Impact/Purpose:

The purpose of these studies is to evaluate the potential immunotoxic effects of selected disinfection by-products (DBPs) in laboratory animals. If products associated with current disinfection processes do decrease immune function, the risk of immunosuppression and increased susceptibility to infection must be balanced against the risks posed by increased microbial load, if less effective disinfection methods are mandated. These studies will provide qualitative and quantitative data that will be considered in the process of setting MCLGs/MCLs for DBPs.

Description:

Few DBPs have been evaluated for effects on the immune system, but certain studies suggest that immunosuppression may follow exposure to DBPs. Suppressed immune function is associated with increasesd susceptibility to infectious disease and certain types of cancer in humans and laboratory animals. Screening studies for immunotoxicity were therefore included as part of the projects identified for funding from the SDWA $10 million authorization for health effects research on drinking water contaminants. A collaborative project between EPA and the National Toxicology Program (NTP) will initially examine six DBPs commonly found in finished drinking water. The chemicals were chosen from different classes of by-products; they are dibromoacetic acid, dichloroacetic acid, bromate, chloroform, chlorite and chloramine. Following chemical stability studies, experimental doses will be chosen from published studies, when feasible. Mice will be exposed to the selected chemicals in drinking water for 28 days. Immune function will be assessed using the NTP immunotoxicity testing tier to evaluate specific and nonspecific immune functions. A maximum of two chemicals will be subjected to a full protocol immunotoxicity study, including host resistance, if signs of immunotoxicity are found.

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