Workplace exposure to asbestos and the risk of kidney cancer in Canadian men

Our plain-English summary of Workplace exposure to asbestos and the risk of kidney cancer in Canadian men, by C.E. Peters, M.É. Parent, S.A. Harris, et al (Canadian Journal of Public Health = Revue Canadienne de Santé Publique, 2018).

The study

• Authors: C.E. Peters, M.É. Parent, S.A. Harris, L. Kachuri, L. Latifovic, L. Bogaert, P.J. Villeneuve, Canadian Cancer Registries Epidemiology Group
• Journal: Canadian Journal of Public Health = Revue Canadienne de Santé Publique
• Published: 2018;109(4):464-472
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: Previous studies considered the role of occupational causes in kidney cancer but were limited by small sample sizes and imprecise exposure assessment. This study examined the relationship between occupational exposure to asbestos and the risk of kidney cancer across a range of jobs in a large, population-based case-control study in Canada.

Methods: Data were from the case-control component of the National Enhanced Cancer Surveillance System, a study conducted between 1994 and 1997 in eight Canadian provinces. Male kidney cancer cases, histologically confirmed, and controls completed questionnaires on socio-demographics, anthropometry, diet, smoking, secondhand smoke exposure, and physical activity. Occupational histories were also collected, including each job held for at least 1 year since the age of 18. Occupational hygienists, blinded to case status, assigned exposure to asbestos, considering intensity, frequency, and probability of exposure (each 3-point scales). Logistic regression was used to estimate the odds of kidney cancer in exposed participants (defined using three metrics) compared to those without asbestos exposure.

Results: There were 712 cases and 2454 controls in these analyses. Ever-exposure to asbestos was associated with 20% increased odds of kidney cancer compared to unexposed workers (OR 1.2, 95% confidence interval 1.0-1.4 when including possibly exposed workers). A small increase in risk was observed with cumulative exposure, while increasing intensity of exposure was related to increased odds of kidney cancer.

Conclusions: This study found some evidence for an association between occupational exposure to asbestos and kidney cancer. Higher intensity of exposure to asbestos had the strongest relationship with kidney cancer risk.

In plain English

This population-based case-control study, using data collected from 1994 to 1997 in eight Canadian provinces, examined whether workplace asbestos exposure was associated with kidney cancer in men. It included 712 men with histologically confirmed kidney cancer and 2454 cancer-free controls. An occupational hygienist blinded to case status rated each job's asbestos exposure and how confident that rating was. Fiber types were not distinguished. Including men whose exposure was rated only possible, ever-exposed men had 20% higher adjusted odds of kidney cancer than unexposed men (odds ratio 1.2, 95% confidence interval 1.0 to 1.4). Counting only probable or definite exposure, the odds ratio was 1.3 (1.0 to 1.6). For men whose highest exposure intensity was medium or high, the odds ratios were 1.4 (0.7 to 2.7; 16 cases) and 1.6 (0.8 to 3.4; 15 cases) under the same two definitions. Cumulative exposure results did not rise steadily. The authors concluded there was some evidence of a relationship, more pronounced at higher intensity. They noted possible participation bias, no direct exposure measurements, a single expert rater, and no trichloroethylene data.

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: Population-based case-control study (the case-control part of the National Enhanced Cancer Surveillance System, NECSS), analysed with unconditional logistic regression
• Who was studied: Men in eight Canadian provinces, 1994 to 1997: 712 histologically confirmed kidney cancer cases (83% renal cell carcinoma) and 2454 population-based cancer-free controls with complete work histories. Response rates were 73% for male cases and 63% for male controls.
• Exposure: Occupational asbestos exposure (fiber type not specified). For each job held at least 1 year since age 18, an occupational hygienist blinded to case status rated intensity (low, medium, high), frequency (under 5%, 5 to 30%, over 30% of the work week) and confidence (possible, probable, definite). The most common exposed jobs were construction, mechanics/repair/fabrication, stationary engine and utilities, water transportation, and firefighters.
• Main results:
  • Ever exposed versus never exposed, including possibly exposed men (267 cases, 783 controls exposed): fully adjusted odds ratio 1.2 (95% CI 1.0 to 1.4); minimally adjusted 1.3 (1.1 to 1.6).
  • Restricted to probable or definite exposure (99 cases, 267 controls exposed), the fully adjusted odds ratio for ever exposure was 1.3 (1.0 to 1.6). The authors described this as consistent with the analysis that included possible exposure.
  • Highest attained intensity, medium/high versus unexposed, fully adjusted. Including possible exposure (16 cases, 33 controls), the odds ratio was 1.4 (0.7 to 2.7), with p for trend 0.027. Restricted to probable/definite exposure (15 cases, 26 controls), the odds ratio was 1.6 (0.8 to 3.4), with p for trend 0.07. The authors said the significant trend tests were likely influenced by including the reference group.
  • Only 2 or 3 men had high-intensity exposure, so the high category was combined with medium.
  • Cumulative exposure, fully adjusted, including possible exposure: low 1.3 (1.0 to 1.8), medium 1.1 (0.8 to 1.5), high 1.2 (0.9 to 1.6), with p for trend 0.066. The odds did not increase steadily with cumulative exposure.
  • Restricted to renal cell carcinoma and excluding possibly exposed workers, men who ever had moderate or high exposure had an odds ratio of 1.5 (95% CI 0.8 to 3.2). Restricting to men over 40 gave an odds ratio of 1.3 (0.6 to 2.5) for highest attained exposure, compared with 1.4 at all ages.
• The authors' conclusion: The authors concluded that they found some evidence of a relationship between occupational asbestos exposure and kidney cancer risk in Canadian men, more pronounced for workers exposed at higher intensity.
• Limitations the authors state:
  • Possible recall bias in the confounding variables because data were collected retrospectively.
  • Participation rates (73% cases, 63% controls) leave potential for participation bias.
  • No information on trichloroethylene exposure, an established kidney cancer risk factor.
  • Exposure was assessed by a single expert.
  • Asbestos exposure was not directly measured.
  • There was no consistent exposure-response relationship for cumulative exposure, which the authors suggested may reflect non-differential misclassification of exposure.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Case-Control Study, Asbestos Exposure, confidence interval, Cumulative Exposure.

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• Heavy metals, welding fumes, and other occupational exposures, and the risk of kidney cancer: A population-based nested case-control study in three Nordic countries — I.M. Michalek, J.I. Martinsen, et al. (2019)
• Occupational exposure to asbestos and risk of kidney cancer: an updated meta-analysis — C. Zunarelli, A. Godono, et al. (2021)
• Kidney cancer and hydrocarbon exposures among petroleum refinery workers — C. Poole, N.A. Dreyer, et al. (1993)
• Occupational exposure to asbestos and lung cancer in men: evidence from a population-based case-control study in eight Canadian provinces — P.J. Villeneuve, M.É. Parent, et al. (2012)

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