Approaches for Modeling Exposure to Specific Trihalomethanes and Bladder Cancer Risk

Lifetime exposure to trihalomethanes (THM) has been associated with increased risk of bladder cancer. THMs are formed as by-products when chlorine is used to disinfect water for drinking. They are part of a group of chemicals known as disinfection by-products (DBPs) and THMs represent the chemical class of DBPs occurring at highest concentrations. They result from the reaction of chlorine and/or bromine with organic matter present in the water during treatment.

A research at the Centre for Research in Environmental Epidemiology (CREAL) lead by Dr. Lucas Salas, in the framework of a project coordinated by Dr. Cristina M. Villanueva, recently published in the American Journal of  Epidemiology, had explored methods to analyze bladder cancer risk associated with the 4 main THM (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) as surrogates of DBP mixtures in a case control study conducted in Spain (1998–2001).

Lifetime average concentrations of THMs were calculated in the households of incident bladder cancer cases and matched hospital-based controls. THM concentrations, composition, and correlations between components varied among areas. The estimation of bladder cancer risk associated with total THM showed increased risks with increasing exposure. Analyses for separate THMs provided unstable bladder cancer risk estimates and inconsistent exposure-response relationships. “The main conclusion of our study is that total THMs (μg/L) provided a proxy measure of DBPs that yielded the strongest exposure-response relationship with bladder cancer risk”, said Salas.

Reference

Salas LA, Cantor KP, Tardón A, Serra C, Carrato A, García-Closas R, Rothman N, Malats N, Silverman D, Kogevinas M, Villanueva CM. Biological and Statistical Approaches for Modeling Exposure to Specific Trihalomethanes and Bladder Cancer Risk. Am J Epidemiol 2013 (in Press).