Charting a new path to resolve the adverse health effects of DBPs

The disinfection of drinking water was an outstanding public health achievement of the 20th century. Disinfection by-products (DBPs) are the unintended consequence of reactions between disinfectants with organic and halide precursors in the source water. Exposure to DBPs is associated with unfavorable health effects from cancer induction to adverse pregnancy outcomes, yet the forcing agents responsible are largely unknown. Of over 600 DBPs identified, only 11 are regulated by the U.S. EPA and in many studies these are not the most toxic DBPs. Identified DBPs represent less than half of the total organic halogen in drinking water and only ~80 DBPs have been evaluated by systematic quantitative toxicological analyses. Epidemiological studies are hampered by problems with exposure metrics and the suite of DBPs present in drinking water. Although the last decade experienced increased interdisciplinary collaborations amongst chemists, biologists, epidemiologists and engineers, resolving the risks of DBPs follows a dated paradigm. A new integrated approach is required to determine the contaminants in source and drinking waters that increase health risks and to provide the foundation for novel disinfection practices. We suggest the following areas in resolving adverse health effects of DBPs: 1) identification and occurrence of emerging DBPs especially iodinated-DBPs and nitrogenous-DBPs, 2) quantitative, comparative in vitro toxicology of DBPs and DBP classes, 3) a nationwide analysis on the toxicity of drinking waters, 4) determining the impact of DBP precursors and mixture effects on water toxicity, 5) understanding the molecular mechanisms of DBP toxicity, 6) identification of sensitive subpopulations to DBP toxicity, 7) employment of analytical chemistry and toxicity information as an essential part of epidemiological studies, and 8) engineering research on disinfection based on toxic outcomes.