Reply to Dr. Dunnigan. Chrysotile as a mesothelial carcinogen in man

Our plain-English summary of Reply to Dr. Dunnigan. Chrysotile as a mesothelial carcinogen in man, by A. Churg (American Journal of Industrial Medicine, 1988).

The study

• Author: A. Churg
• Journal: American Journal of Industrial Medicine
• Published: 1988;14(2):235-8
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

In this letter, Churg replied to a commentary by Dr. Dunnigan (1988) about whether chrysotile asbestos causes mesothelioma in humans and how studies of lung mineral content should be interpreted. Drawing on his own recent review, Churg reported finding 53 cases in which a reasonable argument could be made that mesothelioma was caused by chrysotile. Of these, 41 occurred in people exposed to chrysotile ore, usually through mining and milling, 10 in chrysotile factory workers, and 2 in other settings. In 11 of these cases, mineral analysis of lung tissue found only chrysotile ore components (chrysotile and tremolite). In nine Quebec miners and millers with mesothelioma, the median chrysotile plus tremolite lung burden was about three times that of exposure-period matched miners and millers with asbestosis. It was more than two orders of magnitude greater than the amphibole content in shipyard workers with mesothelioma. Churg argued that chrysotile is a weak mesothelial carcinogen that requires very high exposure, rather than a non-carcinogen. He also argued that low chrysotile lung content may poorly reflect exposure, because chrysotile does not accumulate readily in the lung. He described tremolite as the possible causal agent as consistent with the data but not established, and he declined to comment on legal cases. He concluded that amosite and crocidolite are much more potent, but extremely large doses of chrysotile can produce mesothelioma.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This letter to the editor replied to a commentary by Dr. Dunnigan on whether chrysotile asbestos causes mesothelioma in humans. It reported no new study, summarizing instead the author's earlier review and lung analyses. That review found 53 cases in which a reasonable argument could be made that a mesothelioma was caused by chrysotile. Of these, 41 involved chrysotile ore exposure, usually from mining and milling, and 10 involved chrysotile factory workers. In 11 of the 53 cases, lung analysis found only chrysotile ore components (chrysotile plus its natural contaminant tremolite). In an earlier comparison, nine Quebec chrysotile miners and millers with mesothelioma had a median chrysotile plus tremolite lung burden about three times that of miners and millers with asbestosis. The author concluded that the published data were consistent with the notion that, although amosite and crocidolite are much more potent, extremely large doses of chrysotile, with whatever tremolite accompanies it, can produce mesothelioma. The author judged the idea that tremolite is the real cause consistent with the data but unestablished, as the number of cases is very small.

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: Letter to the editor (reply to a commentary), summarizing the author's own earlier review and published lung mineral analyses; no new study
• Who was studied: No new population. The letter refers to 53 possible chrysotile-induced mesothelioma cases from the author's earlier review, and to a comparison of nine Quebec chrysotile miners and millers with mesothelioma against exposure-period matched miners and millers with asbestosis
• Exposure: Chrysotile asbestos, including chrysotile ore with its tremolite contaminant (mining and milling) and processed chrysotile products, contrasted with the amphiboles amosite and crocidolite
• Main results:
  • The author's earlier review found 53 cases in which a reasonable argument could be made that a mesothelioma was caused by chrysotile
  • Of the 53 cases, 41 were in people exposed to chrysotile ore, usually from mining and milling, and 10 were in chrysotile factory workers
  • In 11 of the 53 cases, mineral analysis of lung tissue found only chrysotile ore components (chrysotile plus tremolite)
  • Among Quebec chrysotile miners and millers, the median chrysotile plus tremolite lung burden in the nine with mesothelioma was about three times the median in the matched group with asbestosis
  • Lung fiber content in the chrysotile-exposed mesothelioma cases was more than two orders of magnitude greater than the amphibole content in shipyard workers with mesothelioma and amphibole (amosite and crocidolite) exposure
• The authors' conclusion: The author concluded that the published data are consistent with amosite and crocidolite being much more potent mesothelial carcinogens, while extremely large doses of chrysotile, with whatever tremolite accompanies it, can produce mesothelioma in man. The author also stressed a distinction between "no" effect and "little" effect
• Limitations the authors state:
  • The number of cases behind these conclusions, especially cases with lung mineral analysis, is very small
  • Frequent co-exposure to both chrysotile and amphibole makes the question hard to study
  • The chrysotile content of the lung may be a very poor marker of how much chrysotile a person was exposed to
  • The role of tremolite is not established, and no study of a tremolite-free chrysotile mine has been reported

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Chrysotile, Mesothelioma, Tremolite, Amphibole Group, Amosite, Crocidolite.

Related studies

• Obfuscation: a reply to Dr. Dunnigan — D.E. Lilienfeld (1988)
• On Dr. Dunnigan's commentary linking chrysotile asbestos with mesothelioma — M.R. Becklake (1988)
• Response to Dr. Dunnigan's commentary. The role of chrysotile in the pathogenesis of mesothelioma — J.M. Craighead (1988)
• On the statement by Jacques Dunnigan — J.M. Davis (1988)
• Continuous exposure to chrysotile asbestos can cause transformation of human mesothelial cells via HMGB1 and TNF-α signaling — F. Qi, G. Okimoto, et al. (2013)
• Chromosomal changes induced by chrysotile fibres or benzo-3,4-pyrene in rat pleural mesothelial cells — M.C. Jaurand, L. Kheuang, et al. (1986)

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