Tremolite, other amphiboles, and mesothelioma

Our plain-English summary of Tremolite, other amphiboles, and mesothelioma, by J.C. McDonald (American Journal of Industrial Medicine, 1988).

The study

• Author: J.C. McDonald
• Journal: American Journal of Industrial Medicine
• Published: 1988;14(2):247-9
• Type of article: Letter
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000252).

In plain English

This is a letter to the editor, not a full research report, replying to a paper by Dr. Jacques Dunnigan on chrysotile asbestos and mesothelioma. The author described two surveys by the author's group that were completed but unpublished, giving no detailed figures. In the first, lung tissue taken after death from nearly 200 former Quebec chrysotile miners and millers and South Carolina chrysotile textile workers held many times more chrysotile and tremolite fibers in the miners' and millers' lungs. The author wrote that this did not explain why lung cancer mortality (SMR) was five times higher in South Carolina, and speculated about another textile-industry factor such as sprayed mineral oil. In the second, about eighty mesothelioma cases and matched referents from across Canada (excluding British Columbia) who died in 1980-84 were compared. Long amphibole fibers strongly separated cases from referents, while chrysotile fibers on their own did not significantly do so. Long tremolite fibers contributed importantly, and some of them may come from chrysotile contamination. The author warned that lung fiber studies have limitations. The author concluded that most studies suggest amphiboles are mainly responsible for mesothelioma, and called for further research on tremolite.

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• Design: Letter to the editor (commentary) reporting, in brief, results of two completed but unpublished lung-tissue surveys by the author's group
• Who was studied: Survey 1: postmortem lung tissue from nearly 200 deceased members of a Quebec chrysotile miner and miller cohort and a South Carolina chrysotile textile worker cohort. Survey 2: about eighty mesothelioma cases and individually matched referents from across Canada (excluding British Columbia), from deaths in 1980-84.
• Exposure: Fibers found in lung tissue by electron microscopy: chrysotile and amphiboles, including tremolite. Long and short fibers were analysed separately.
• Main results:
  • Survey 1: the Quebec chrysotile miners and millers had many times more chrysotile and tremolite fibers in their lungs than the South Carolina textile workers.
  • The author wrote that this lung-fiber difference did not explain the lung cancer SMR being five times higher in South Carolina than in Quebec. The author speculated about another factor in the textile industry, such as sprayed mineral oil.
  • Survey 2 (Canadian mesothelioma cases vs matched referents): long amphibole fibers strongly distinguished cases from referents, and shorter fibers added no information.
  • Survey 2: chrysotile fibers by themselves gave no statistically significant distinction between cases and referents.
  • Survey 2: long tremolite fibers made up an important part of the amphibole contribution. The author suggested some, but not all, of this tremolite may represent chrysotile contamination.
• The authors' conclusion: The author agreed with Dr. Dunnigan that most epidemiological studies, including lung burden studies, suggest amphiboles are mainly responsible for mesothelioma. In the author's view, the fact that some tremolite may come with industrial chrysotile does not change this. The author said much further research is needed on how many mesothelioma cases fibrous tremolite causes and from which sources.
• Limitations the authors state:
  • Fibers found in lung tissue at death do not necessarily reflect past exposure, because amphibole fibers are retained more readily and for much longer than chrysotile.
  • Lung tissue studies depend on postmortem and surgical material, which is open to selection bias, and they need similar tissue from comparable referents.
  • Fibers are not evenly spread through the lung, and investigators seldom, if ever, account for this source of error.
  • What lung fibers at death mean depends on how fibers cause cancer, which is not known. The author therefore regarded lung burden studies as one element of the evidence, not necessarily outweighing other evidence.

Topics

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

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

Related studies

• Cohort study of mortality of vermiculite miners exposed to tremolite — J.C. McDonald, A.D. McDonald, et al. (1986)
• Radiological survey of past and present vermiculite miners exposed to tremolite — J.C. McDonald, P. Sebastien, et al. (1986)
• Health of vermiculite miners exposed to trace amounts of fibrous tremolite — J.C. McDonald, A.D. McDonald, et al. (1988)
• Chrysotile, tremolite, and malignant mesothelioma in man — A. Churg (1988)
• Mesothelioma in Cyprus: the role of tremolite — K. McConnochie, L. Simonato, et al. (1987)
• Association of Metsovo lung and pleural mesothelioma with exposure to tremolite-containing whitewash — A.M. Langer, R.P. Nolan, et al. (1987)

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