Effects of the Inhalation of Asbestos Dust Upon the Lungs of Asbestos Workers

Our plain-English summary of Effects of the Inhalation of Asbestos Dust Upon the Lungs of Asbestos Workers.

The study

• Published: Metropolitan Life Insurance Company, Industrial Health Service and Industrial Hygiene Division
• Type of article: Report
• 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 report described a survey of asbestos mines and mills in Quebec, Canada. It was carried out jointly by the Metropolitan Life Insurance Company's Industrial Health Service and McGill University's medical school. Investigators measured dust where men worked and examined workers, including chest X-ray films. The dust was described as about 5 per cent asbestos fibre, the rest rock dust. In every sample, at least 93 per cent of particles were 10 microns or smaller. Of 156 X-ray examinations, 3 were diagnosed as second-stage asbestosis, 19 as first-stage, 35 as doubtful and 99 as negative. No third-stage (marked disability) cases were found. Only 9 of the 22 workers with asbestosis were free of symptoms. Of those 22, 15 had over 15 years of exposure and none had under 5 years. The films showed an unusual incidence of heart enlargement. The authors concluded that prolonged exposure to asbestos dust causes a lung fibrosis distinct from silicosis. They also concluded that the asbestosis observed did not cause marked disability and that mill dust could be substantially reduced. They noted they could not link individual cases to measured dust amounts.

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: Cross-sectional workplace survey combining air dust measurements with physical and chest X-ray examinations of workers
• Who was studied: Men actively working in asbestos mines and mills in the Province of Quebec, Canada; 156 X-ray examinations; the plants were designated by letters
• Exposure: Airborne asbestos mine and mill dust, described as about 5 per cent asbestos fibre and the rest rock dust; fibre type not named. Dust was sampled with an impinger and counted in million particles per cubic foot of air
• Main results:
  • Of 156 X-ray examinations (printed by the scan as 'l56'; the four groups add up to 156), 3 were diagnosed as second-stage (second degree) asbestosis, 19 as first-stage, 35 as doubtful and 99 as negative
  • No cases were found that would have been classed as third stage (extensive lung involvement with marked or total disability)
  • 9 of 22 workers diagnosed with asbestosis were free of symptoms, compared with 13 of 35 classed as doubtful and 17 of 99 classed as negative
  • Among the 22 workers with asbestosis, 15 had over 15 years of exposure, 5 had 10 to 15 years, 2 had 5 to 10 years and none had under 5 years
  • In every air sample, particles 10 microns and under made up at least 93 per cent of all particles
  • The X-ray films showed an unusual incidence of heart enlargement among these workers, which the authors considered probably compensatory
• The authors' conclusion: The authors concluded that prolonged exposure to asbestos dust causes a pulmonary fibrosis distinct from silicosis that shows on X-ray films, and that asbestosis is often associated with heart enlargement. They concluded that it did not appear to increase susceptibility to tuberculosis and, as observed in this series, did not cause marked disability. They added that it was not yet practicable to set dust standards for asbestos and that dust in the mills could be substantially reduced.
• Limitations the authors state:
  • Dust was measured only at the time of the survey, so the authors could not know workers' average past exposure or correlate individual cases with dust amounts
  • Workers were classified by their present occupation or the one where most of their time was spent, and many had changed jobs
  • It was unknown whether workers classed as doubtful would progress to definite asbestosis

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Fibrosis, Silicosis.

Browse return to medical research.