Work-related mesothelioma in Québec, 1967-1990

Our plain-English summary of Work-related mesothelioma in Québec, 1967-1990, by R. Bégin, J.J. Gauthier, M. Desmeules, et al (American Journal of Industrial Medicine, 1992).

The study

• Authors: R. Bégin, J.J. Gauthier, M. Desmeules, G. Ostiguy
• Journal: American Journal of Industrial Medicine
• Published: 1992;22(4):531-42
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Prior surveys of malignant mesothelioma in Québec have noted that almost all the excess in occupational exposure related mesothelioma was in the manufacture and industrial application of asbestos rather than in the mining and milling operations. To evaluate the current status of malignant pleural mesothelioma in the Québec workforce, we reviewed all cases of pleural mesothelioma seen and accepted by the Québec Workman's Compensation Board (CSST) for work related compensation of industrial disease. We identified 120 cases, 7 of whom were females. They were of an average age of 59 +/- 8.5 yrs (sd) (range 42-84); they were exposed to asbestos dust in the workplace for an average of 26 +/- 14.3 yrs (range 0.5-50). The cases were subdivided into 3 groups according to workplace asbestos exposures. There were 49 cases originating in the mines and mills of the Québec Eastern Township region (primary industry, group 1), 50 cases from the manufacture and industrial application sector (secondary industry, group 2), and 21 cases from industries where asbestos was not a major work material, often an "incidental" material (tertiary industry, group 3). Group 1 was of an average age of 62 +/- 8 years, exposed to asbestos dust 31 +/- 14 years and the distribution of exposure time was as follows: 15% cases with < or = 10 year-exposure and 77% > or = 25 year-exposure. In group 2, the age was significantly lower at 57 +/- 9 years; the exposure time was also significantly lower at 22 +/- 14 years, and the distribution of exposure time differed from the above (29% cases with < or = 10 year-exposure and 48% > or = 25 year-exposure). In group 3, the average age was 58 +/- 7 years, the exposure time was also significantly lower at 28 +/- 12 years and the distribution of exposure time differed from the above (33% cases with < or = 10 year-exposure and 62% > or = 25 year-exposure). Analyses of the yearly incidence of new cases in each group documented the general incremental trend in all groups, with the sharpest rises in group 3. In the mining towns of Thetford and Asbestos, the incidence of mesothelioma was proportional to the workforce, thus suggesting that the tremolite air contamination, which is 7.5 x higher in Thetford, may not be a significant determinant of the disease in these workers.(ABSTRACT TRUNCATED AT 400 WORDS)

In plain English

The authors reviewed all 120 cases of pleural mesothelioma (113 men, 7 women) accepted as work-related by Québec's workers' compensation board (CSST) from 1967 to 1990. Cases were grouped by industry: 49 from the chrysotile mines and mills of Thetford and Asbestos, 50 from manufacturing, insulation and shipbuilding, and 21 from construction, maintenance and bystander work. Accepted cases rose over time in all groups, most sharply in the construction and maintenance group, which made up 33% of accepted cases in the last 4 years. Overall, 61% of cases had more than 25 years of exposure and 25% had less than 10 years. Short exposures were more common outside mining. The 20 Asbestos and 29 Thetford cases were in proportion to the two towns' workforces, although earlier measurements put tremolite levels 7.5 times higher at Thetford. The authors estimated 150-250 cases per million per year among the miners and millers in 1980-1990, above estimated North American rates. They concluded that tremolite may not be a determining factor in these chrysotile workers and that some cases could be chrysotile-induced.

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: Review of all work-related compensation cases accepted by a workers' compensation board (case series from administrative records), with comparisons between industry groups
• Who was studied: 120 cases of pleural mesothelioma (113 men, 7 women) accepted as work-related by the Québec Workman's Compensation Board (CSST), 1967 to 1990. All were diagnosed by open thoracotomy biopsy, and the pathology was reviewed by expert pathologists.
• Exposure: Workplace asbestos exposure in three groups. Group 1 (primary industry): the chrysotile mines and mills of the Eastern Townships (Asbestos and Thetford). Group 2 (secondary industry): manufacturing or daily handling of asbestos for insulation or shipbuilding. Group 3 (tertiary industry): occasional use, such as in construction or plumbing, or bystander exposure, such as maintenance workers and electricians. Average exposure was 26 years, with a range of 0.5 to 50 years. Earlier measurements cited by the authors found tremolite levels in air and lung tissue some 7.5 times higher at Thetford than at Asbestos.
• Main results:
  • The number of accepted work-related cases increased significantly over 1967 to 1990 (r = 0.8, p less than 0.001).
  • Of all 120 cases, 61% had more than 25 years of exposure and 25% had less than 10 years.
  • Group 1 (mines and mills, 49 cases) had an average age of 62 years and an average exposure of 30.5 years. Group 2 (50 cases) had an average age of 56.7 years and an average exposure of 21.4 years. Group 3 (21 cases) had an average age of 57.7 years and an average exposure of 27.7 years. Groups 2 and 3 differed significantly from group 1 in both age and exposure (p less than 0.05).
  • Cases with more than 25 years of exposure made up 76% of group 1, 46% of group 2 and 61% of group 3 (p less than 0.01).
  • Cases with less than 10 years of exposure made up 16% of group 1, 27% of group 2 and 33% of group 3, a significant difference.
  • Cases rose in every group, most sharply in group 3, which made up 33% of all accepted cases in the last 4 years of the study.
  • Group 1 included 20 cases from Asbestos and 29 from Thetford. The two subsets did not differ in age, exposure time or distribution of exposure duration. About 40% of the mining workforce came from Asbestos and 60% from Thetford, so the authors judged the incidence comparable relative to workforce size.
  • In the primary industry (group 1), cases occurred at about 2.5 per year in the last 10 years. This compares with 0.3 per year before 1969, as reported in earlier studies.
  • For 1980 to 1990, the authors estimated about 62.5 cases per million per year for the combined adult male population of the Asbestos and Thetford townships (some 40,000), and 150 to 250 cases per million per year for the chrysotile miners and millers. They described these rates as well below those estimated for the crocidolite mining townships of South Africa and well above North American rates.
• The authors' conclusion: The authors concluded that work-related mesothelioma increased in Québec over 1967 to 1990. They found the incidence among chrysotile miners and millers lower than in crocidolite workers but well above the North American male rate. They concluded that, comparing the two mining towns, tremolite contamination may not be a determining factor in these chrysotile workers, and that some cases may not necessarily be attributable to amphibole and could be chrysotile-induced. They also concluded that cases in the tertiary sector appear to be increasing more rapidly than in other sectors.
• Limitations the authors state:
  • Mesothelioma cases from before 1967 were not available for the review.
  • For group 3, the level of asbestos exposure could not be precisely determined from the records.
  • Yearly case counts fluctuate because of administrative and socioeconomic factors at the compensation board, so the data were also shown in 4-year periods.
  • Lung tissue fiber analyses had not yet been done on these cases. The authors planned them to further investigate whether the cases were chrysotile-induced.
  • The authors considered whether the rise in low-exposure cases could partly reflect publicity, a compassionate attitude of compensation board members, or greater awareness among physicians or next-of-kin. They judged it more likely to be a real increase in disease.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

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, Malignant Mesothelioma, Occupational Exposure, Pleural Mesothelioma, Asbestos Exposure, Tremolite.

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• Work-related respiratory disease in the United Kingdom, 1989-1992: report on the SWORD project — S.K. Meredith, J.C. McDonald (1994)
• Occupation and work-related ill-health in UK construction workers — S.J. Stocks, S. Turner, et al. (2011)
• SWORD '93. Surveillance of work-related and occupational respiratory disease in the UK — B.A. Sallie, D.J. Ross, et al. (1994)
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