborne chrysotile fibres. A. Marconi, E. Menichini, L. Paoletti. 1984;28(3):321-31. PubMed · Publisher

Abstract

A comparison has been made between light microscope (LM) and transmission electron microscope (TEM) counts of airborne chrysotile fibres, collected on 30 membrane filters from different working processes. For TEM counts, fibres of length l > 5 µm were classified according to diameter d, namely 0.3 µm < d < 3 µm (microscopic fibres) and d ≤ 0.3 µm (submicroscopic fibres); short fibres, l ≤ 5 µm, were taken into account separately. A very good correlation has been found between LM and TEM counts, both for microscopic and total (microscopic + submicroscopic, l > 5 µm) fibres, for densities 40-500 fibres mm-2. The median of the ratios between TEM and LM counts has been found to be 1.1 for microscopic fibres and 1.2 for total fibres. From TEM counts, submicroscopic fibres have been found to account for about 10% of total l > 5 µm fibres. The mean ratio between short fibres and those with l > 5 µm was in the range 0.8-3.6, depending on the working process. These results suggest the possibility of adopting factors, varying with the kind of working process, to be applied to LM counts in order to estimate the exposure to all the asbestos fibres considered important for a comprehensive evaluation of the risk.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Asbestos fibre counting by image analysis--the performance of the Manchester Asbestos Program on Magiscan. L.C. Kenny. 1984;28(4):401-15. PubMed · Publisher

Abstract

Manchester University's Asbestos fibre-counting Program (MAP) now performs satisfactorily on the Magiscan image-analyser for most industrial samples. Further work to develop the software is unlikely to produce proportionate improvement in performance. From the available data, MAP counts are not distinguishable within the range of results from visual-counting laboratories either internationally, when using the European Reference Method (ERM), or nationally, using in-house methods or the ERM. When compared with those visual counters employed by the Health and Safety Executive (HSE) who are trained and practised in the ERM, MAP results are not distinguishable at concentrations above approximately 0.3 fibres ml-1. MAP counts relatively high at concentrations below 0.3 fibres ml-1, but is still within the confidence limits established from quality control with HSE's in-house method. MAP performance on routine samples taken after delagging operations has not yet been investigated fully. HSE are now using the MAP in conjunction with Magiscan for routine monitoring of asbestos concentrations, taking these factors into account.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Determination of mineral fibre in human lung tissue by light microscopy and transmission electron microscopy. A.J. Rogers. 1984;28(1):1-12. PubMed · Publisher

Abstract

Mineral fibre residues found in the lung provide an indication of past exposure and an important pointer as to whether disease is asbestos-related. A method is presented based on chemical digestion of the lung tissue, deposition of the mineral fraction of the digest on membrane filters followed by suitable preparation of the filters for either light microscopy or transmission electron microscopy examination. Results on the variability of fibre concentration with deposition site in the lung are included together with information on the precision of the method of estimation. This information provides the basis of interpretation for individual cases and for observations of trends in population studies. Results from a survey of fibre concentration in lungs from mesothelioma cases are compared with those obtained from a sample of the Australian male population.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Mass concentrations of airborne asbestos in the non-occupational environment--a preliminary report of U.K. measurements. G.J. Burdett, J.M. le Guen, A.P. Rood. 1984;28(1):31-8. PubMed · Publisher

Abstract

Airborne asbestos mass concentrations were measured at a number of sites by taking high-volume electrostatic precipitator samples and analysing by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD was shown to overestimate chrysotile levels owing to interference by non-fibrous analogues. The sites sampled included two asbestos waste tips, the immediate environments of two asbestos products factories, a decontamination site and a busy urban road junction, as well as rural and urban background. Levels appreciably above the background were recorded at industrial sites.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Quality control of airborne asbestos fibre counts in the United Kingdom--the present position. N.P. Crawford, A.J. Cowie. 1984;28(4):391-8. PubMed · Publisher

Abstract

The United Kingdom Central Reference Scheme for asbestos counting has been expanded by initiating a series of regular interlaboratory counting exchanges (RICE) to minimize national within- and between-laboratory differences in asbestos fibre counts obtained by the membrane filter method. The scope of the present RICE operation is described and results are presented depicting current interlaboratory differences. National scatter is unacceptably large; up to ten-fold systematic differences occur between visual-counting laboratories, whilst random differences in counts of up to 100-fold occur on the same sample. For the reference samples evaluated, counts made by Magiscan automated image analysers are generally near the national mean and differences between Magiscans are usually small compared with differences between visual-counting laboratories. Results obtained by an experienced group of laboratories relative to Magiscan have been used to derive a categorization procedure for assessing laboratory performance. Some details are given concerning future operation of RICE with a view to improving national reproducibility. A European-based scheme similar to RICE is needed to help ensure that the community asbestos directive applies uniformly in CEC countries.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Rate of decline of asbestos fibre concentration in room air. J.S. Moorcroft, M.J. Duggan. 1984;28(4):453-7. PubMed · Publisher

Abstract

Asbestos fibres may be lost from room air by several mechanisms including gravitational settling, ventilation and attachment to surfaces. The results of some measurements of airborne fibre concentrations obtained during monitoring after the removal of sprayed asbestos ceilings are presented. Some indication is given of the rate at which the concentration of fibres decreases after their having been raised by the disturbance of surface dust. Some theoretical estimates of the losses due to settling and ventilation suggest that these two mechanisms are not sufficient to account for the observed results and that some additional mechanism, possibly attachment to room surfaces, is operative.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Size distributions of occupational airborne asbestos textile fibres as determined by transmission electron microscopy. A.P. Rood, R.R. Streeter. 1984;28(3):333-9. PubMed · Publisher

Abstract

The size distributions of airborne chrysotile fibres, associated with the processes of carding, spinning and weaving in an asbestos textile factory, have been evaluated by transmission electron microscopy. The distributions were approximately log-normal, with little change between processes. Median lengths and diameters were 1.6 and 0.08 µm, respectively. The results indicate that about 60% of fibres would not be seen by scanning electron microscopy, under the usual conditions, and an even larger proportion would be missed by optical microscopy. For fibres longer than 5 µm, then, about 70% of fibres would be seen by the scanning electron microscope. An optical microscope with a resolution of 0.5 µm would see approximately one quarter of all fibres greater than this length.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Solubility of rockwool fibres in vivo and the formation of pseudo-asbestos bodies. A. Morgan, A. Holmes. 1984;28(3):307-14. PubMed · Publisher

Abstract

Sized rockwool fibres were administered to rats by intratracheal instillation to study their solubility in the lung, and also to hamsters to study the formation of pseudo-asbestos bodies. Rats were killed serially and the fibres recovered by digesting lungs with hypochlorite solution. Count median diameters (CMDs) of the recovered fibres were measured at their centres with the light microscope and, after 18 months, there was no significant change in CMD. Even after six months, however, it was apparent that fibres were becoming thinner at their ends than in the middle so that slow dissolution does occur. The formation of pseudo-asbestos bodies on rockwool fibres in the hamster lung followed a similar time course to that for anthophyllite asbestos and glass fibres.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Statistical uncertainties in asbestos-laboratory classification through the RICE scheme. T.L. Ogden. 1984;28(4):449-52. PubMed · Publisher
Formation of pseudo-asbestos bodies on sized glass fibres in the hamster lung. A. Holmes, A. Morgan, W. Davison. 1983;27(3):301-13. PubMed · Publisher

Abstract

Sized glass fibres, 3 µm in diameter and with lengths ranging from 10 to 100 µm, were administered to hamsters by intratracheal instillation. Animals were killed serially and fibres extracted from their lungs by hypochlorite digestion. Determinations were made of fibre dimensions with the light microscope and whether they were uncoated, partially or fully coated. As shown in previous studies with rats, the longer fibres dissolved more rapidly than the short, but all fibres dissolved more rapidly in the hamster than in the rat lung. Partially coated fibres were detected after 1 month for the 60 and 100µm and after 2 months for the 10 and 30 µm. There were wide variations in the frequency of coated fibres in different animals killed at the same time, but it tended to increase up to 5 months and then to decline. It was clear that the coating of glass fibres did not prevent their dissolution.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Measurement of fibre diameter from SEM images. C. Tillman. 1983;27(1):113-5. Letter PubMed · Publisher
Relationships between simultaneous airborne dust samples taken with five types of instruments at South African asbestos mines and mills. R.S. Du Toit, L.W. Isserow, T.C. Gilfillan, et al. 1983;27(4):373-87. PubMed · Publisher

Abstract

Simultaneous airborne dust samples were taken with five types of instrument, namely, konimeter, thermal precipitator, membrane filter, tyndallometer and VC 25 gravimetric sampler, on the surface and underground at two types of asbestos mine, producing amosite and Cape crocidolite respectively. The results were analysed and compared in terms of five different concentration parameters, namely, particles plus short fibres (p+sf), long fibres (lf), particles plus short fibres plus long fibres (p+sf+lf), the volume (tyndallometer readings) and the mass of dust (VC 25). The Kolmogorov-Smirnov statistic was used to test for normality and the Bartlett statistic for equality of variance of the transformed concentration data recorded by each type of instrument.

Fourteen linear relationships were investigated. In those cases where replicates were given these were used to obtain estimates of the error variances for the predictor and the response variables. With these estimates an additional regression equation to the least squares equation was determined. This new equation is recommended in preference to the corresponding least squares equation, as it is based on information which is discarded when only the position means are used.

All but one of the fourteen relationships reached statistical significance.

The konimeter and the thermal precipitator can be linked with the membrane filter, the tyndallometer can reveal short time variations in the fibre level and the VC 25 can disclose the asbestos content of the fine dust.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Vickers instruments M88 rapid asbestos fibre monitor. K.J. Verrill. 1983;27(1):111-2. Letter PubMed · Publisher
Void-counting in assessing membrane filter samples of asbestos fibre. M.D. Attfield, S.T. Beckett. 1983;27(3):273-82. PubMed · Publisher
A procedure for the estimation of asbestos collected on membrane filters using transmission electron microscopy (TEM). A.P. Middleton, E.A. Jackson. 1982;25(4):381-91. PubMed · Publisher
Analysis of airborne dust samples for chrysotile by X-ray diffraction: interference by non-asbestiform serpentine. A.P. Middleton. 1982;25(4):443-7. PubMed · Publisher
Industrial trials with the Vickers M88 rapid asbestos fibre counter. A.D. Jones, R.W. Gale. 1982;25(1):39-51. PubMed · Publisher
The influence of external aerodymanic factors on the measurement of the airborne concentration of asbestos fibres by the membrane filter method. A.M. Johnston, A.D. Jones, J.H. Vincent. 1982;25(3):309-16. PubMed · Publisher

Abstract

This paper describes experiments carried out in the laboratory to clarify interpretation of the role of sampling flow rate and wind speed on the efficiency of sampling airborne asbestos fibres in workplaces. The experiments were carried out with test clouds of UICC amosite and UICC chrysotile with aerodynamic characteristics sufficiently close to those of workplace dusts to allow direct comparison to be made, at least as far as the immediate aims of this enquiry are concerned. It was shown unambiguously, for conditions of practical interest, that there were no significant effects of sampling flow rate and wind speed on the measurement of fibre mass concentration and fibre number concentration respectively. Thus, any observed bias in the measurement of fibre concentration by manual counting must instead be attributable to psychological effects relating to the density of fibres on the filter. On the basis of these results, it is suggested that recommended procedures which impose limitations on sampling flow rate or face velocity are unnecessarily restrictive. Rather it is preferable to tighten up the prescribed limits on fibre density on the filter.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The nature, hazards and assessment of occupational exposure to airborne asbestos dust: a review. W.H. Walton. 1982;25(2):117-247. Review PubMed · Publisher

Abstract

Hygiene measurement parameters for airborne asbestos are discussed from mineralogical and biological standpoints. It is concluded that at present there is no practicable alternative to the membrane filter/phase contrast optical microscope (MF/OM) method for routine use, despite its many limitations, but that some features, including the fibre size limits, should be revised.

On present evidence fibre counts appear to provide a better index of hazard than respirable mass concentration. Considerations of respirability and biological activity together suggest that the counts should be of fibres in the size range: length greater than 5-10 µm but less than 100 µm; width less than 1.5-2 µm (no minimum specified); aspect ratio greater than 5:1 to 10:1. Compared with present definitions (l>5 µm, d<3 µm, l/d>3:1) this reduces the maximum diameter and increases the minimum aspect ratio.

The main drawback of the MF/OM method is that fibres thinner than ca. 0.4-0.2 µm (depending on the microscope, method of mounting the sample and the observer's visual acuity) cannot be seen, although they contribute substantially to the number to an extent that varies with asbestos variety. This makes standardization of the method extremely difficult and is the main reason why different hygiene standards are needed for different asbestos varieties, especially between the amphiboles crocidolite and amosite. Further studies of the lung deposition of fibres thinner than 0.1-0.2 µm are needed.

In animal experiments chrysotile has generally been more damaging than the amphiboles, in contrast to human epidemiological experience. This is probably due to the lesser durability of chrysotile when retained in the body over long periods, as evidenced by the surprisingly small amounts of chrysotile compared with amphibole found in human lungs at autopsy despite the much greater industrial usage of chrysotile.

Many non-asbestiform amphiboles and other minerals give rise to elongated dust particles of aspect ratio>3:1. Discrimination between these and true asbestos particles is extremely difficult in individual cases, although overall size distributions differ. Recent codes for the MF/OM method indicate that discrimination is not to be attempted, but present practice in the U.K. is variable with marked effect on counting levels. Increasing the aspect ratio limit to >5:1 or preferably >10:1 would exclude many of the non-asbestiform particles but have relatively little effect on the true asbestos count. This supplements the biological evidence for a change from the present aspect ratio limit of 3:1 which was arbitrarily chosen by the ARC in 1958.

Another problem for which there is little scientific guidance is the evaluation of clumps and other entities. The use of aerodynamic size selectors in sampling together with an upper size limit of length+width <100 µm for 'thistle-down' particles should help. Other technical changes to the MF/OM method are suggested.

The novel suggestion is made that total fibre length per unit volume (m/m3) might reflect the hazard of asbestos exposure better than fibre number concentration and be easier to assess by man or machine—by counting crossing-points between fibres and a line drawn across the sample.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Visibility of fine fibres of asbestos during routine electron microscopical analysis. A.P. Middleton. 1982;25(1):53-62. PubMed · Publisher

Abstract

Most analyses for asbestos in samples from the non-occupational environment are carried out using techniques based upon either scanning (SEM) or transmission (TEM) electron microscopy. The mode of image formation and resolution obtainable differ between SEM and TEM and the present study was undertaken in order to provide some indication of the comparability of observations made by the two techniques, with particular reference to the visibility of fine, sub-micrometre fibres. The results indicate that, in general, at a given magnification finer fibres are visible when using TEM than when using SEM. When using SEM, fibre visibility is improved by the use of higher magnifications, by the use of slower raster speeds and by the use of gold rather than carbon for specimen coating. The use of photomicrographs leads to improved fibre visibility in both SEM and TEM images. The study suggests that comparable results can probably be obtained from the two techniques, although fibres ≲0.1 µm dia may be close to the limit of visibility in the SEM. In order to facilitate inter-laboratory comparison of results it would seem appropriate for standard samples to be available so that optimum conditions can be determined for the observation of fine fibres.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Asbestos concentrations in public buildings - a preliminary report. J.M. le Guen, G. Burdett. 1981;24(2):185-9. PubMed · Publisher

Abstract

Airborne asbestos concentrations were measured by a variety of sampling and analytical techniques, in 4 schools, 2 other educational establishments, 5 houses, a theatre and a television studio, in all of which asbestos-containing construction materials had been used. At some sites these materials had been damaged to expose visible fibres, but in no case did airborne asbestos concentrations exceed 10-8 g/m3 roughly 0.02 % of the occupational hygiene standard for chrysotile, or 10-9 g/m3 in the three cases where the TEM was used.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Clearing and mounting techniques for the evaluation of asbestos fibres by the membrane filter method. J.M. Le Guen, S. Galvin. 1981;24(3):273-80. PubMed · Publisher

Abstract

This paper describes three clearing and mounting techniques used in the evaluation of fibres by the membrane filter method and puts forward new methods for clearing membrane filters made of mixed esters of cellulose. The paper also sets out criteria for assessing the relative merits of clearing and mounting techniques and shows that, judged by these criteria, one of the new methods offers considerable advantages over the other methods described.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
In situ identification of asbestos fibres collected on membrane filters for counting. N.P. Vaughan, S.J. Rooker, J.M. Le Guen. 1981;24(3):281-90. PubMed · Publisher
Results of an asbestos counting trial performed in France in 1979. B. Carton, E. Kauffer, G. Derzko, et al. 1981;24(1):9-21. PubMed · Publisher

Abstract

In France a law has been introduced giving a time-weighted average of the concentration of asbestos at the work place. This paper reports a large-scale comparison trial organized by INRS between the counting operators in 1979. Forty-seven operators participated in this trial and 102 mounted slides were used coming from different industrial samplings. In total more than 1000 counts were performed. Two methods of evaluating these results are presented: a comparison of the mean without any assumption on the standard deviation of the counts (Welch test), and a method using a limit value. These two methods agree very well and point to a group of operators whose response can be relied upon.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The biological effects of mineral fibres. J.M. Davis. 1981;24(2):227-34. Review PubMed · Publisher

Abstract

The history of asbestos-related disease and the results of research into the ways in which asbestos fibres are able to damage tissue are reviewed. Although crocidolite has been accepted as constituting a particularly great hazard and is subject to a more stringent hygiene standard that has effectively terminated its use in the U.K., experimental studies on animals have not proved it to be more carcinogenic than chrysotile. It is possible that rats react differently from humans, but more likely possibilities are that in past industrial usage crocidolite produced higher dust concentrations than amosite or chrysotile and that chrysotile is less durable than crocidolite in the lungs over the 10-20 yr that tumour induction takes in man. Other mineral fibres, both natural and man-made, have come under study and there is some evidence from laboratory experiments that they may produce similar effects to asbestos if of comparable size. The position for man-made insulation fibres appears relatively good and the results of studies of human populations exposed to glass fibre have so far been negative. While not all mineral fibres may constitute a health hazard if used industrially, there is enough evidence of potential harm to indicate that all new types of fibre should be subjected to careful testing.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The dimensions of airborne asbestos fibres--I. Crocidolite from Kuruman area, Cape Province, South Africa. C.Y. Hwang, G.W. Gibbs. 1981;24(1):23-41. PubMed · Publisher

Abstract

The dimensions of airborne fibres collected at an underground mine and two mills producing crocidolite in the Kuruman area of Cape Province, South Africa, and of those collected at a plant manufacturing pipes in South Africa using Cape crocidolite and chrysotile asbestos are reported. The measurements were made using a transmission electron microscope, a scanning electron microscope and a light optical microscope. There was no apparent change in diameter with stage of processing although in certain processes, such as cutting asbestos cement pipe, the presence of chrysotile fibres altered the size distribution markedly. However, there was some change in length with stage of processing. The finding that the observed diameter distributions in airborne samples in this study are similar to those previously reported in the lungs of workers exposed to Cape crocidolite may indicate that, if diameter is the important parameter in relation to health effects, the hazard associated with exposure to Cape crocidolite should, dose for dose, be similar for all stages of processing. The proportion of long fibres in the air has been found to be very small and observations on very large numbers of fibres are necessary to confirm their presence.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
A routine for the control of the performance of microscopists evaluating airborne asbestos fibre samples on membrane filters by phase contrast microscopy. J.R. Hoyes, R. Clayton. 1980;23(4):381-401. PubMed · Publisher

Abstract

By the use of slide circulations within a laboratory with slides of sufficient density to keep the Poisson error low and re-instruction as required, the relative performance of a team of membrane filter counters has been controlled such that 88 % of results obtained for performance checking purposes were within ±30% of the laboratory mean over the period November 1977-March 1980. Analysis of the results obtained indicates that the inherent standard deviation of the results from a counter is typically 16%. The slides circulated were prepared by the acetone-triacetin mounting method. There is no conclusive evidence from the data presented that during the period mentioned the slides have deteriorated.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Is there a risk to health in using asbestos--cement pipes for the carriage of drinking water?. S.F. McCullagh. 1980;23(2):189-93. PubMed · Publisher
The effects of sampling practice on the measured concentration of airborne asbestos. S.T. Beckett. 1980;23(3):259-72. PubMed · Publisher

Abstract

The effect of variations in sampling practice upon the measurement of airborne amosite and chrysotile asbestos fibre concentrations by the membrane filter method has been investigated experimentally in a laboratory dust chamber and to a lesser extent in industrial situations. The parameters tested were sampling flow rate and volume, the pore size and electrostatic charge of the filter and the angle of inclination of the sampling head. For all types of filter an increase in the sampled volume resulted in a relative lowering of the measured concentration. This was found to be due to an analytical effect and not to changes in sampling efficiency of the filter. The collection of fibres without a sampling flow accounted for 10% of a sample taken at 200 ml min⁻¹. This effect is therefore only relatively important at very low flow rate. Large (8 µm) pore size membrane filters, when sampling amosite at 2 1. min"', produced a fibre count approximately 15% lower than equivalent measurements on 0.8 µm pore sized filters, although there was no significant fibre penetration completely through this type of filter. Approximately 20% of both amphibole and chrysotile fibres, however, passed through an 8 µm pore size Nuclepore filter at this sampling rate. The electrostatic charge on the filter and the angle of inclination of the sampling head did not appear to significantly affect the measurements.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

1970s

A study of the size distributions of airborne amosite fibres in the manufacture of asbestos insulation boards. S.T. Beckett, J.L. Jarvis. 1979;22(3):273-84. PubMed · Publisher

Abstract

A comparison has been made of the size distributions of airborne fibres at different locations in two major manufacturing plants using amosite asbestos. Side-by-side samples were taken on membrane and Nuclepore filters; the membrane filters were examined using optical phase microscopy and the length distributions of fibres longer than 5 µm measured. The Nuclepore filter samples were examined using scanning electron microscopy and the lengths of fibres greater than 0.6 µm with diameters of more than 0.2 µm were determined. No major differences were found in size distribution either at the different sites or due to the analytical technique used, except for samples taken in relatively high velocity air streams. The effect of a change from the present standard in length or aspect ratio of the fibres counted on the measured concentration is discussed.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Conversion of the asbestos fibre concentration recorded by means of the konimeter and the thermal precipitator to that expected by means of the membrane filter method. R.S. du Toit, T.C. Gilfillan. 1979;22(1):67-83. PubMed · Publisher

Abstract

Previously published relationships between asbestos fibre concentrations recorded by means of the Konimeter, the TP and with membrane filters are re-presented in a more convenient form to facilitate conversion of Konimeter and TP data to membrane filter equivalents.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Further observations on the short-term retention and clearance of asbestos by rats, using UICC reference samples. A.P. Middleton, S.T. Beckett, J.M. Davis. 1979;22(2):141-52. PubMed · Publisher

Abstract

Rats exposed to UICC chrysotile 'A', amosite and crocidolite at concentrations close to 1, 5 and 10 mg/m3 of respirable fibre for a total of 210 h over a 6-week period were killed in five groups at approximately monthly intervals. The asbestos retained in the lungs was estimated by infra-red spectrophotometry after ashing. The results indicated different initial fractional retentions but that the rate of clearance was independent of the type of asbestos and of the concentration during exposure. The rates of deposition and clearance could be described in terms of a model, modified from that published by MORGAN et al. (1977). In this model it is assumed that a fraction K, of the estimated aggregate dose is deposited in three 'compartments', from which asbestos is subsequently cleared with half-times of 0.38, 8 and 118 days. It is also assumed that asbestos enters the three 'compartments' in the proportions 86.5:5.3:8.2, respectively. The fractional deposition, K, of chrysotile was much less than for the two amphiboles but increased with diminishing concentration, from 0.17 at ca. 10 mg/m3 to 0.36 at ca. 1 mg/m3. The K-value for amosite, 0.65, was less than for crocidolite, 1.0, both being independent of concentration. In view of the nocturnal nature of rats it was thought that the normal practice of dust exposure during daylight, a period of reduced activity, might have led to misleading results. Two further experiments were therefore carried out in which rats were exposed to UICC chrysotile 'A' and crocidolite in a darkened chamber to simulate nocturnal conditions. The rates of clearance were closely similar to those observed after daylight exposure. Application of the model described above indicated that, although the fraction of crocidolite deposited was comparable with that observed after daylight exposure, the fraction of chrysotile deposited was approximately three times that deposited during the comparable daylight experiment. Possible reasons for the different retention pattern of chrysotile are discussed.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Procedure for the detection and identification of asbestos and other fibres in fibrous inorganic materials. L.J. Monkman. 1979;22(2):127-39. PubMed · Publisher

Abstract

A systematic procedure for the detection and identification of asbestos and other fibres in insulation and other fibrous materials is described. The need for adequate sampling and acid pre-treatment to remove the bulk of the non-fibrous matrix of such samples is stressed. The method requires an initial low-power stereo-microscopic examination followed by petrological polarization microscopic identification of the fibres. The optical characteristics required for the unambiguous identification of the common asbestos minerals are given.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Quantitative assessment of inorganic fibrous particulates in dust samples with an analytical transmission electron microscope. F.D. Pooley, N.J. Clark. 1979;22(3):253-71. PubMed · Publisher

Abstract

With the aid of an analytical transmission electron microscope it is possible to quantify by number and mass the various inorganic fibrous particulate phases that may occur in dust samples. Discrimination between fibres of various mineral types can be made by reference to their individual chemical compositions and number concentrations on filter preparations determined with a reasonable accuracy. Mass estimates can be obtained by sizing the length and diameter of the various individual fibrous particles, these dimensions then being used to calculate the mean fibre volume of individual fibrous phases which, in conjunction with a specific gravity value, a correction factor for fibre shape and number concentration data, can be used to calculate the weight of any particular mineral phase on a filter preparation. Careful standardization of the quantitative procedure should be performed before establishing a routine.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The analysis of lagging materials for asbestos: CEGB procedures. D.L. Ward. 1979;22(3):319-23. PubMed · Publisher
On the occurrence of fibres of calcium sulphate resembling amphibole asbestos in samples taken for the evaluation of airborne asbestos. A.P. Middleton. 1978;21(1):91-4. PubMed · Publisher

Summary

The author reported an observation made while measuring airborne asbestos with the membrane filter method, in which fibres on cleared filters are counted by phase contrast microscopy. Some laboratories reported total fibre counts and others reported asbestos fibres only, although no guidance was given on how to tell asbestos from other fibres. In a survey of airborne asbestos during the removal of asbestos lagging from steel roof panels in a prefabricated building, airborne dust was collected on membrane filters. The lagging was mostly chrysotile with a trace of crocidolite. Side-by-side samples were taken on Nuclepore filters for scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDXA). Phase contrast counts indicated significant concentrations of airborne asbestos, and almost all fibres had the needle-like shape typical of amphibole asbestos. In the SEM, many fibres still resembled amphibole asbestos. However, EDXA showed that their major elements were calcium and sulphur rather than silicon and iron, so they were presumably calcium sulphate, probably from plaster board disturbed during the work. The author concluded that mistaking non-asbestos fibres for asbestos in routine counting can considerably overestimate airborne asbestos, and suggested taking side-by-side samples for evaluation by another method such as SEM/EDXA. The author also noted that if fibre size rather than chemistry governs disease risk, all fine fibres might be counted, and expensive electron microscopy might not necessarily be justified.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
The counting of small numbers of asbestos fibres on membrane filters: a comparison of results from some commercial laboratories. M.J. Duggan, E.W. Culley. 1978;21(1):85-9. PubMed · Publisher
The routine monitoring of airborne asbestos in an occupational environment. A.L. Rickards. 1978;21(3):315-22. PubMed · Publisher
A preliminary survey of the hazards to operators engaged in the disposal of asbestos waste. J.S. Kinsey, R.C. Keen, C.J. Mumford. 1977;20(1):85-9. PubMed · Publisher
A summary of asbestos fibre counting experience in seven countries. G.W. Gibbs, P. Baron, S.T. Beckett, et al. 1977;20(4):321-32. PubMed · Publisher

Abstract

The membrane filter method for the evaluation of airborne concentrations of asbestos in the work place, is now used in many countries. In order to ensure uniform protection for the worker and internationally comparable exposure data it is important that different laboratories can reproduce fibre counts with reasonable accuracy. The results of an international counting trial of fibre by centres in nine countries were published recently in this journal. This current report summarises the results of internal exchanges of membrane filters for asbestos counting in seven of these countries. Observations from these several countries indicate the need for regular comparisons of counts between laboratories, regular contact with experienced observers, proper training in the use of the phase contrast microscope, standardisation of the methods of counting agglomerates, attention to the types of samples used for internal and external comparisons, choice of microscope, and separate training for counting chrysotile and amphibole fibres. An improved method of producing standard asbestos samples for counting purposes is required.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Health aspects of man-made mineral fibres. A review. J.W. Hill. 1977;20(2):161-73. Review PubMed · Publisher

Abstract

Man-made mineral fibres (MMMF) have been in production for over 40 years. The diameter of the fibres has in general been too large to cause a high concentration of respirable fibrous dust during manufacturing or use. Medical studies in several countries of groups of workers exposed for lengthy periods to glass fibre have produced evidence of the absence of lung fibrosis or respiratory impairment, and have not shown an excess risk of lung or other cancers. Reports of a few individuals with respiratory disease and an exposure to MMMF have not clearly indicated the fibres as a cause of the disease. Limited pathological studies of lungs of workers with long term exposures to glass fibre have shown no evidence of lung damage. Animal inhalation studies in general confirm that MMMF are not fibrogenic. Following injection of fibres into the pleura, the incidence of tumours produced is related to the dose, diameter and length of the fibres. Further research is needed to enlarge the number and diversity of the epidemiological studies; also to look more critically at the biological effects of small diameter fibres which may arise as a result of changes in technology of production and use of MMMF.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Penetration of overall hoods by water-borne crocidolite fibres. R. Goode, T. Waldron. 1977;20(2):195-6. Letter PubMed · Publisher
Review of early results of comparative tests with the konimeter and the thermal precipitator in asbestos mines. R.S. Du Toit. 1977;20(3):279-81. PubMed · Publisher
Simultaneous airborne dust samples with konimeter, thermal precipitator and dosimeter in asbestos mines. R.S. du Toit, T.C. Gilfillan. 1977;20(4):333-44. PubMed · Publisher

Abstract

Simultaneous airborne dust samples were taken with three types of instruments: konimeter, thermal precipitator and dosimeter (personal sampler with membrane filter) in eight asbestos mines producing four types of asbestos (Cape crocidolite, Transvaal crocidolite, amosite and chrysotile). Additional tests were carried out in a dust duct with a specific type of asbestos fibre at a steady dust concentration. The filtering efficiencies of 8 and 0.8 µm pore size membrane filters used in the dosimeter were compared. The statistical analyses of the results have been summarised and formulae are given to convert the fibre concentrations recorded by the konimeter and the thermal precipitator into that expected with the membrane filter method of sampling.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
A comparison of airborne asbestos fibre counting with and without an eyepiece graticule. S.T. Beckett, R.K. Hey, R. Hirst, et al. 1976;19(1):69-76. PubMed · Publisher

Abstract

Previous results have shown that when asbestos fibres on membrane filters are counted over the whole field of view of the microscope, lower concentration values are obtained than when the counting is confined to a central graticule grid area. Further studies have been carried out to verify this grid effect, to determine its magnitude for amosite and chrysotile asbestos fibres, and to ascertain its causes. The effects of various physical and human factors were investigated. With small graticule grids, fibre counts were increased by a factor of about 1.5 for amosite and 2.5 for chrysotile as compared with full-field counting. The effect was attributed mainly to human errors associated with full-field counting. It was concluded that more reliable and accurate counts are obtained in the routine evaluation of airborne asbestos dust concentrations by using an eyepiece graticule method of counting than by the full field method. It is therefore recommended that this method of counting be adopted and that steps be taken to reach national or, preferably, international agreement on a standard grid counting procedure.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
A simple small light-weight personal dust sampling unit for full shift determination of asbestos dust exposure. J.W. Winters. 1976;19(1):77-80. PubMed · Publisher
Health hazards of thermal insulation products. D.C. Muir. 1976;19(2):139-45. PubMed · Publisher
The short-term effects of chronic asbestos ingestion in rats. R.E. Bolton, J.M. Davis. 1976;19(2):121-8. PubMed · Publisher
Alignment of respirable asbestos fibres by magnetic fields. V. Timbrell. 1975;18(4):299-311. PubMed · Publisher
Fibre release from asbestos garments. G.W. Gibbs. 1975;18(2):143-9. PubMed · Publisher
Monitoring an asbestos spray process. J.W. Skidmore, J.S. Jones. 1975;18(2):151-6. PubMed · Publisher
The descent angle of inclined cylinders--a possible means of separating fibres by length. T.L. Ogden, W.H. Walton. 1975;18(2):157-60. PubMed · Publisher
The generation and evaluation of UICC asbestos clouds in animal exposure chambers. S.T. Beckett. 1975;18(3):187-98. PubMed · Publisher

Abstract

When carrying out animal inhalation experiments using UICC asbestos it was found necessary to modify the dust cloud generation technique described by Timbrell, to obtain a stable, well-dispersed cloud at concentrations from 1 to 10 mg/m³. The MRE gravimetric dust sampler type 113 A recommended by Timbrell as a routine monitoring instrument, was found to undersample at high chrysotile concentrations, and an alternative system was developed using a vertical elutriator. Fibre number counts of the clouds were obtained and correlated with mass concentrations. A Royco particle counter model 225 and Sibata digital dust indicator model AP.3 were tested, and their usefulness at the prevailing high concentrations assessed. Fibre length distributions for clouds of UICC chrysotile A, amosite and crocidolite asbestos are reported.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The identification of asbestos dust with an electron microscope microprobe analyser. F.D. Pooley. 1975;18(3):181-6. PubMed · Publisher

Abstract

It is possible with the aid of a transmission electron microscope fitted with suitable X-ray analytical equipment, to identify submicroscopic particles of the various asbestos minerals. Identification of particles should depend upon the production of accurate chemical data and not upon spectrum morphology. Suitable pure mineral powders of known chemistry can be used as standards to calibrate equipment and the calibration used to obtain the chemistry of unknown particles for a positive identification. The transmission E.M. fitted with energy dispersive X-ray analytical equipment is more versatile than other combinations of electron optical machines and X-ray analytical equipment. This is due to the more versatile operating characteristics of the transmission E.M. and the ability to display the X-ray spectra obtained from a particle with an energy dispersive analysis system, thus showing the presence of all the major elements with higher atomic numbers than sodium 11.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The use of infrared spectrophotometry for the estimation of small quantities of single varieties of U.I.C.C. asbestos. S.T. Beckett, A.P. Middleton, J. Dodgson. 1975;18(4):313-20. PubMed · Publisher

Abstract

An i.r. technique has been developed to measure small quantities (down to less than 10 ng) of single varieties of asbestos. This has been used to monitor airborne fibre concentration and to measure the asbestos recovered from the lungs of rats. The method has the advantages that it is relatively simple to perform and requires minimal labour, whilst its precision for estimating micro quantities of asbestos ( < 200 ng) is much greater than by direct weighing.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Vital capacity and one-second forced expiratory volume in Australian male asbestos cement workers. L.N. Balaam, S.F. McCullagh. 1975;18(2):133-41. PubMed · Publisher
Giant cell formation after intraperitoneal application of crocidolite asbestos fibres in rats. S. Sethi, E.G. Beck, N. Manojlovic. 1974;17(1):53-6. PubMed · Publisher
Inter-laboratory comparisons of the counting of asbestos fibres sampled on membrane filters. S.T. Beckett, M.D. Attfield. 1974;17(2):85-96. PubMed · Publisher
Steelwork insulated with sprayed crocidolite asbestos: controlling a potential hazard. G.L. Lee, D.J. Smith. 1974;17(1):49-52. PubMed · Publisher
Asbestos in the work place and the community. M.L. Newhouse. 1973;16(2):97-107. PubMed · Publisher

Abstract

The fibrogenic properties of asbestos dust were detected early, later knowledge accumulated about the carcinogenic properties of the mineral and a hazard of bronchial carcinoma and mesothelial tumours was recognised. Mortality studies have measured the effect of exposure on working populations. Recent analysis of data from a cohort of asbestos factory workers shows that even with low to moderate exposure there is excess mortality from cancer of the lung and pleura and other cancers, after more than 25 years' observation. The mesothelioma rate increases both with severity and length of exposure. Occurrence of these and other tumours appears to be dose-related. The markers of a community effect of asbestos dust in the environment are the occurrence of mesothelial tumours in neighbourhoods of a source of asbestos dust, and the presence of asbestos bodies or calcified asbestos pleural plaques in the general population. Conditions giving rise to neighbourhood mesothelial tumours may not now occur, but the importance of adequate control in all countries where asbestos is mined or manufactured is stressed.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Some observations on the distribution of trace metals in chrysotile asbestos. A. Morgan, A.E. Lally, A. Holmes. 1973;16(3):231-40. PubMed · Publisher

Abstract

The distribution of iron, chromium, nickel, cobalt and scandium in a number of samples of chrysotile asbestos, including the standard reference samples prepared under the auspices of the International Union Against Cancer (UICC) was investigated. The composition of material separated magnetically from chrysotile was examined, using radioactive tracer methods. The solubility of these elements was measured by leaching samples of chrysotile in N hydrochloric acid at 25 °C and compared with the solubility of the structural magnesium. These investigations show that all the metals considered can replace magnesium in the brucite layer of chrysotile. In addition, however, with the possible exception of scandium, they are also present in accessory minerals associated with the fibre.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The evaluation of airborne asbestos fibres using a scanning electron microscope. S.T. Beckett. 1973;16(4):405-8. PubMed · Publisher

Abstract

Asbestos fibres sampled on Nuclepore filters can be directly examined by scanning electron microscope in much greater detail than is possible using the conventional optical microscope/membrane filter technique. Results obtained by the two methods for fibres > 5 µm in length were in good agreement. The new technique could facilitate the development of automatic counting methods for asbestos fibres.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Chromium and nickel. G. Kazantzis. 1972;15(1):25-31. PubMed · Publisher

Abstract

Chromium and nickel are two elements shown to have a limited but definite carcinogenic potential in man. Workers engaged on the production of chromates from the raw material, chrome iron ore, have experienced an increased mortality from lung cancer. Exposure to chromates or bichromates in industries where these compounds are used rather than manufactured, while producing epithelial ulceration, has not been shown to be associated with an increased mortality from cancer. However, no detailed epidemiological study of such workers has been performed. Nickel refinery workers have experienced an increased mortality from cancer of the nose and from cancer of the lung. The evidence suggests that this risk is not experienced by workers who have only been employed in refineries modified to reduce exposure to nickel compounds. Chromium compounds have a limited carcinogenic potential in experimental situations whilst many nickel compounds have been shown to be tumorigenic.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Current opinions on the asbestos cancer problem. J.C. Wagner. 1972;15(1):61-5. PubMed · Publisher

Summary

This article was a synopsis of a recent review of epidemiological studies and a general summary by the same author, drawing on opinions expressed at the 1969 Pneumoconiosis Conference in Johannesburg. The author described international studies sponsored by the International Union Against Cancer and the International Agency for Research on Cancer. A large survey of Quebec chrysotile miners showed a slight excess of lung cancer in the most heavily exposed group and no recorded mesotheliomas. Similar findings were reported for the Urals, Rhodesia, Italy and Finnish anthophyllite miners, and no mesotheliomas were observed in the Transvaal amosite areas. This contrasted with the North West Cape crocidolite fields. Lung cancer death rates among New York insulation workers were seven times those expected. Mesotheliomas were reported from shipbuilding ports where crocidolite had been used. In animal experiments, intrapleural chrysotile induced tumours as readily as crocidolite. The author discussed physical studies of fibre deposition. In rats exposed by inhalation, amphibole retention was six times that of chrysotile. North West Cape and Australian crocidolite fibres were thinner and shorter than Transvaal fibres. The author concluded that excessive exposure to all fibre types could cause lung cancer and that present evidence tended to implicate crocidolite in mesothelioma. He advised that crocidolite use should be restricted except where essential and that amosite required a high standard of dust control. He considered that chrysotile may carry only a small risk under practical dust control.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
The combined effects of smoking and occupational or urban factors in relation to lung cancer. R.E. Waller. 1972;15(1):67-73. PubMed · Publisher

Abstract

In this brief review, some of the published work on lung cancer mortality has been considered in relation to possible "interactions" between smoking and other factors. Although there is evidence to suggest that smoking enhances the lung cancer risk in certain occupational groups, studies on general populations show that the effect of smoking is large compared with that of "urban" factors and there is no indication of any interaction between smoking and air pollution.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
A comparison of mass and fibre concentrations of asbestos dust in shipyard insulation processes. P.G. Harries. 1971;14(3):235-40. PubMed · Publisher

Abstract

Measurements have been made of the mass and fibre concentrations of dust produced during shipyard processes involving asbestos insulating materials. Comparison of the results of measuring total dust, 'respirable' dust and fibre concentration show that gravimetric measurements are not suitable for environmental monitoring in Naval Dockyards. The membrane filter technique for estimating fibre concentration is recommended for that purpose.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Asbestos dust concentrations in ship repairing: a practical approach to improving asbestos hygiene in naval dockyards. P.G. Harries. 1971;14(3):241-54. PubMed · Publisher

Abstract

A survey of the asbestos fibre concentrations associated with work involving asbestos insulating materials has been undertaken in Devonport Dockyard. The results show that application and removal of asbestos materials both create high dust concentrations, and measures to reduce the health hazards associated with such processes are described. The results of sampling after the introduction of preventive measures are briefly presented and these results indicate that the precautions are effective in reducing the asbestos dust concentrations in shipyard insulation processes.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Asbestos dust levels inside firefighting helmets with chrysotile asbestos covers. K.P. Lumley. 1971;14(3):285-6. PubMed · Publisher
Buildings insulated with sprayed asbestos: a potential hazard. K.P. Lumley, P.G. Harries, F.J. O'Kelly. 1971;14(3):255-7. PubMed · Publisher

Abstract

In a survey of storehouses insulated with sprayed crocidolite and amosite asbestos the insulation was found to be damaged because it was unprotected. Dust sampling tests showed that the occupants of these storehouses could be exposed to harmful levels of asbestos dust if the insulation or fallen asbestos debris was disturbed. It is suggested that this hazard may be controlled by sealing the insulation and providing means of protecting the sealed insulation against damage.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The Konimiser--a dispenser for the continuous generation of dust clouds from milligram quantities of asbestos. R.F. Hounam. 1971;14(4):329-35. PubMed · Publisher
Asbestos and asbestosis. W.J. Smither. 1970;13(1):3-5. PubMed · Publisher
Asbestos hazard from protective clothing. H.A. Bamber, R. Butterworth. 1970;13(1):77-9. PubMed · Publisher
Asbestos release from battery boxes. M. Greenberg. 1970;13(1):79-80. PubMed · Publisher
Control of the use of asbestos-containing friction materials. M.L. Bentley. 1970;13(1):31-2. PubMed · Publisher
Exposure to asbestos during brake maintenance. D.E. Hickish, K.L. Knight. 1970;13(1):17-21. PubMed · Publisher
Hygiene standards for asbestos. S.A. Roach. 1970;13(1):7-15. PubMed · Publisher

Summary

This paper, first presented at a 1969 conference on asbestos exposure during brake and clutch maintenance, described how the British Occupational Hygiene Society's Sub-committee on Asbestos derived new hygiene standards for airborne chrysotile dust, and compared them with American standards. The standards were based on a medical and environmental study of 290 men employed at an English asbestos textile factory between 1933 and 1966. Exposure was expressed in fibre years/cm3, the average concentration of fibres longer than 5 µm (membrane filter counts) multiplied by years of exposure. Concentrations had ranged from 1 to 27 fibres/cm3 over 10 to 33 years. The author explained the dose-response principles involved and argued that there is no single threshold. A curve fitted to the prevalence of basal rales indicated that, for an accumulated exposure of 100 fibre years/cm3, the risk of early clinical signs of asbestosis would probably be less than 1 per cent. This corresponded to a 3-monthly average of 2 fibres/cm3 over a 50-year working life. The American limit of 5 million particles/ft3, set in 1938, was described as about 17 times higher, and the paper summarised the ACGIH's 1968 proposal for a time-weighted limit equivalent to 12 fibres/cm3. The Sub-committee had not decided whether the standards suited amosite or crocidolite, or protected against lung cancer or mesothelioma. The author concluded that deciding what level of dust control is acceptable was more uncertain than the exposure-risk relationship, and that more information on control costs was needed.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Possible alternatives to asbestos as a friction material. D. Hatch. 1970;13(1):25-9. PubMed · Publisher

Summary

This paper, presented at a March 1969 conference on exposure to asbestos during brake and clutch maintenance, discussed possible alternatives to asbestos in friction materials. The author, from the friction-material maker Ferodo, traced brake linings from oil-impregnated cotton to woven and then moulded asbestos. He argued that no substitute could replace asbestos in conventional drum brake linings without loss of performance and strength. He noted that disc brake pads, oil-immersed automatic transmission clutches and spider clutches allowed less asbestos or none. He stated that friction materials used chrysotile, that heat converts chrysotile to non-fibrous olivine minerals, and that about 1 per cent of asbestos remains in wear products, much of it ground to less than 5 µ. In tests on employees' cars and company trucks, brake drums were cleaned with a compressed-air jet in an unventilated garage, and instantaneous samples were taken from the dust cloud. Across seven samples, counts of fibres above 5 µ ranged from 2.1 to 8.2, against non-fibrous counts of 109 to over 2000, with a 10-minute average of 0.8. The author did not recommend compressed-air cleaning but concluded that wear products were probably no more dangerous than many other dusts. He listed glass fibre, steel wool, mineral wool, carbon fibres, and sintered metals and cermets as possible substitutes, each with drawbacks, and judged sintered metals and cermets probably the best eventual possibility.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.
Respirators for protection against asbestos. S. Luxon. 1970;13(1):41. PubMed · Publisher
Technical implementation of the new asbestos regulations. S. Luxon. 1970;13(1):23-4. PubMed · Publisher
The control of asbestos in the working environment. J.M. Ellison, W.P. Howard. 1970;13(2):153-8. PubMed · Publisher

Summary

This report summarised a joint all-day conference on "The control of asbestos in the working environment", held in London on 18 June 1969 by the British Occupational Hygiene Society and the Asbestosis Research Council. The conference was timed to follow the publication of the Asbestos Regulations 1969. Papers and discussions covered health effects, hygiene standards, legislation, monitoring, medical supervision and dust control. Dr J. C. Gilson described asbestosis, pleural fibrosis, bronchial cancer, mesothelioma and asbestos corns. He reported that 550 mesothelioma cases had been recorded in the United Kingdom, that about 60 were added to the register each year, and that 70-80 per cent were associated with asbestos. He suggested that perhaps 1-3 per cent of occupationally exposed people developed these tumours, about 20 years or more after first exposure. Dr S. A. Roach explained the Society's fibre-count-based standards for chrysotile. Mr B. H. Harvey outlined how the 1969 Regulations extended controls to every branch of industry. These included notifying the Factory Inspectorate before using crocidolite or stripping old lagging containing it. Dr S. Holmes described sampling and counting methods. He called dividing the chrysotile limit of 2 fibres/cm³ by 10 for crocidolite "completely arbitrary". Dr W. J. Smither described initial and periodic medical examinations. He reported that, at one asbestos factory, improved control had extended the average latent period before asbestosis became evident from 7 to 17 years. Other speakers addressed trade union concerns, medical record linkage, dust suppression and the design of dust control systems.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

1960s

A dust survey carried out in buildings incorporating asbestos-based materials in their construction. J.C. Byrom, A.A. Hodgson, S. Holmes. 1969;12(3):141-5. PubMed · Publisher
A simple dispenser for generating dust clouds from standard reference samples of asbestos. V. Timbrell, A.W. Hyett, J.W. Skidmore. 1968;11(4):273-81. PubMed · Publisher

Abstract

This dispenser has been developed for the economical generation of dust clouds from the five UICC reference samples of asbestos which are now available for distribution to research centres. The consumption rate of any sample to produce a mass concentration of 12 mg/m³ of respirable dust in an airflow of 20 m³/hr is only 1 g/hr. An extended trial has demonstrated the reliability of the dispenser.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Asbestos bodies and mesothelioma. J. Stumphius, P.B. Meyer. 1968;11(4):283-93. PubMed · Publisher

Abstract

The relation between exposure to asbestos and the occurrence of neoplasia is reviewed and it is concluded that the increasing use of asbestos will result in an increasing incidence of tumours. It is known that inhalation of asbestos fibres results in the formation of asbestos bodies in the lungs. Typical asbestos initiated tumours-pleural and peritoneal mesothelioma-were found at an unusually high frequency in shipyard-workers. Only slight asbestos exposure had taken place in these cases. On the other hand the persons involved had been exposed to high concentrations of iron oxide (flame cutters and welders). Objects similar to asbestos bodies were found in their lungs. Originally it was thought that these were pseudo asbestos bodies, containing an iron oxide core, and it was suspected that pseudo asbestos bodies might play a part in the genesis of the tumours. Investigations carried out at TNO institutes showed that the kernel of the bodies contained asbestos of the amphibole type thus proving that they were not pseudo but normal asbestos bodies. The simultaneous exposure to low concentrations of asbestos and high concentrations of iron oxide raises the suspicion that iron oxide might be an important cofactor in the genesis of mesothelioma found in the shipyard-workers. Experiments with different types of asbestos and iron oxide, on animals, are considered to be highly desirable in order to verify or disprove this hypothesis.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
Asbestos hazards in naval dockyards. P.G. Harries. 1968;11(2):135-45. PubMed · Publisher
The method used by the U.S. Public Health Service for enumeration of asbestos dust on membrane filters. G.H. Edwards, J.R. Lynch. 1968;11(1):1-6. PubMed · Publisher

Abstract

Samples of air-borne mineral dusts are collected by drawing air through cellulose ester membrane filters. Particles smaller than nominal pore size are retained. Varying sampling rate and filter holder controls the distribution of dust across the filter face. Samples are mounted on standard microscope slides using a high viscosity solution of membrane filter material in a mixture of diethyl oxalate and dimethyl phthalate to render the filter transparent. The mount is stable for 28-30 days, but after this period migration of the dust particles causes a loss of areal concentration. The grain and fiber dust particles, which lie on the surface of the filter, are counted with a phase contrast microscope, using 10X eye-pieces and a 4 mm "high-dry" objective. The field area is delineated with a Porton graticule. Count data are recorded in a form allowing data reduction and statistical analysis by electronic computer. The method, although not suitable to determine compliance with the threshold limit value for asbestos that was developed from a different enumeration method, is highly suited for developing basic data for a more precise recommendation of the limit for asbestos.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.
The newer pneumoconioses (with special regard to foundry risks). W.W. Jones. 1967;10(3):241-8. PubMed · Publisher

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