Biologic Response To Kind And Amount Of Asbestos

Our plain-English summary of Biologic Response To Kind And Amount Of Asbestos, by M. Kleinfeld (1973).

The study

• Author: M. Kleinfeld
• Published: Journal Of Occupational Medicine 15(3):296-300, March (1973)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 001306. The article is still under copyright, so we describe it here rather than post it.

In plain English

This article was a review, not a new study. The author summarized research on how the kind and amount of inhaled asbestos relate to asbestosis, lung cancer, mesothelioma and pleural calcification. The review described general agreement that all commercial forms of asbestos can cause lung fibrosis. It cited studies linking risk to amount of exposure. These included a report by Enterline and colleagues that respiratory cancer mortality rose with cumulative chrysotile exposure. They also included a study of pipe coverers by Murphy and colleagues in which no asbestosis was found below 60 mppcf-years, a measure of cumulative dust exposure. It described unpublished work by the author and colleagues on talc workers exposed to tremolite and anthophyllite, which found one case of pneumoconiosis among 39 workers. On fiber type, it reported that anthophyllite had rarely been linked to mesothelioma and that fiber shape and diameter may matter. It stated there was no evidence that pleural plaques relate to mesothelioma. The author concluded it was difficult to rank asbestos types by relative harm. The author noted that most industrial exposures were to mixed asbestos types, and that most studies suggesting differences between types lacked quantitative data on cumulative exposure, fiber characteristics and cofactors.

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• Design: Narrative review of published and unpublished studies, both human and animal, on the effects of different types and amounts of asbestos
• Who was studied: No new population was studied. The review drew mainly on studies of occupationally exposed groups (insulation workers, pipe coverers, textile workers, miners and millers, talc workers), plus animal experiments.
• Exposure: Crocidolite, chrysotile and amosite, or mixtures of them; also anthophyllite, and commercial talc containing tremolite and anthophyllite. Exposure amounts were expressed in reviewed studies as mppcf, mppcf-years and fibers/ml.
• Main results:
  • The review reported general agreement that all forms of asbestos in commercial use can produce fibrotic effects in the lungs.
  • In the cited study of pipe coverers exposed to amosite and chrysotile (Murphy, Ferris, Burgess et al.), no asbestosis was found in men exposed to less than 60 mppcf-years.
  • In unpublished work by Kleinfeld, Messite and Langer, only one case of pneumoconiosis was found among 39 workers exposed to commercial talc containing tremolite and anthophyllite. Their mean exposure was 16.2 years, with a time-weighted average of 23.0 mppcf.
  • In a comparison of talc workers at two plants by the same authors, workers with four times the mean fiber count had a significantly increased prevalence of pneumoconiosis. The review described this as indicating a dose-response relationship.
  • Enterline, DeCoufle and Henderson were cited for an exposure-response relationship between chrysotile and respiratory disease. The respiratory cancer standardized mortality ratio, printed as 1667 for minimal exposures and 5556 for cumulative exposures above 750 mppcf-years, increased with exposure.
  • The review noted that, despite a thorough search, no mesotheliomas had been associated with anthophyllite asbestos production in Finland.
  • In a cited mortality study of talc workers exposed to talc and tremolite (Kleinfeld, Messite, Kooyman et al.), there was an excess of deaths from cancer of the lung and pleura.
  • The review stated there was no evidence that pleural plaques bear any relation to the development of mesothelioma.
• The authors' conclusion: The author concluded that it is difficult to grade different types of asbestos by relative pathogenicity for either asbestosis or cancer. The author also concluded that fiber shape and size appear to be significant factors, and that cofactors such as trace metals cannot be excluded.
• Limitations the authors state:
  • The author stated that industrial exposures are usually to a mixture of asbestos types, which impedes comparison of fiber types in humans.
  • The author stated that animal studies use doses far larger than human exposures, so animal data cannot support firm conclusions about humans.
  • The author stated that most epidemiological studies that appear to show differences between asbestos types lack quantitative data on cumulative exposure, fiber characteristics and cofactors.

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer, Mesothelioma, Pleural Calcification, Fibrosis, Chrysotile, Insulator, Million Particles per Cubic Foot (mppcf), Talc.

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