Incidence of mesothelioma and asbestosis by occupation in a diverse workforce

Our plain-English summary of Incidence of mesothelioma and asbestosis by occupation in a diverse workforce, by N.L. DeBono, H. Warden, C. Logar-Henderson, et al (American Journal of Industrial Medicine, 2021).

The study

• Authors: N.L. DeBono, H. Warden, C. Logar-Henderson, S. Shakik, M. Dakouo, J. MacLeod, P.A. Demers
• Journal: American Journal of Industrial Medicine
• Published: 2021;64(6):476-487
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: We sought to characterize detailed patterns of mesothelioma and asbestosis incidence in the workforce as part of an occupational disease surveillance program in Ontario, Canada.

Methods: The Occupational Disease Surveillance System (ODSS) cohort was established using workers' compensation claims data and includes 2.18 million workers employed from 1983 to 2014. Workers were followed for mesothelioma and asbestosis diagnoses in Ontario Cancer Registry, physician, hospital, and ambulatory care records through 2016. Trends in incidence rates were estimated over the study period. Cox proportional hazard models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: A total of 854 mesothelioma and 737 asbestosis cases were diagnosed during follow-up. Compared with all other workers in the ODSS, those employed in construction trades occupations had the greatest adjusted incidence rate of both mesothelioma (223 cases; HR, 2.38; 95% CI: 2.03-2.78) and asbestosis (261 cases; HR, 3.64; 95% CI: 3.11-4.25). Rates were particularly elevated for insulators, pipefitters and plumbers, and carpenters. Workers in welding and flame cutting, boiler making, and mechanic and machinery repair occupations, as well as those in industrial chemical and primary metal manufacturing industries, had strongly elevated rates of both diseases. Rates were greater than anticipated for workers in electrical utility occupations and education and related services.

Conclusions: Results substantiate the risk of mesothelioma and asbestosis in occupation and industry groups in the Ontario workforce with known or suspected asbestos exposure. Sustained efforts to prevent the occurrence of additional cases of disease in high-risk groups are warranted.

© 2021 Wiley Periodicals LLC.

In plain English

The authors used Ontario, Canada's workers' compensation-based Occupational Disease Surveillance System to compare mesothelioma and asbestosis rates across jobs and industries. It followed 2.18 million workers with claims from 1983 to 2014 for mesothelioma (cancer registry, 1983 to 2016) and 1.76 million for asbestosis (physician, hospital and ambulatory care records, 1999 to 2016). Each group was compared with all other workers in the cohort. There were 854 mesothelioma and 737 asbestosis cases. Among broad occupation groups, construction trades workers had the highest adjusted rates compared with the rest of the cohort: hazard ratio 2.38 (95% CI 2.03 to 2.78) for mesothelioma and 3.64 (3.11 to 4.25) for asbestosis. Within construction trades, insulators had the largest hazard ratios: 25.82 for mesothelioma (95% CI 15.2 to 43.8; 14 cases) and 35.2 for asbestosis (95% CI 21.7 to 57.0; 17 cases). Rates were also elevated for pipefitters and plumbers and in electric power utilities. The authors concluded that the results substantiate asbestos-related disease risk in specific Ontario worker groups. They noted that each worker's job was recorded at only one point in time, without individual exposure information.

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: Retrospective cohort study for occupational disease surveillance. It linked workers' compensation claims to cancer registry and health administrative records. Hazard ratios were estimated with Cox proportional hazards models adjusted for age, birth year and sex. Each occupation or industry group was compared with all other workers in the cohort.
• Who was studied: Workers in Ontario, Canada, with an accepted lost-time workers' compensation claim between 1983 and 2014. These were mostly claims for trauma and musculoskeletal injuries, and 66% of workers were male. A total of 2.18 million were followed for mesothelioma (1983 to 2016) and a subcohort of 1.76 million were followed for asbestosis (1999 to 2016).
• Exposure: Occupation and industry at the time of the compensated injury, as coded by the Workplace Safety and Insurance Board, across hundreds of occupation and industry groups. There were no individual asbestos exposure measurements, and the article does not specify fiber types.
• Main results:
  • Overall, 854 incident cases of mesothelioma and 737 cases of asbestosis were identified during follow-up.
  • Construction trades occupation division, compared with all other cohort workers. Asbestosis: 261 cases among 181,392 workers, HR 3.64 (95% CI 3.11 to 4.25). Mesothelioma: 223 cases among 216,117 workers, HR 2.38 (95% CI 2.03 to 2.78).
  • Insulating occupations, construction. Asbestosis: 17 cases among 1140 workers, HR 35.2 (95% CI 21.7 to 57.0). Mesothelioma: 14 cases among 1347 workers, HR 25.82 (95% CI 15.2 to 43.8).
  • Pipefitting, plumbing and related occupations. Asbestosis: 70 cases among 14,684 workers, HR 8.18 (95% CI 6.38 to 10.48). Mesothelioma: 57 cases among 17,001 workers, HR 5.88 (95% CI 4.49 to 7.71).
  • Workers at firms classified as asbestos mines. Asbestosis: 5 or fewer cases among 38 workers, HR 25.4 (95% CI 3.6 to 181.8). Mesothelioma: 8 cases among 41 workers, HR 240.4 (95% CI 119 to 483). The authors noted these estimates were based on relatively few cases.
  • Electric power, gas, and water utilities industry. Asbestosis: 38 cases among 19,188 workers, HR 3.67 (95% CI 2.65 to 5.09). Mesothelioma: 25 cases among 22,417 workers, HR 2.17 (95% CI 1.45 to 3.23).
  • Education and related services industry. Asbestosis: 48 cases among 84,527 workers, HR 1.57 (95% CI 1.17 to 2.10). Mesothelioma: 44 cases among 98,982 workers, HR 1.32 (95% CI 0.97 to 1.79); this confidence interval includes 1.
  • Universities and colleges. Asbestosis: 10 cases among 11,926 workers, HR 2.14 (95% CI 1.15 to 4.00). Mesothelioma: 12 cases among 14,273 workers, HR 2.32 (95% CI 1.31 to 4.10).
  • Mesothelioma trends: age-standardized rates suggested a plateau in the high-risk occupation groups as of 2005, while the rest of the cohort had a modest increase over follow-up. The trend figure covers males, 1995 to 2015.
  • Asbestosis trends: incidence rates and total case counts declined during each period of follow-up.
• The authors' conclusion: The authors concluded that their results provide evidence substantiating the risk of asbestos-related disease among Ontario workers in specific occupation and industry subgroups. They also concluded that sustained prevention efforts and continued surveillance are warranted.
• Limitations the authors state:
  • The study lacked complete work histories and individual-level exposure information.
  • Occupation and industry were recorded at a single time point. The authors considered misclassification of exposure group likely common, which would bias estimates toward no effect.
  • The comparison group included many workers in high-hazard industries with elevated baseline risk. The authors said this likely made the estimates smaller than a comparison with the general population would.
  • Excluding cases diagnosed before follow-up began may have underestimated associations in well-recognized high-risk groups.
  • The cohort consisted mainly of workers compensated for musculoskeletal injuries, which could introduce selection bias.
  • Physician billing coding practices may have led to asbestosis cases being missed.
  • Results for females were not shown because they were based on few cases: 65 of mesothelioma and 56 of asbestosis.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Occupational Disease, Cancer Registry, Incidence, Hazard Ratio, confidence interval, Insulator, Pipefitter.

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• Women's occupation and cancer: preliminary analysis of cancer registrations in England and Wales, 1971-1990 — J. Simpson, E. Roman, et al. (1999)
• Feasibility of identifying high-risk occupations through tumor registries — M.D. Whorton, J. Schulman, et al. (1983)
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