Effects Of The Inhalation Of Asbestos Dust On The Lungs Of Asbestos Workers: A Preliminary Study

Our plain-English summary of Effects Of The Inhalation Of Asbestos Dust On The Lungs Of Asbestos Workers: A Preliminary Study, by A.J. Lanza, W.J. Mcconnell, J.W. Fehnel (1935).

The study

• Authors: A.J. Lanza, W.J. Mcconnell, J.W. Fehnel
• Published: Public Health Reports 50(1):1-12, January 4 (1935)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 003012.

In plain English

This 1935 preliminary report presented data from five US asbestos fabricating plants (A to E), part of a Metropolitan Life Insurance Co. investigation (October 1929 to January 1931) that also studied dust in Canadian asbestos mines and mills. The authors measured airborne dust, X-rayed 126 workers (108 men, 18 women) with more than 3 years of employment, and reviewed insurance claims. Of these, 4 were diagnosed with second-degree asbestosis, 63 first-degree, 39 doubtful and 20 negative. The percentage positive rose with years of exposure. Reviewers noted a very unusual incidence of heart enlargement on the films. Local physicians found no unusual amount of tuberculosis among these workers. An experimental exhaust installation reduced dust by 50 percent. The authors concluded that prolonged asbestos dust exposure caused a lung fibrosis different from silicosis and visible on X-ray, which from this study appeared clinically milder than silicosis, and that a predisposition to tuberculosis was not indicated. They noted that individual cases could not be linked to dust amounts and that small numbers left the role of age undetermined.

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: Preliminary industrial health survey: dust sampling, X-ray and physical examinations of workers, and review of group insurance death and disability claims. The wider investigation also studied dust in Canadian mines and mills, but only fabricating-plant data are reported.
• Who was studied: 126 persons (108 men, 18 women) working in asbestos fabricating plants (plants A, B, C, D and E) along the Atlantic Seaboard of the United States, chosen more or less at random from those with more than 3 years of employment. All but five were also given a physical examination. The study ran from October 1929 to January 1931. The insurance claims analysis covered 2,099 lives.
• Exposure: Asbestos dust in asbestos textile departments (preparation, carding, spinning, weaving), insulating departments, and molded brake-lining and clutch departments. In the carding, spinning and weaving rooms, asbestos made up about 25 percent of the material used, the rest mainly cotton. In the insulating departments of plant A it made up 5 percent, and in the brake-lining and clutch division of plant D about 25 percent. The article describes chrysotile as the most commonly encountered commercial asbestos but does not state the fiber type used in each plant.
• Main results:
  • Of the 126 workers X-rayed, 4 were diagnosed with second-degree asbestosis, 63 with first-degree asbestosis, 39 as doubtful and 20 as negative.
  • The percentage of workers diagnosed as positive increased with years of exposure.
  • Of the 64 workers who were physically examined and diagnosed with asbestosis, only 8 were entirely free from symptoms. In the doubtful group 10 of 37 were free from symptoms, and in the negative group 7 of 20. Dyspnoea and cough were the most common complaints.
  • Each roentgenologist who reviewed the films noted a very unusual incidence of enlargement of the heart, which the authors thought was probably compensatory.
  • Physicians in the workers' communities stated that they did not find an unusual amount of tuberculosis among these workers.
  • Aside from plant E, the authors judged that the dust hazard was not excessive except in the preparation rooms of plants B and C.
  • In plant B, 6 of 36 death claims and 8 of 10 permanent and total disability claims were listed as due to pulmonary tuberculosis. On individual review, the authors judged the investigated deaths to be uncomplicated tuberculosis. Among the disability claims, 1 was uncomplicated tuberculosis and 2 were uncomplicated asbestosis put on disability because of a mistaken diagnosis of tuberculosis.
  • An experimental exhaust installation in one department of plant C reduced dust by 50 percent, based on comparative dust counts.
• The authors' conclusion: The authors concluded that prolonged exposure to asbestos dust caused a pulmonary fibrosis different from silicosis and demonstrable on X-ray films, which, from this study, appeared clinically milder than silicosis. They also concluded that cardiac enlargement was frequently associated with asbestosis, that a predisposition to tuberculosis was not indicated, that no case showed marked disability, that dust standards could not yet be set, and that dust in the plants could be substantially reduced.
• Limitations the authors state:
  • Workers had moved between departments and plants, and dust was measured only at the time of the survey, so individual cases could not be correlated with definite amounts of dust exposure.
  • Small numbers made it impossible to determine how far age contributed to the rise in positive diagnoses with years of exposure.
  • The death claims were too few to support reliable conclusions from any subdivision of the figures.
  • An influenza epidemic in late 1928 and early 1929 affected the comparison of respiratory disease claims.
  • Dust counts included non-asbestos material, mainly cotton, so actual asbestos dust exposure was considerably less than the counts indicate.
  • Whether workers classed as doubtful were progressing toward definite asbestosis could not yet be known.
  • This was a preliminary report, and a more extensive study was under way.

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, Silicosis.

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