Arsenic concentrations in prediagnostic toenails and the risk of bladder cancer in a cohort study of male smokers.

At high concentrations, inorganic arsenic can cause bladder cancer in humans. However, it is unclear whether low exposure to inorganic arsenic in drinking water (<100 microg/liter) is related to bladder cancer risk. No study has been known to use biomarkers to assess the relation between individual arsenic exposure and bladder cancer risk. Toenail samples provide an integrated measure of internal arsenic exposure and reflect long-term exposure. The authors examined the relation between toenail arsenic levels and bladder cancer risk among participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, a cohort of Finnish male smokers aged 50-69 years. Data for 280 incident bladder cancer cases, identified between baseline (1985-1988) and April 1999, were available for analysis. One control was matched to each case on the basis of age, toenail collection date, intervention group, and smoking duration. Arsenic levels in toenail samples were determined by using neutron activation analysis. Logistic regression analyses were performed to estimate odds ratios. Arsenic toenail concentrations in this Finnish study were similar to those reported in US studies (range: 0.02-17.5 microg/g). The authors observed no association between inorganic arsenic concentration and bladder cancer risk (odds ratio = 1.13, 95% confidence interval: 0.70, 1.81 for the highest vs. lowest quartile). These findings suggest that low-level arsenic exposure is unlikely to explain a substantial excess risk of bladder cancer.