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DISINFECTION BY-PRODUCTS OF EMERGING CONCERN: RESULTS OF A U.S. NATIONWIDE OCCURRENCE STUDY
Citation:
Richardson, S D., A D. Thruston Jr., S. W. Krasner, R. Chinn, M. J. Sclimenti, S. Pastor, H. S. Weinberg, AND G. D. Onstad. DISINFECTION BY-PRODUCTS OF EMERGING CONCERN: RESULTS OF A U.S. NATIONWIDE OCCURRENCE STUDY. Presented at International Workshop Pool Water Chemistry, Drinking Water Disinfection By-Products and Health, Karlsruhe, Germany, September 22-24, 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:
Drinking water disinfection by-products (DBPs) are of concern because some epidemiologic studies have shown that some DBPs are associated with cancer or adverse reproductive/developmental effects in human populations and other studies have shown that certain DBPs cause similar health effects in laboratory animals. As a result, the U.S. Environmental Protection Agency (EPA) has regulated several DBPs; however, most DBPs have not been tested for adverse health effects due to the high costs involved. In order to prioritize new DBPs for health effects testing, we initiated a U.S. Nationwide Occurrence Study to quantify ?high priority' DBPs (those predicted by toxicology experts to possibly have an adverse health effect) 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.
Drinking water samples were collected across the United States from 12 plants that use chlorine, ozone, chlorine dioxide, and/or chloramines for disinfection. Locations were chosen to provide waters that contain low and high bromide levels, different pH conditions, and different natural organic matter (NOM) levels. For comparison purposes, regulated and Information Collection Rule DBPs were quantified along with the high priority DBPs. Quantitation methods developed involved various extraction, derivatization, and detection methods (including solid-phase extraction, liquid-liquid extraction, solid-phase microextraction, and purge-and-trap with GC/electron capture detection or GC/MS). For identifying new DBPs, GC with low and high resolution electron ionization-MS and chemical ionization-MS were used.
Many of the high priority DBPs were found in drinking waters across the United States. High priority DBPs identified and quantified include 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and brominated forms of MX (the so-called BMXs), iodo-trihalomethanes, other halomethanes, halonitromethanes, haloacids, haloacetaldehydes, haloacetonitriles, haloketones, haloacetates, haloamides, and a few non-halogenated DBPs. Important findings include levels of MX being higher (300-400 ng/L at certain locations) than in previous limited studies. In addition, while the use of alternative disinfectants minimized the formation of the four regulated trihalomethanes, certain DBPs were formed at significant concentrations. For example, iodo-trihalomethanes were highest at a plant that used chloramines only for disinfection; dihaloaldehydes were higher at plants using ozonation and/or chloramination; bromo-trihalonitromethanes were highest at a plant using pre-ozonation (followed by chloramination); and MX and BMX compounds were highest at a plant using chlorine dioxide (followed by chlorination-chloramination). Another important finding was the discovery of iodo-acids. Iodo-acids have never been reported previously for any disinfectant. Five iodo-acids (iodoacetic acid, iodobromoacetic acid, iodobromopropenoic acid (2 isomers), and 2-iodo-3-methylbutenedioic acid) were identified in drinking water from a plant that used chloramine disinfection for high-bromide source waters. Many new brominated haloacids were also identified in drinking waters from several states. Brominated DBPs are important, as current toxicology (and some recent epidemiology) studies suggest that certain brominated DBPs may be of higher health concern than the chlorinated species. Also, preliminary studies with iodoacetic acid show that it is more genotoxic to mammalian cells than brominated DBPs (including bromoacetic acid) and is a developmental toxin in mouse embryos.