Asbestosis

Our plain-English summary of Asbestosis, by R.R. Sayers, W.C. Dreessen (1939).

The study

• Authors: R.R. Sayers, W.C. Dreessen
• Published: American Journal Of Public Health 29(3):205-214, March (1939)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 002904. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1939 paper briefly reviewed the main findings of a U.S. Public Health Service engineering and medical study of the asbestos textile industry in North Carolina. The main asbestos raw material used for textiles was Canadian chrysotile. Dust was measured in million particles per cubic foot (mppcf). Medical examinations covered 541 men and women, practically all employees of three factories. Pulmonary asbestosis was the principal physical defect found. Asbestosis bodies were found in the sputum of 46.9 per cent of persons diagnosed with asbestosis, and in no one with less than 3 months' exposure. The authors treated these bodies as evidence of exposure only. Ground-glass X-ray markings increased with length of employment, and no such markings were seen in workers exposed to less than 5 mppcf. None of 39 persons exposed below 2.5 mppcf had asbestosis, although only 6 had worked more than 5 years. Large labor turnover and the short time the plants had been operating meant no exact estimate of the incidence of asbestosis was possible. The authors tentatively proposed 5 mppcf as a threshold for asbestos dust exposure.

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: Brief review by the authors of their own cross-sectional engineering (dust measurement) and medical (clinical, X-ray, sputum) survey
• Who was studied: 541 men and women, practically all the employees at the time, at three North Carolina asbestos textile factories that had operated 6 to 16 years
• Exposure: Asbestos textile dust (particles and fibers), measured in million particles per cubic foot by process and occupation; the main asbestos raw material used for textiles was Canadian chrysotile
• Main results:
  • Pulmonary asbestosis was the principal physical defect found among the 541 employees
  • Willowers, pickers, carders, mule and ring spinners, twisters and cloth weavers were particularly liable to develop severe forms of asbestosis
  • Asbestosis bodies were found in the sputum of 46.9 per cent of persons diagnosed with asbestosis; the authors interpreted their presence as merely showing evidence of exposure
  • Asbestosis bodies were not observed in anyone surveyed with less than 3 months' exposure
  • Within each dust exposure group, the percentage of workers with ground-glass X-ray markings increased consistently with length of employment
  • No cases with ground-glass markings occurred in the group exposed to less than 5 mppcf
  • The percentage of persons with asbestosis increased greatly with length of employment and also with dust concentration
  • None of 39 persons exposed below 2.5 mppcf had asbestosis, although only 6 had been employed more than 5 years; three doubtful cases fell in the 2.5 to 4.9 mppcf range
  • A supplemental engineering study in a factory with newly installed dust control (exhaust ventilation) showed that most asbestos textile workers' dust exposure could be reduced to less than 5 mppcf
• The authors' conclusion: The authors tentatively proposed 5 mppcf as a threshold value for asbestos dust exposure. They concluded that it appeared new cases of asbestosis would not appear if concentrations were kept below this level, and that control methods were already available for most processes.
• Limitations the authors state:
  • Because of large labor turnover and the short time the plants had operated, no exact estimate of the incidence of asbestosis could be made
  • Few workers had long exposure, so the asbestosis percentages are necessarily minimal estimates
  • About 150 workers had been replaced shortly before the study, giving an abnormally large percentage with short employment and an abnormally small percentage with 10 years or more
  • Irregular differences in incidence between some dust levels probably reflected sampling errors due to small numbers of exposed persons

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Textile Industry, Chrysotile, Million Particles per Cubic Foot (mppcf), Asbestosis, Sputum.

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