History of knowledge and evolution of occupational health and regulatory aspects of asbestos exposure science: 1900-1975

Our plain-English summary of History of knowledge and evolution of occupational health and regulatory aspects of asbestos exposure science: 1900-1975, by C.A. Barlow, J. Sahmel, D.J. Paustenbach, et al (Critical Reviews in Toxicology, 2017).

The study

• Authors: C.A. Barlow, J. Sahmel, D.J. Paustenbach, J.L. Henshaw
• Journal: Critical Reviews in Toxicology
• Published: 2017;47(4):286-316
• Type of article: Review
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The understanding by industrial hygienists of the hazards of asbestos and appropriate ways to characterize and control exposure has evolved over the years. Here, a detailed analysis of the evolution of industrial hygiene practices regarding asbestos and its health risks, from the early 1900s until the advent of the national occupational health and safety regulatory structure currently in place in the US (early-to-mid 1970s) is presented. While industrial hygienists recognized in the early 1900s that chronic and high-level exposures to airborne concentrations of asbestos could pose a serious health hazard, it was not until the mid-1950s that the carcinogenic nature of asbestos began to be characterized and widespread concern followed. With the introduction of the membrane filter sampling method in the late 1960s and early 1970s, asbestos sampling and exposure assessment capabilities advanced to a degree which allowed industrial hygienists to more precisely characterize the exposure-response relationship. The ability of industrial hygienists, analytical chemists, toxicologists, and physicians to more accurately define this relationship was instrumental to the scientific community's ability to establish Occupational Exposure Levels (OELs) for asbestos. These early developments set the stage for decades of additional study on asbestos exposure potential and risk of disease. This was followed by the application of engineering controls and improved respiratory protection which, over the years, saved thousands of lives. This paper represents a state-of-the-art review of the knowledge of asbestos within the industrial hygiene community from about 1900 to 1975.

In plain English

This was a historical review, not a study of workers. The authors evaluated more than 1000 references on the period 1900 to 1975 to trace how industrial hygienists measured and controlled asbestos exposure. The review recounted that the ACGIH adopted a 5 million particles per cubic foot (mppcf) limit in 1946 for all asbestos types, based on a 1938 study. It described a 1960 South African report of over 30 pleural mesothelioma cases linked by its researchers to exposure at or near a crocidolite mine. The ACGIH's 1968 proposal was an eight-hour average of 2 mppcf or 12 fibers per cubic centimeter (f/cc) for fibers longer than 5 micrometers, plus a 5 mppcf ceiling. OSHA's 1972 standard set 5 f/cc as an eight-hour average and a 10 f/cc 15-minute peak, counting only fibers longer than 5 micrometers. In 1971 OSHA specified membrane filter sampling with phase contrast counting, which the authors noted cannot tell chrysotile from amphibole fibers. The authors concluded that slow development of accurate sampling and analysis methods caused confusion about dose-response relationship for different mineral types.

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: Historical literature review of industrial hygiene knowledge about asbestos from about 1900 to 1975
• Who was studied: No study population; more than 1000 published and archival references, mainly books and periodicals from 1900 to 1975
• Exposure: Occupational asbestos use as discussed in historical documents, including measurement techniques, exposure characterization and knowledge of hazards
• Main results:
  • The review reports that the ACGIH adopted a 5 mppcf limit for all asbestos mineral types, based on the 1938 Dreessen study
  • The review describes a 1960 South African report of more than 30 pleural mesothelioma cases, which its researchers attributed to exposures at or near a crocidolite mine
  • The review reports that in 1968 the ACGIH proposed a ceiling of 5 mppcf and an eight-hour time-weighted average of 2 mppcf or 12 f/cc for fibers longer than 5 micrometers
  • The review reports that OSHA's 1972 permanent standard set 5 f/cc as an eight-hour average and a 10 f/cc 15-minute peak for all asbestos forms
  • The review reports that the 1972 standard regulated only fibers longer than 5 micrometers
  • The review reports that OSHA specified membrane filter sampling with phase contrast counting in 1971
  • The authors state that the phase contrast microscopy (PCM) method cannot distinguish chrysotile from amphibole fibers
• The authors' conclusion: The authors concluded that the slow development of accurate sampling and analytical methods, ones able to identify biologically active fibers and the specific mineral type, caused confusion and ambiguity in industrial hygienists' understanding of the dose-response relationship

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Industrial Hygiene, Carcinogenic, Occupational Exposure, Engineering Controls, Respirator.

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