Associations of cancer mortality with halomethanes in drinking water.

Associations between site- and sex-specific county cancer mortality rates and levels of trihalomethanes (THM's) in drinking water were examined after adjustment of rates for the influence of multiple socioeconomic, industrial, and demographic factors. U.S. counties with sampled supplies were grouped by percent of the county population receiving water from the supply, as well as by region of the country. For two sites (bladder and lung), county rates were also adjusted for the activity level in specific high-risk industries. Positive correlations with THM levels were observed for several cancers, including bladder and brain cancers in both sexes, and non-Hodgkin's lymphoma and kidney cancer in males. Stomach cancer in females showed a negative association. Bladder cancer mortality rates showed the strongest and most consistent association with a THM exposure index, after control for differences in social class, ethnic group, urban versus rural residence, region of the United States, and industrialization of the county. These ecologic associations suggested that further evaluation in analytic investigations is warranted.