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EMERGING DISINFECTION BY-PRODUCTS OF TOXICOLOGICAL INTEREST: RESULTS OF A NATIONWIDE OCCURRENCE STUDY
Citation:
Richardson, S D., A D. Thruston Jr., S. W. Krasner, H. S. Weinberg, R. Chinn, M. J. Sclimenti, S. J. Pastor, AND G. D. Onstad. EMERGING DISINFECTION BY-PRODUCTS OF TOXICOLOGICAL INTEREST: RESULTS OF A NATIONWIDE OCCURRENCE STUDY. Presented at Science Forum 2003, Washington, DC, May 5-7, 2003.
Impact/Purpose:
(1) Use toxicity-based approach to identify DBPs that show the greatest toxic response. (2) Comprehensively identify DBPs formed by different disinfectant regimes for the 'Four Lab Study'. (3) Determine the mechanisms of formation for potentially hazardous bromonitromethane DBPs.
Description:
The Safe Drinking Water Act and Amendments requires that EPA address disinfection by-products (DBPs) in drinking water. DBPs are formed when a disinfectant (such as chlorine) reacts with organic matter and/or bromide naturally present in source waters. Drinking water disinfection by-products (DBPs) are of concern because epidemiologic studies indicate that some may be responsible for cancer and reproductive/developmental effects in human populations, and other studies have shown that certain DBPs cause cancer in laboratory animals. A few DBPs are regulated; however, most DBPs have not been tested for adverse health effects due to high costs involved. In order to prioritize new DBPs for health effects testing, we initiated a Nationwide Occurrence Study to quantify ?high priority' DBPs (those predicted by experts to potentially cause an adverse health effect at relatively low doses) to determine how often they occur and at what levels. The fate and transport of these DBPs in the distribution system was also studied, and new DBPs were identified. Scientists from the University of North Carolina and the Metropolitan Water District of Southern California collaborated with NERL scientists on this effort. Drinking waters were chosen across the United States in locations to provide waters with low and high bromide, different pH conditions, and different organic matter levels. Regulated and Information Collection Rule DBPs were also measured for comparison purposes. Analytical methods were developed for quantifying the high priority DBPs in drinking water, and mass spectrometry methods were used to identify new DBPs. Most of the high priority DBPs were found in drinking waters across the U.S.. High priority DBPs identified and quantifiedinclude 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), brominated forms of MX, iodo-trihalomethanes, halomethanes, halonitromethanes, haloacids, haloacetonitriles, haloketones, haloacetates, haloamides, and a few non-halogenated DBPs. Significant results include finding MX at much higher levels than previously believed possible (300-400 ng/L), finding the highest levels of iodo-THMs at a plant using chloramines for disinfection, and finding the highest levels of dihaloaldehydes at a plant using ozonation. In addition, iodo-acids were identified for the first time as DBPs, as well as several new brominated haloacids. Brominated DBPs are important, as toxicology studies suggest that certain brominated DBPs may be of higher health concern than the chlorinated species. This research expands our knowledge on the occurrence of DBPs beyond those that are currently regulated, will help to prioritize future DBP health effects research, and will allow EPA's Office of Water to make improved decisions regarding the safety of drinking water and to ultimately minimize any that are found to be hazardous.