Drinking water mutagenicity and urinary tract cancers: a population-based case-control study in Finland

The detection of mutagenic and carcinogenic chlorination by-products in chlorinated drinking water has raised concern in many countries over the potential health effects of long-term exposure to these products. The relation between estimated exposure to historical drinking water mutagenicity and cancer was studied in Finland by using a population-based case-control study comprising 732 bladder cancer cases, 703 kidney cancer cases, and 914 controls. The cases were obtained from the nationwide Finnish Cancer Registry for the years 1991-1992. The controls, frequency matched by age and sex, were randomly selected from the national population registry. Information on past drinking water sources and confounding factors was acquired through a questionnaire. Historical exposure to drinking water mutagenicity was estimated by using information on past residence, past water source, and historical data on water quality and treatment. Odds ratios were calculated for an increase of 3,000 net revertants per liter (net rev/liter) in average exposure from 1950 to 1987, adjusting for age, sex, socioeconomic status, and smoking in logistic regression models. A small, statistically significant, exposure-related excess risk was found for kidney cancer for men (odds ratio = 1.49, 95 percent confidence interval (CI) 1.05-2.13) for 3,000 net rev/liter exposure level. For women, the association remained nonsignificant, with a lower odds ratio of 1.08 (95% CI 0.69-1.68). For bladder cancer, the odds ratio for both men and women was 1.22 (95% CI 0.92-1.62) for 3,000 net rev/liter exposure. However, a higher odds ratio of 2.59 (95% CI 1.13-5.94) for 3,000 net rev/liter exposure was observed for male nonsmokers.