The epidemiology of mesothelioma in historical context

Our plain-English summary of The epidemiology of mesothelioma in historical context, by J.C. McDonald, A.D. McDonald (The European Respiratory Journal, 1996).

The study

• Authors: J.C. McDonald, A.D. McDonald
• Journal: The European Respiratory Journal
• Published: 1996;9(9):1932-42
• Type of article: Historical article, Review
• Cited by: 164 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Primary malignant mesothelial tumours were recognized by pathologists before asbestiform minerals (chrysotile, crocidolite and amosite) were mined commercially. The discovery, 40 yrs ago, of a causal link with crocidolite and the wide-ranging epidemiological studies which followed are the subject of this review. Early case-control and descriptive surveys, supplemented by cohort studies in insulation workers and chrysotile miners, quickly demonstrated major occupational and geographical differences, with high risk in naval dockyard areas and in the heating trades. In the 1980s, reliable cohort surveys showed that in mining and in the manufacture of asbestos products the mesothelioma risk was much higher when exposure included crocidolite or amosite than chrysotile alone. However, qualitative and quantitative information on exposure was too often inadequate for this evidence to be conclusive. Well-controlled lung fibre analyses have reduced these deficiencies and demonstrated the probable implications of the greater biopersistence of amphibole fibres. Chrysotile for industrial use often contains low concentrations of fibrous tremolite, which may well explain the few cases of mesothelioma associated with this type of asbestos. Progress in this field has been much retarded by controversy, for which the 20 year gap between the availability of reliable estimates of risk for the mining of chrysotile and that for crocidolite or amosite may have been largely responsible.

In plain English

This article was a review by the authors of about 40 years of research on the epidemiology of mesothelioma. It covered case-control studies, incidence and mortality statistics, cohort mortality studies of asbestos miners, manufacturing workers and other groups, and studies measuring mineral fibres in lung tissue. In the mining cohorts reviewed, mesothelioma accounted for 47.3 and 39.0 per 1,000 deaths among crocidolite miners, compared with 4.5 and 4.7 per 1,000 among chrysotile miners. In product manufacture, rates were higher in cohorts with amphibole exposure. The authors noted that this measure is crude and that no cohort reliably assessed exposure to individual fibre types. They reported that, across six lung-fibre studies, amphibole fibres over 8 micrometres long could explain nearly all cases. In one Canadian lung-tissue study, perhaps 23 of 78 cases were estimated to be due to tremolite. The authors concluded that the main determinants of mesothelioma are reasonably clear. They suggested that tremolite contaminating commercial chrysotile may well explain the few cases associated with chrysotile, a hypothesis they said still needed testing.

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 epidemiological studies of mesothelioma
• Who was studied: published case-control studies, incidence and mortality analyses, cohort mortality studies (miners and millers, asbestos product manufacturers, insulation workers, gas-mask and filter workers, dockyard workers) and lung fibre burden studies, from the 1960s to the mid-1990s
• Exposure: chrysotile, crocidolite, amosite and fibrous tremolite (including tremolite contaminating chrysotile); erionite and man-made mineral fibres were also discussed
• Main results:
  • In a reviewed case-control study of 344 male mesothelioma cases in Canada (1960 to 1972) and the USA (1972), insulation work showed the highest relative risk, 46.1
  • In the mining and milling cohorts reviewed, mesothelioma proportional mortality per 1,000 deaths was 4.5 (Quebec, chrysotile), 4.7 (Italy, chrysotile), 6.2 (South Africa, amosite), 47.3 (South Africa, crocidolite), 39.0 (Australia, crocidolite) and 24.2 (USA, tremolite). The authors judged that crocidolite carries a much higher risk than chrysotile, with amosite and tremolite probably in between
  • In manufacturing cohorts, mesothelioma proportional mortality per 1,000 deaths, with versus without amphibole exposure, was 20.7 versus 3.5 in cement workers, 14.8 versus 2.5 in textile workers, and 5.4 versus 0 in friction product workers
  • Across six reviewed lung fibre burden studies, amphibole fibres over 8 micrometres long could have explained nearly all cases, and shorter fibres few if any
  • In a Canadian lung-tissue case-control study of 78 mesothelioma deaths (1980 to 1984), multivariate analysis suggested that perhaps 23 of the 78 cases were due to tremolite
  • In the Quebec chrysotile cohort, mesothelioma incidence was about 2.5 times greater among miners and millers at Thetford Mines than at Asbestos, where lung tremolite concentrations were 2 to 4 times lower
  • Backward extrapolation of mortality trends suggested that, before rates in males and females diverged, mesothelioma mortality was about 1 to 2 per million in both sexes
• The authors' conclusion: The authors concluded that the main determinants of mesothelioma are reasonably clear. They suggested that low-level tremolite contamination of industrial chrysotile may well explain the few mesothelioma cases associated with chrysotile, and that controversy had slowed progress in the field.
• Limitations the authors state:
  • In none of the cohort studies could exposure to individual fibre types be reliably assessed
  • Proportional mortality rates are a crude indicator of risk because they do not account for exposure levels or competing causes of death
  • None of the six lung burden studies was wholly adequate in controlling for confounders
  • The tremolite hypothesis still required further analyses to test it

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Chrysotile, Crocidolite, Lung cancer, Mesothelioma, Tremolite.

Medical terms in this study, explained in our Lexicon: Epidemiology, Mesothelioma, Asbestiform, Chrysotile, Crocidolite, Amosite, Discovery, Insulator.

Related studies

• Epidemiology of malignant mesothelioma--an outline — J.C. McDonald (2010)
• A comparison of asbestos fiber potency and elongate mineral particle (EMP) potency for mesothelioma in humans — D.H. Garabrant, S.T. Pastula (2018)
• The epidemiology of mesothelioma — M. Britton (2002)
• Carving of non-asbestiform tremolite and the risk of lung cancer: a follow-up mortality study in a historical nephrite processing cohort — H.Y. Yang, R.H. Shie, et al. (2013)
• Pulmonary mineral fibers after occupational and environmental exposure to asbestos in the Russian chrysotile industry — A. Tossavainen, E. Kovalevsky, et al. (2000)
• Mesothelioma in Quebec chrysotile miners and millers: epidemiology and aetiology — A.D. McDonald, B.W. Case, et al. (1997)

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