Estimating past inhalation exposure to asbestos: A tool for risk attribution and disease screening

Our plain-English summary of Estimating past inhalation exposure to asbestos: A tool for risk attribution and disease screening, by J.W. Cherrie, D. McElvenny, K.G. Blyth (International Journal of Hygiene and Environmental Health, 2018).

The study

• Authors: J.W. Cherrie, D. McElvenny, K.G. Blyth
• Journal: International Journal of Hygiene and Environmental Health
• Published: 2018;221(1):27-32
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: Late presentation is common in mesothelioma. Reliable assessment of past exposure to asbestos is a necessary first step for risk attribution and for the development of a future screening programme. Such a programme could maximise access to trials of novel therapies and would pave the way for development of novel chemoprophylaxis strategies. This paper describes a method for individual exposure reconstruction along with data from a validation study.

Methods: The exposure assessment method uses only descriptive information about the circumstances of the work that could be obtained from questioning the worker. The assessment is based on the tasks carried out and includes parameters for substance emission potential, activity emission potential, the effectiveness of any local control measures, passive emission, the fractional time the asbestos source is active and the efficiency of any respiratory protection worn.

Results: There was a good association between the estimated and measured exposure levels. Pearson's correlation coefficient between the log-transformed measurements and estimates from the model was 0.86, and 95% of the estimated individual values were within about a factor of ten of the associated measured value. The method described would be suitable for pre-selecting individuals at high risk of malignant pleural mesothelioma for screening using appropriate tools and/or enrolment in clinical trials of chemo-prophylaxis.

Discussion: This method is of potential clinical value in developing novel treatment approaches for mesothelioma. Pilot studies to test this approach are urgently needed.

Copyright © 2017 Elsevier GmbH. All rights reserved.

In plain English

This paper described a method for estimating, after the fact, how much asbestos a worker breathed in, using only a description of the work, and tested it against air measurements. An assessor gives values to factors such as how dusty the asbestos material is, how it was handled, any local controls, background release and how much of the time the source was active. The authors applied the method to 32 work scenarios from published papers or in-house reports, each with between one and 23 measurements. Average measured levels ranged from 0.001 fibres/ml (reassembling an engine with new chrysotile gaskets) to 226 fibres/ml (grinding and grit blasting steel girders with crocidolite spray insulation). The authors reported a good association: the correlation between log-transformed estimates and measurements was 0.86, and 95% of estimates were within about a factor of ten of the measured value. The model tended to overestimate at lower exposures and underestimate at higher ones. Some estimates differed from measurements by more than ten-fold. The authors concluded the method could reconstruct individual exposure to within about an order of magnitude. They said pilot studies of its use in selecting people for screening are urgently needed.

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.

What the study did and found

• Design: Methods paper with a validation study comparing model-estimated asbestos exposure levels against measured levels for work scenarios
• Who was studied: 32 work scenarios selected from the published literature or in-house reports, each with between one and 23 measurements of inhalation exposure (median 5). For four scenarios only the mean and range were available.
• Exposure: Inhalation exposure to asbestos fibres during work tasks, measured during the tasks rather than as 8-hour averages. Average measured levels ranged from 0.001 fibres/ml (engine reassembly with installation of new chrysotile asbestos-containing gaskets) to 226 fibres/ml (grinding and grit blasting on steel girders with crocidolite spray insulation). No allowance was made for respirators, because the measurements were taken outside any respiratory protection.
• Main results:
  • Across the 32 scenarios, Pearson's correlation coefficient between the log-transformed measurements and the model estimates was 0.86. 95% of individual estimates were within about a factor of ten of the measured value.
  • The regression line relating estimates to measurements had r2 = 0.74. It was significantly different from the line of equality (p less than 0.001).
  • The model showed an apparent tendency to overestimate at lower exposure levels and underestimate at higher levels.
  • The 95% prediction interval around the regression line was just over an order of magnitude higher or lower.
  • In the asbestos-containing gasket removal scenario in a chemical plant (Scenario A31), the average measured value was 0.1 fibres/ml (range 0.051 to 0.24 fibres/ml), while the estimate was 0.002 fibres/ml (uncertainty range 0.001 to 0.005 fibres/ml). The source paper noted that only four of the 11 samples contained asbestos, and most fibres probably came from glass fibre lagging.
• The authors' conclusion: The authors concluded that the method has the potential to reconstruct individual asbestos exposure across a wide range of circumstances to within about an order of magnitude. In their view it could be suitable for pre-selecting people at high risk of malignant pleural mesothelioma for screening or chemoprophylaxis trials. They stated that feasibility and pilot studies are urgently needed.
• Limitations the authors state:
  • In a number of scenarios the estimate differed from the measured level by more than ten-fold.
  • The assessments showed an overall positive bias (overestimation). The authors said this either depends on the descriptive information used or is inherent to the method.
  • The descriptions used in this exercise could be quite brief. The authors said more detail would likely give more precise estimates.
  • Assessors may need to use their own judgement when details, such as how long the dust-generating activity lasted, are unavailable or unclear.

Topics

Medical terms in this study, explained in our Lexicon: Attribution, Mesothelioma, Exposure Reconstruction, Respirator, Pleural Mesothelioma, Clinical Trial.

Related studies

• Estimating exposures in the asphalt industry for an international epidemiological cohort study of cancer risk — I. Burstyn, P. Boffetta, et al. (2003)
• Lung cancer risk in past asbestos workers a few decades after exposure cessation and prospects for screening — G. Mastrangelo, G. Marangi, et al. (2016)
• Risk of gastrointestinal cancers from inhalation and ingestion of asbestos — J. Gamble (2008)
• Inhalation unit risk (IUR) of asbestos based on available science — A. Korchevskiy, J.O. Rasmuson, et al. (2020)
• Estimating the contribution of individual risk factors to disease in a person with more than one risk factor — P. McElduff, J. Attia, et al. (2002)
• Biological responses to asbestos inhalation and pathogenesis of asbestos-related benign and malignant disease — E. Solbes, R.W. Harper (2018)

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