Background: Disinfection by-products in drinking water are chemical contaminants that have been associated with cancer and other adverse effects. Exposure occurs from consumption of tap water, inhalation and dermal absorption. Methods: We determined the relationship between socioeconomic status and exposure to disinfection by-products in 1271 controls from a multicentric bladder cancer case-control study in Spain. Information on lifetime drinking water sources, swimming pool attendance, showering-bathing practices, and socioeconomic status (education, income) was collected through personal interviews. Results: The most highly educated subjects consumed less tap water (57%) and more bottled water (33%) than illiterate subjects (69% and 17% respectively, p-value = 0.003). These differences became wider in recent time periods. The time spent bathing or showering was positively correlated with attained educational level (p < 0.001). Swimming pool attendance was more frequent among highly educated subjects compared to the illiterate (odds ratio = 3.4; 95% confidence interval 1.6-7.3)./n/nConclusions: The most highly educated subjects were less exposed to chlorination by-products through ingestion but more exposed through dermal contact and inhalation in pools and showers/baths. Health risk perceptions and economic capacity may affect patterns of water consumption that can result in differences in exposure to water contaminants.

This work was supported by the Intramural Program of the National Institutes of Health, National Cancer Institute (NCI), Division of Cancer Epidemiology and Genetics, NCI-Westat contract no. N02-CP-11015, FIS/Spain 00/0745, G03/174, PI061614, CA34627, and Red Temática de Investigación Cooperativa en Cáncer (RTICC). Cristina M Villanueva has a contract funded by the Instituto de Salud Carlos III, Spanish Ministry of Health and Consumption (CP06/00341).