Re: "TLVs for asbestos"

Our plain-English summary of Re: "TLVs for asbestos", by G.W. Schepers (American Journal of Industrial Medicine, 1993).

The study

• Author: G.W. Schepers
• Journal: American Journal of Industrial Medicine
• Published: 1993;23(6):967-9
• Type of article: Comment, Letter
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This is a letter to the editor, not a research study. It reports no new data. The author replied to a 1992 letter by the late Professor Warren Cook, who had said that the 1946 asbestos Threshold Limit Value (TLV) of the American Conference of Governmental Industrial Hygienists (ACGIH) was 5 million fibers per cubic foot of air. The author argued that ACGIH had actually recommended 5 million particles per cubic foot (5 mppcuft). In the author's account, no official practical method for counting fibers at work sites had been published by 1946, and ACGIH had no fiber-based asbestos TLV before 1970. The author also disputed Cook's description of the 1938 U.S. Public Health Service asbestos textile study. The author found reference to four factories, not six, and noted that the study reported airborne asbestos fibers averaging 9% of breathing-zone dust, with a range of 1% to 25%. The author added that some textile workers had still developed disabling asbestosis within less than 20 years. The author also argued that a TLV had no value unless asbestos-containing products were clearly labelled with safety instructions.

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: Letter to the editor (commentary replying to another letter); no original data
• Who was studied: No study population. The letter responds to Professor Warren Cook's 1992 letter about the 1946 ACGIH asbestos TLV and discusses the 1938 USPHS study of the asbestos textile industry.
• Exposure: How airborne asbestos dust was measured for the 1946 ACGIH TLV: counting particles versus counting fibers (including chrysotile fibers)
• Main results:
  • The author stated that ACGIH had no fiber-based asbestos TLV before 1970.
  • The author stated that no official practical methodology for fiber counting at work sites had been published by 1946.
  • The author stated that many optical microscopes of 1946 to 1970 could resolve only structures thicker than about 1 micron, so most chrysotile fiber bundles would have been invisible.
  • The author stated that, by 1946, there had been no experimental or epidemiological studies focused on 5 micron fibers. The author also said that earlier work by others had shown fibers as short as 2 microns caused fibrosis and cancer.
  • On the 1938 USPHS textile study, the author found reference to four factories rather than the six Cook described, and said only two of them received raw asbestos.
  • The author noted that the USPHS textile study reported aerosolized asbestos fibers in breathing zones averaging 9%, with a range of 1% to 25%.
  • The author noted that some employees of those textile factories had developed disabling asbestosis within less than 20 years.
  • The author argued that a TLV would have had no value unless all asbestos-containing products were clearly labelled with safety instructions for workers.
• The authors' conclusion: The author concluded that Professor Cook's interpretation of the 1946 ACGIH TLV as a fiber-based limit was entirely wrong.

Related studies

• Re: "TLVs for asbestos" — G.V. Coles (1993)
• ACGIH TLVs: a critical analysis of the documentation — P.A. Breysse (1991)
• Re: "TLVs for asbestos" — T.F. Mancuso (1993)
• Time to reconsider TLVs — L. Djerassi (1988)
• The hygiene standard for chrysotile asbestos — J. Peto (1978)
• Industrial hygiene and occupational health studies in Australian (New South Wales) shipyards — A. Bell (1976)

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