National Toxicology Program

It is estimated that more than 200 million Americans use municipally treated drinking water, so the availability of safe drinking water is of enormous public health significance. Although chlorination is considered one of the major public health advances of the twentieth century, chemical disinfection by-products (DBPs) of chlorination or other disinfection processes may cause health problems such as cancer. In addition, there are agents found naturally in water or are present by contamination of public water systems that may pose a threat to public health. The U.S. Environmental Protection Agency (EPA) has responsibility to set water standards for DBPs. To provide scientific data for setting sound water quality standards, the NTP is collaborating with the EPA on a research program which includes a systematic, mechanism-based, toxicological evaluation of DBPs focusing on reproductive toxicity, immunotoxicity, neurotoxicity, and carcinogenicity. Selection of DBPs for study is based on their presence in drinking water, occurrence with different disinfection processes, chemical structures, and representation of several DPB classes: trihalomethanes, haloacetic acids, and haloacetonitriles.