Occupational cancer in Canada: what do we know?

Our plain-English summary of Occupational cancer in Canada: what do we know?, by K. Teschke, M.C. Barroetavena (CMAJ, 1992).

The study

• Authors: K. Teschke, M.C. Barroetavena
• Journal: CMAJ
• Published: 1992;147(10):1501-7
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

Objective: To examine the reporting of cases of occupational cancer in Canada in order to determine reporting requirements, the availability of data, the characteristics of reported cancers and the completeness of reporting.

Design: Descriptive epidemiologic study based on data requested from workers' compensation boards (WCBs) and cancer registries in each province and territory from 1980 to 1989.

Outcome Measures: The number of claims accepted and rejected by the WCBs; year of claim, cancer site, sex of claimant, age of claimant at diagnosis, occupation, industry, exposure agent and reasons for rejection of claims; and new primary cancers according to site, age and sex.

Results: Reporting of occupational cancer by physicians is required in Alberta, Saskatchewan and Newfoundland. Only British Columbia, Saskatchewan and Ontario were able to provide all the requested information about the claims. Of the 1026 claims in these three provinces almost all were by men, and about two-thirds were for cancers of the respiratory tract. Asbestos was listed as the etiologic agent in more than one-third of the cases. A comparison of the proportion of incident cancers accepted as occupational by the WCBs with the estimated proportion of cancers in the general population attributable to occupation (based on population-attributable risk percentages from epidemiologic data) suggests that less than 10% of occupational cancers [corrected] are compensated. The main source of the deficit is underreporting to WCBs rather than rejection of claims.

Conclusions: The availability of data about occupational cancers in Canada is inconsistent from jurisdiction to jurisdiction, and reporting is incomplete. An active disease surveillance system and additional education of physicians and workers about work-related illnesses may be required to improve reporting.

In plain English

This descriptive study asked Canada's provincial and territorial workers' compensation boards (WCBs) and cancer registries for 1980 to 1989 data on cancer claims and new cancers. Only Alberta, Saskatchewan and Newfoundland required physicians to report occupational disease; in Alberta and Saskatchewan this meant "notifiable" diseases, including certain cancers. Only British Columbia, Saskatchewan and Ontario could supply all the claim details requested. Those three provinces had 1026 cancer claims, and 97.5% were made by men. Of the 677 claims with exposure data, asbestos was the agent listed in 36%. Among men there, less than 0.25% of new cancers (excluding nonmelanoma skin cancer) were accepted as work-related. The lowest cited estimate of cancer due to occupation was 2%. Pleural cancer came closest to published estimates; lung and bladder cancer fell far short. The authors concluded that compensated cases were less than 10% of the number expected. They attributed this mainly to too few claims, not rejections, and said active surveillance and education of physicians and workers may be required. They cautioned that estimates from the United States and England may not fit Canada.

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: Descriptive epidemiologic study using data requested from workers' compensation boards, medical associations and cancer registries, compared with published estimates of the proportion of cancer attributable to occupation (population-attributable risk percentages)
• Who was studied: Cancer compensation claims processed by the WCBs of each Canadian province and territory, and new primary cancers recorded by provincial cancer registries, 1980 to 1989. Eight jurisdictions supplied claims data, but only British Columbia, Saskatchewan and Ontario (about 53% of the Canadian population) gave complete data. Those three provinces had 1026 claims. The comparison with registry cancers used men only and excluded nonmelanoma skin cancer.
• Exposure: Occupational exposures cited in cancer claims. Asbestos was listed in 36% of the 677 claims with exposure data. Ionizing radiation, sinter plant emissions, silica and polycyclic aromatic hydrocarbons were each listed in 5% to 10%. Occupations cited included miners, insulators, pipefitters or plumbers, electricians, carpenters and others.
• Main results:
  • Only three provinces (Alberta, Saskatchewan and Newfoundland) required physicians to report occupational disease.
  • According to a Table 1 footnote, the reporting legislation in Alberta and Saskatchewan covers "notifiable" occupational diseases, including certain types of cancer, rather than occupational disease in general.
  • Eight jurisdictions could supply data on occupational cancer claims, but only three provinces could retrieve all the requested data.
  • Annual cancer claims ranged from 1.2 per million people employed (New Brunswick) to 64.5 per million (Yukon Territory), with an overall mean of 15.7.
  • Of the 1026 claims in British Columbia, Saskatchewan and Ontario, 97.5% were made by men.
  • In these three provinces, claims were accepted less often for women than for men (17% versus 55%).
  • Saskatchewan accepted 83% of its claims, British Columbia 62% and Ontario 52%.
  • Claims for cancers of the lung and pleura were the most frequent and were more often accepted than rejected.
  • Of the 924 claimants with an occupation coded, miners were the largest group (23%).
  • Nonmelanoma skin cancer was excluded from the comparison with registry cancers, because some provinces' incidence figures did not include it.
  • In British Columbia, Saskatchewan and Ontario, less than 0.25% of all incident cancers in men were accepted by the WCBs as occupationally related. This figure excludes nonmelanoma skin cancer. The lowest estimate of cancer due to occupation the authors cited (Doll and Peto) was 2%.
  • Pleural cancer in men had the highest proportion of incident cases accepted. In British Columbia, 71 of 196 cases (36.7%) were accepted, against an estimated 47 to 76% attributable to occupation.
  • In Ontario, 78 of 316 incident pleural cancer cases in men (24.7%) were accepted for compensation.
  • The proportion of accepted claims for lung cancer in men was four or more times lower than the lowest published estimate of lung cancer due to occupation. Accepted proportions were 0.15% in British Columbia, 0.43% in Saskatchewan and 0.76% in Ontario, against estimates of 3 to 17%.
  • In Ontario, asbestos was listed for only 19% of lung cancer claims in which an exposure agent was recorded. The authors took this as suggesting underreporting of asbestos-related lung cancer in that province.
  • The proportion of accepted claims for bladder cancer was much lower than the published estimates for at-risk occupations.
  • The number of occupational cancer cases compensated in the three provinces was less than 10% of the number expected from epidemiologic data.
  • Underreporting to the WCBs, rather than rejection of claims, was responsible for most of the shortfall. The rejection rate for occupational disease claims in this study was 46%.
• The authors' conclusion: The authors concluded that the availability of occupational cancer data in Canada was inconsistent from jurisdiction to jurisdiction and that reporting was incomplete. They said more active occupational disease surveillance, including education of physicians and workers about the potential work-relatedness of diseases, may be required.
• Limitations the authors state:
  • The published estimates of cancer due to occupation are specific to the populations studied. Canadian industry is not identical to that in England or the United States, so the proportions would be expected to differ.
  • Cancer registry years (year of diagnosis) did not necessarily correspond to WCB years (year the claim was accepted or rejected).
  • Cancers were not necessarily diagnosed in the province where the exposures occurred, which would cause the largest discrepancies in provinces with strong migration patterns.
  • Labour-force figures overestimate the number of workers insured, and claim rates are likely to be unstable where few claims were reported.
  • Compensation requires that the probability of occupation being a contributing factor be greater than 50%. Population-attributable risk estimates may include workers for whom occupation is not the main risk factor.

Topics

Medical terms in this study, explained in our Lexicon: Attributable Risk, Jurisdiction.

Related studies

• Occupational cancer in Italy — E. Merler, P. Vineis, et al. (1999)
• The current burden of cancer attributable to occupational exposures in Canada — F. Labrèche, J. Kim, et al. (2019)
• A cancer incidence and mortality study of Dow Chemical Canada Inc. manufacturing sites — C. Burns, K. Harrison, et al. (2005)
• Occupational cancer in Germany — I. Brüske-Hohlfeld (1999)
• What is hidden behind urban and semiurban cancer incidence and mortality differences in central Italy? — E. Crocetti, G. Miccinesi, et al. (2002)
• Italian National Register of Occupational Cancers: data system and findings — A. Scarselli, S. Massari, et al. (2010)

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