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ORD'S FOUR LAB STUDY: TOXICOLOGICAL AND CHEMICAL EVALUATION OF COMPLEX MIXTURES OF DRINKING WATER DISINFECTION BY-PRODUCTS
Citation:
Teuschler, L K., J E. Simmons, E. Hunter, L D. Claxton, M. Narotsky, R. Pegram, E Rice, S. D. Richardson, R J. Miltner*, T F. Speth*, AND K M. Schenck*. ORD'S FOUR LAB STUDY: TOXICOLOGICAL AND CHEMICAL EVALUATION OF COMPLEX MIXTURES OF DRINKING WATER DISINFECTION BY-PRODUCTS. Presented at WSWRD Peer Review, Cincinnati, OH, September 27 - 29, 2004.
Impact/Purpose:
To inform the public.
Description:
Disinfectants used in the production of drinking water react with naturally occurring organic and inorganic material in the source water to produce disinfection by-products (DBPs). Humans are exposed daily to a complex mixture of DBPs via oral, dermal, and inhalation routes. To date, hundreds of chemically distinct DBPs have been identified; yet, ~50% of the DBP mass is composed of unidentified chemicals. Epidemiological studies suggest cancer and reproductive/developmental effects are associated with consumption of chlorinated drinking water. However, current single-chemical toxicology studies fail to corroborate epidemiological findings. A critical data gap is toxicological and chemical evaluation of the complex DBP mixture, targeting the endpoints identified in epidemiological studies. To address this gap, EPA's Office of Research and Development launched a joint research project across its four laboratories. Its design is to:1) produce concentrates of drinking water samples formed using different disinfectants for the same source water; 2) perform analytical chemistry to characterize the known and unknown DBPs in the mixture and to test the mixture's stability; 3) perform in vivo and in vitro toxicological testing; 4) use statistical design and analysis to provide data useful in risk assessment, attributing toxicity to the known and unknown fractions of the complex mixture. The work will be available to the Office of Water to assist them in decisions on complex mixtures. Progress to date includes a draft research proposal and trial runs to determine feasibility of a full study. Trial run results include development of concentration methods and procedures to "spike back" lost volatile DBPs, evidence of chemical integrity of samples over time, palatability of water to test animals, and initial results from limited toxicological testing. Next step is to conduct the full study with in vitro tests, a multi-generational reproductive/developmental study and other in vivo studies to gather extensive toxicological data on relevant health endpoints and to more fully characterize the chemical composition of the complex DBP mixture.