An experiment to develop conversion factors to standardise measurements of airborne asbestos

Our plain-English summary of An experiment to develop conversion factors to standardise measurements of airborne asbestos, by M. Dodic-Fikfak (Arhiv Za Higijenu Rada I Toksikologiju, 2007).

The study

• Author: M. Dodic-Fikfak
• Journal: Arhiv Za Higijenu Rada I Toksikologiju
• Published: 2007;58(2):179-85
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Various researchers and agencies recommend different conversion factors for different asbestos exposures. The aim of this study was to develop conversion factors from particles per cm3 (p cm(-3)) to fibres per cm3 (f cm(-3)) and from mg m(-3) to f cm(-3). More than 1000 exposure measurements were available in the Slovenian asbestos-cement factory Salonit Anhovo. Three types of measurement of asbestos concentrations in the air were used: a konimeter measuring p cm-3, a gravimetric method measuring mg m-3 and a membrane filter method measuring f cm-3. Operation-specific conversion factors among these methods were developed. One conversion factor was obtained for asbestos-pipe-dry jobs (4.7) and one for asbestos-sheet-dry jobs (1.6). Only one conversion factor (0.8) was used for asbestos-cement-pipe-wet and asbestos-cement-pipe-dry jobs. For asbestos cement sheets, two conversion factors were obtained (0.3 and 1.2). The development of five different conversion factors made it possible to calculate cumulative exposure to asbestos from historical data and to decrease exposure misclassification.

In plain English

This study used air-monitoring records from Salonit Anhovo, Slovenia's only cement-asbestos plant, to develop factors for converting measurements into fibres per cubic centimetre. About 1030 measurements from 1961 to 1995 used three methods: konimeter (particles per cm3), gravimetric (milligrams of respirable dust per cubic metre) and membrane filter (fibres per cm3). To convert mass to fibres, the author used 78 pairs of side-by-side measurements (60 pairs from the pipe department, 18 from the sheet department), grouped by product, department and wet or dry process. Five factors resulted: 4.7 for asbestos-pipe dry jobs, 1.6 for asbestos-sheet dry jobs, a single 0.8 for asbestos-cement pipe jobs (whose wet and dry ratios were 0.9 and 0.7), and 0.3 for wet and 1.2 for dry asbestos-cement sheet jobs. These were generally lower than the European Community factor. The article reports no numeric konimeter factors. The factors were needed for a nested case-control study in a cohort of almost 7000 workers. The author concluded that they made calculating cumulative exposure possible and decreased exposure misclassification, while acknowledging doubt about whether such conversion is possible.

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: Exposure-assessment methods study developing conversion factors from historical workplace air measurements, for use in a nested case-control study in a cohort of almost 7000 workers at the factory
• Who was studied: About 1030 air measurements taken between 1961 and 1995 at Salonit Anhovo, the only cement-asbestos plant in Slovenia. The gravimetric to fibre conversion used 78 paired measurements (60 measurement pairs from the pipe department and 18 from the sheet department).
• Exposure: Airborne asbestos and asbestos-cement dust in the asbestos-cement pipe and sheet manufacture departments, in wet and dry processes. It was measured by konimeter (particles per cm3), by a gravimetric method (mg per m3 of respirable dust) and by a membrane filter method (fibres per cm3). The article does not name fibre types.
• Main results:
  • All workplaces with exposure only to asbestos were dry. They gave one conversion factor for asbestos-pipe-dry jobs (4.7) and one for asbestos-sheet-dry jobs (1.6).
  • Asbestos-cement pipe jobs: wet jobs were heavily influenced by dry emissions from nearby pipe finishing, and the ratios were close (0.9 and 0.7). A single factor of 0.8 was therefore used for wet and dry asbestos-cement pipe jobs.
  • In Figure 1, the asbestos-cement pipe ratio was 0.9 for wet jobs (10 observed ratios) and 0.7 for dry jobs (43 observed ratios).
  • Asbestos-cement sheets: two conversion factors were obtained. Figure 1 gives 0.3 for wet jobs (6 observed ratios) and 1.2 for dry jobs (8 observed ratios).
  • In total, five conversion factors from mg per m3 to fibres per cm3 were obtained for the two departments.
  • The developed factors were generally lower than the European Community factor of 2 fibres per cm3 per 0.1 mg per m3.
• The authors' conclusion: The author concluded that developing five conversion factors made it possible to calculate cumulative asbestos exposure from historical data and to decrease exposure misclassification. The author also stated a belief that there is hardly a more appropriate method to use with the available data.
• Limitations the authors state:
  • Only a limited number of paired data points was available, so a non-parametric method was used.
  • The author acknowledged limitations of the non-parametric method and doubt about whether conversion from one measurement unit to another is possible at all.
  • How much product and process characteristics affect airborne fibre concentration is not known.
  • No side-by-side konimeter and membrane filter measurements existed. Instead, 16 membrane filter measurements from 1974/75 were compared with the nearest konimeter measurements (n=31), which dated from 1969.
  • The author noted that almost all calculated conversion factors are an approximation.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Asbestos-Cement, Membrane Filter Method, Cumulative Exposure.

Related studies

• 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)
• A comparison of parallel dust and fibre measurements of airborne chrysotile asbestos in a large mine and processing factories in the Russian Federation — E. Feletto, S.J. Schonfeld, et al. (2017)
• 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, et al. (1982)
• Comparative assessing for radiological, chemical, and physical exposures at the French uranium conversion plant: Is uranium the only stressor? — I. Guseva Canu, F. Paquet, et al. (2009)
• Personal and static sample measurements of asbestos fibres during two abatement projects — A. Dufresne, C. Dion, et al. (2009)
• A comparison of historic asbestos measurements using a thermal precipitator with the membrane filter-phase contrast microscopy method — G. Burdett (1998)

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