Asbestos and carcinogenicity

Our plain-English summary of Asbestos and carcinogenicity, by J.C. McDonald, A.D. McDonald (Science, 1990).

The study

• Authors: J.C. McDonald, A.D. McDonald
• Journal: Science
• Published: 1990;249(4971):844
• Type of article: Comment, Letter
• Cited by: 15 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. 003815).

Summary of the article

In this letter, the authors responded to a letter by William J. Nicholson et al. (Science, 18 May). That letter had alleged that there had been 67 or more cases of mesothelioma among Quebec chrysotile miners and millers, and attributed the estimate to J. C. McDonald. The authors stated that their cohort was 11,379 persons born between 1891 and 1920 and employed for 1 month or more. By the end of 1975 the cohort had 11 mesothelioma cases among 4,547 deaths, and 18 cases were known by 1978. A follow-up to 1990 was nearly complete. More than 70% of the cohort had died, and a subsample study suggested the eventual number of cases may be about 30. At least seven of these cases had been exposed to crocidolite in a small local factory, and one had substantial amosite exposure. Citing Montana tremolite data, the authors suggested that the remaining cases might possibly be attributed to fibrous tremolite contamination, roughly estimated at about 1.5%. They contrasted this with crocidolite-exposed gas mask and cigarette filter workers, in whom 16 to 19% of all deaths were attributed to mesothelioma. They defended well-controlled lung fibre studies and argued that the amphibole hypothesis concerns mesothelioma, not lung cancer. They cited textile plants where a chrysotile-only plant had one mesothelioma case, against 12 and 14 or more in mixed-exposure plants. They concluded that spending billions of dollars to control a minuscule or nonexistent risk seemed strange and sad.

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

In this letter to the editor of Science, not a new study, the authors replied to Nicholson and colleagues about mesothelioma in Quebec chrysotile miners and millers. Citing earlier work, they reported 11 mesothelioma cases among 4,547 deaths to the end of 1975 in a cohort of 11,379 people born 1891 to 1920 and employed at least 1 month, and 18 known cases by 1978. They estimated the eventual total might be about 30. At least seven cases had crocidolite exposure in a small local factory; one had substantial amosite exposure. They suggested the rest might be due to tremolite contamination, adding that no one knows for certain. Citing other studies, they argued that workers exposed only to commercial chrysotile suffered much less mesothelioma than crocidolite-exposed workers. They stated that residents of the Quebec mining towns, exposed to chrysotile levels far above those in public buildings, had few if any mesothelioma cases due to nonoccupational exposure. They called it strange and sad that a country should spend billions of dollars on questionable control of what they termed a minuscule or nonexistent health risk.

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 (correspondence) replying to an earlier letter by Nicholson et al.; not an original study
• Who was studied: The authors' previously published cohort of 11,379 Quebec chrysotile mining and milling workers, born between 1891 and 1920 and employed for 1 month or more
• Exposure: Chrysotile mining and milling in Quebec. Some cohort members were also exposed to crocidolite or amosite, and the chrysotile contained fibrous tremolite contamination roughly estimated at about 1.5%
• Main results:
  • In the Quebec cohort (citing the authors' earlier work), there were 11 cases of mesothelioma among 4,547 deaths to the end of 1975
  • By 1978 the authors knew of 18 mesothelioma cases in the cohort
  • More than 70% of the cohort had died. Based on a subsample, the authors estimated the eventual number of mesothelioma cases may be about 30
  • At least seven of the mesothelioma cases had been exposed to crocidolite in a small local factory
  • One of the mesothelioma cases had substantial exposure to amosite
  • The authors suggested it seemed possible that the remaining cases could be attributed to fibrous tremolite contamination (roughly estimated at about 1.5%). They based this on exposure-response data from studies of Montana miners and millers exposed only to tremolite
  • Citing other studies, the authors stated that 16 to 19% of all deaths among workers exposed to crocidolite in gas mask filter or cigarette filter manufacture were attributable to mesothelioma
  • The authors stated that workers exposed only to commercial chrysotile had suffered much less mesothelioma than those crocidolite-exposed workers
  • The authors stated that in the general population of the Quebec chrysotile mining towns, exposed over generations to chrysotile concentrations far greater than anything encountered in public buildings, there had been few if any cases of mesothelioma attributable to nonoccupational exposure
  • The authors stated that, in well-controlled lung tissue studies cited in the letter, the concentration of amphibole fibers, but not chrysotile fibers, in patients with mesothelioma consistently exceeded that of controls
  • In cited studies of asbestos textile plants, the chrysotile-only plant had virtually the same lung cancer exposure-response curve as the two mixed-exposure plants. It had only one mesothelioma case, compared with 12 in one mixed-exposure plant and 14 or more in the other
• The authors' conclusion: The authors concluded that, whether or not chrysotile itself can cause mesothelioma, workers exposed only to commercial chrysotile suffered much less from it than crocidolite-exposed workers. They called it strange and sad that a country (not named in the letter) should commit billions of dollars to the questionable control of what they described as a minuscule or nonexistent health risk; the letter does not spell out which control measures it means
• Limitations the authors state:
  • The authors stated that no one knows how many of the many thousand people employed in the Quebec chrysotile industry have died, or how many of those deaths were from mesothelioma
  • The authors stated that no one knows for certain whether the remaining cases could be attributed to tremolite contamination
  • The authors noted that they had urged caution in interpreting lung tissue fiber studies unless those studies are carefully controlled

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Quebec Chrysotile, Crocidolite, Amosite, Tremolite, Tremolite Contamination, amphibole hypothesis, Lung Cancer.

Related studies

• Adverse health effects of asbestos: solving mysteries regarding asbestos carcinogenicity based on follow-up survey of a Chinese factory — E. Yano (2018)
• The epidemiology of mesothelioma in historical context — J.C. McDonald, A.D. McDonald (1996)
• The 1891-1920 birth cohort of Quebec chrysotile miners and millers: development from 1904 and mortality to 1992 — F.D. Liddell, A.D. McDonald, et al. (1997)
• The 1891-1920 birth cohort of Quebec chrysotile miners and millers: mortality 1976-88 — J.C. McDonald, F.D. Liddell, et al. (1993)
• Chrysotile, tremolite, and mesothelioma — J.C. McDonald, A.D. McDonald (1995)
• Reply to letter by Nolan and colleagues--re: the carcinogenicity of New York state talc dusts in humans — M. Finkelstein (2013)

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