Kidney cancer and occupational exposure to asbestos: a meta-analysis of occupational cohort studies

Objective: To study the risk of kidney cancer following asbestos exposure. Methods: We carried out a meta-analysis of the results of cohort studies of workers predominantly exposed to asbestos. We contacted the authors of 70 cohort studies; published results were available from the reports of 10 cohorts; we obtained the relevant information for an additional 27 cohorts. Results: The studies included in the analysis comprised a total of 169 kidney cancer deaths and 69 incident cases. The overall pooled standardized mortality ratio (SMR) of kidney cancer was 1.1, with a 95% confidence interval (95% CI) of 0.9-1.3. The pooled SMR was higher for workers with undefined asbestos exposure (SMR 1.2, 95% CI 0.9-1.6) than for workers with either predominant chrysotile (SMR 0.9, 95% CI 0.7-1.3) or some amphibole (SMR 0.96, 95% CI 0.6-1.5) exposure. Studies with published results had higher SMRs than studies for which information was obtained from the authors. Studies with high asbestos exposure and an elevated SMR of lung cancer tended to show an increased risk of kidney cancer. Conclusions: It is unlikely that asbestos exposure is responsible for an important increase in kidney cancer risk; however, high asbestos exposure might entail a small increase in risk.