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THE OCCURRENCE OF DISINFECTION BY-PRODUCTS OF HEALTH CONCERN IN DRINKING WATER: RESULTS OF A NATIONWIDE DBP OCCURRENCE STUDY
Citation:
Weinberg, H. S., S. W. Krasner, S D. Richardson, AND A D. Thruston Jr. THE OCCURRENCE OF DISINFECTION BY-PRODUCTS OF HEALTH CONCERN IN DRINKING WATER: RESULTS OF A NATIONWIDE DBP OCCURRENCE STUDY. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-02/068 (NTIS PB2003-106823), 2002.
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 motivation for this Nationwide Disinfection By-product (DBP) Occurrence Study was two-fold: First, more than 500 DBPs have been reported in the literature, yet there is almost no quantitative occurrence information for most. As a result, there is significant uncertainty over the identity and levels of DBPs that people are exposed to in their drinking water. Second, only a limited number of DBPs have been studied for adverse health effects. So, it is not known whether other DBPs (besides the few that are currently regulated) pose a risk to human health. To determine whether other DBPs pose an adverse health risk, more comprehensive quantitative occurrence and toxicity data are needed.
Because health effects studies are very expensive, it is not possible to test all DBPs that have been reported. It is also not feasible to measure >500 DBPs in waters across the United States. Thus, results of a DBP prioritization effort by scientists at the U.S. Environmental Protection Agency (USEPA) Office of Water and the USEPA Office of Prevention, Pesticides, and Toxic Substances were used to focus this study on those DBPs that were the most toxicologically significant. These EPA experts applied an in-depth mechanism-based structural activity relationship analysis to the more than 500 DBPs reported in the literature, supplemented by an extensive literature search for genotoxicity and other data, and ranked the carcinogenic potential of these DBPs. Approximately 50 DBPs that received the highest ranking for potential toxicity and that were not included in the USEPA's Information Collection Rule (ICR) were selected for this occurrence study. These DBPs, denoted as 'high priority' DBPs in this report, included such compounds as MX [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone], brominated forms of MX (BMXs), halonitromethanes, iodo-trihalomethanes, and many brominated species of halomethanes, haloacetonitriles, haloketones, and haloamides.