Evaluation of Asbestos Exposures in the Working Environment: Recommendation of Subcommittee on Asbestosis of the Permanent Commission and International Association on Occupational Health

Our plain-English summary of Evaluation of Asbestos Exposures in the Working Environment: Recommendation of Subcommittee on Asbestosis of the Permanent Commission and International Association on Occupational Health (1972).

The study

• Published: Journal of Occupational Medicine, vol. 14, no. 7 (July 1972), p. 560 ff. (Special Article)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1972 document was not a study of workers or disease. It was a set of recommendations from the Sub-Committee on Asbestosis of the Permanent Commission and International Association on Occupational Health on how to collect, count and describe respirable asbestos fibers in workplace air. The subcommittee noted that countries measured fibers in different ways, which made their data hard to compare. It recommended membrane filter sampling, with samples taken at workers' breathing zone for health studies and for checking compliance with standards. Fibers longer than 5 micrometers were to be counted with phase contrast microscopy, and fibers wider than 5 micrometers were to be excluded. It recommended identifying the fiber type (such as chrysotile, amosite or crocidolite). It also recommended measuring free silica when evaluating workers' exposure at operations where silica might approach its exposure standard, and, for research, measuring metals and organic contaminants. It noted that the biologic importance of submicron fibers was largely unknown. It urged countries using other methods, such as the konimeter, to also use the recommended methods so their data could be compared and pooled.

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: Expert committee recommendation on workplace air sampling and fiber-counting methods (not a study of people or animals)
• Who was studied: No study population. The recommendations cover airborne asbestos fibers in working environments.
• Exposure: Respirable airborne asbestos fibers. Fiber types such as chrysotile, amosite and crocidolite were to be identified. Associated metals, free silica and polycyclic aromatic hydrocarbons were also covered.
• Main results:
  • Recommendation: the membrane filter technique should be used to collect airborne asbestos fibers.
  • Recommendation: samples for health studies and compliance checks should be collected at the workers' breathing zone. Fixed-site samples may be used to check that dust control equipment is working.
  • Recommendation: fibers should be counted by phase contrast microscopy and expressed per cubic centimeter. Fibers longer than 5 micrometers were to be counted, and fibers wider than 5 micrometers were to be excluded. In the scanned text, the length-to-diameter ratio that defines a fiber reads '4 1o 1'. That number could not be confirmed from the text.
  • Recommendation for research: some samples should be examined by both optical and electron microscopy, because the biologic importance of submicron fibers was largely unknown.
  • Recommendation: the ratio of respirable asbestos fibers to total respirable particulates should be determined.
  • Recommendation for research: airborne samples should be analyzed for biologically active metals.
  • Recommendation: when evaluating the asbestos worker's exposure, free silica should be measured at strategic operations where it may be present in amounts approaching the exposure standard for silica.
  • Recommendation for research: cyclohexane-extractable organic materials should be measured in airborne samples of respirable asbestos dust.
  • Recommendation: countries using other methods, such as the konimeter and bright field projection microscopy, should also use the recommended procedures at the same time so the data can be compared.
• The authors' conclusion: The subcommittee stated that uniform procedures would let data from different countries be related to one another and combined in a shared data bank, increasing the reliability of the data.
• Limitations the authors state:
  • Counting submicron fibers would require electron microscopy, which the subcommittee considered too time-consuming and costly for routine counting.
  • Counting only fibers 5 micrometers or longer may not always be a valid index of exposure.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, phase contrast microscopy (PCM), Chrysotile, Amosite, Crocidolite.

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