Impact/Purpose:

Research in this area focuses on developing scientifically sound data and approaches to assess and manage risks to human health posed by exposure to regulated waterborne pathogens and chemicals, including those addressed by the Arsenic, Microbial/Disinfection By-Products, and Six-Year Review Rules.

Description:

The most common classes of the disinfection by-products (DBPs) encountered in chlorinated systems are regulated with average annual limits for total trihalomethanes (80 μg/liter) and a sum of five of the haloacetic acids (60 μg/liter). Questions persist regarding noncancer health effects of DBPs, including adult and developmental neurotoxicity. In particular, there is concern that new generations of DBPs, such as brominated and iodinated species, can have greater potency for certain health outcomes than their chlorinated analogues. Earlier work in NTD had characterized neurobehavioral toxicity produced by dichloroacetic acid (DCA) in rats. To test the hypothesis that other haloacetic acids produced similar effects, NTD conducted a 6-mo study of DBA, second in ambient level to DCA in drinking water. Behavioral evaluations were conducted periodically during exposure, and pathological evaluations of the nervous system were conducted at the termination of exposure. DBA produced neuromuscular toxicity and sensorimotor depression. Neuropathological findings included degeneration of spinal cord nerve fibers and cellular vacuolization in spinal cord gray matter. The lowest dose tested produced significant neurobehavioral changes. Both DBA and DCA produced neuromuscular toxicity, although DBA alone also affected sensory responsiveness. The pattern of neuropathologic alterations observed in spinal cord was similar to that previously reported for DCA.

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