Asbestosis

Our plain-English summary of Asbestosis, by R.R. Sayers, W.C. Dreessen (American Journal of Public Health and the Nation's Health, 1939).

The study

• Authors: R.R. Sayers, W.C. Dreessen
• Journal: American Journal of Public Health and the Nation's Health
• Published: 1939;29(3):205-14
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

In plain English

This 1939 paper briefly reviewed the principal findings of a U.S. Public Health Service engineering and medical study of the asbestos textile industry in North Carolina. The main raw material was Canadian chrysotile. The investigators made 242 dust counts and examined 541 men and women from three factories. Pulmonary asbestosis was the principal physical defect found. The most serious forms were seen in carders, spinners, weavers, twisters, willowers and pickers. Asbestosis bodies were found in the sputum of 46.9 per cent of persons diagnosed with asbestosis and 24.3 per cent of essentially normal exposed persons. The authors read them only as evidence of exposure. The percentage with asbestosis rose with length of employment. No ground-glass X-ray markings were seen in workers exposed to less than 5 million particles per cubic foot. None of 39 people exposed below 2.5 had asbestosis, though only 6 had worked over 5 years. The authors tentatively proposed 5 million particles per cubic foot as a threshold. High labor turnover and the plants' short operating history prevented an exact estimate of incidence.

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: Summary of a cross-sectional engineering (dust measurement) and medical examination study of asbestos textile workers, the full report of which was published separately as Public Health Bulletin No. 241
• Who was studied: 541 men and women, practically all employees at the time of study, in three asbestos textile factories in North Carolina that had operated 6 to 16 years. Comparison X-ray groups were 229 men never employed in a dusty trade and 80 men in wet kaolin mining and refining.
• Exposure: Asbestos textile dust, mainly Canadian chrysotile, made up of particles and fibers. Measured exposures ranged from 0.10 to 76 million particles per cubic foot (m.p.p.c.f.) across jobs such as willowing, picking, carding, spinning, twisting and weaving.
• Main results:
  • Among the 541 employees examined, pulmonary asbestosis was the principal physical defect found.
  • The most serious forms of asbestosis were observed in carders, spinners, weavers, twisters, willowers and pickers.
  • Asbestosis bodies were found in the sputum of 46.9 per cent of persons diagnosed with asbestosis and of 24.3 per cent of essentially normal asbestos-exposed persons.
  • Asbestosis bodies were not seen in anyone with less than 3 months' exposure. Because they can appear before significant fibrosis, the authors interpreted them as showing evidence of exposure only.
  • None of the 309 comparison men (229 never in a dusty trade, 80 kaolin workers) had ground-glass lung markings on X-ray.
  • Among asbestos workers, no cases of ground-glass X-ray markings occurred in the group exposed to less than 5 m.p.p.c.f.
  • The percentage of workers with asbestosis increased greatly with length of employment, and also with dust concentration.
  • None of 39 persons exposed below 2.5 m.p.p.c.f. had asbestosis, though only 6 of them had been employed more than 5 years. Three doubtful cases fell in the 2.5 to 4.9 m.p.p.c.f. range.
  • A supplemental engineering study at a factory with newly installed dust control (exhaust ventilation) showed that most workers' exposure could be reduced below 5 m.p.p.c.f.
• The authors' conclusion: The authors tentatively regarded 5 m.p.p.c.f. as a threshold value for asbestos dust exposure. They concluded that it appears new cases of asbestosis will not appear if dust concentrations are kept below that level. They also stressed that occupational history, clinical examination and X-ray must all be considered for diagnosis.
• Limitations the authors state:
  • Large labor turnover and the short time the plants had operated meant no exact estimate of the incidence of asbestosis could be made.
  • Few cases had more than 15 years' exposure, so the authors described the percentages with asbestosis as minimal estimates of prevalence.
  • Unexpectedly lower rates of ground-glass markings at 10 to 19.9 m.p.p.c.f. were probably sampling errors due to small numbers of exposed persons.

Related studies

• Mechanisms in the pathogenesis of asbestosis and silicosis — B.T. Mossman, A. Churg (1998)
• Inhibition of lung injury, inflammation, and interstitial pulmonary fibrosis by polyethylene glycol-conjugated catalase in a rapid inhalation model of asbestosis — B.T. Mossman, J.P. Marsh, et al. (1990)
• Pulmonary endpoints (lung carcinomas and asbestosis) following inhalation exposure to asbestos — B.T. Mossman, M. Lippmann, et al. (2011)
• Asbestos-related pleural disease and asbestosis: a comparison of CT and chest radiography — A.C. Friedman, S.B. Fiel, et al. (1988)
• Pulmonary Asbestosis — W.E. Cooke (1927)
• Asbestosis and silicosis — G.R. Wagner (1997)

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