You are here:
DISINFECTION BY-PRODUCTS OF HEALTH CONCERN IN DRINKING WATER: RESULTS OF A U.S. 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. DISINFECTION BY-PRODUCTS OF HEALTH CONCERN IN DRINKING WATER: RESULTS OF A U.S. NATIONWIDE OCCURRENCE STUDY. Presented at International Mass Spectrometry Conference, Edinburgh, Scotland, August 31 - September 5, 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 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 (NOM and bromide are DBP precursors; pH impacts the formation and stability of many DBPs). For comparison purposes, regulated and Information Collection Rule DBPs were quantified along with the high priority DBPs. Drinking water samples were collected at the treatment plants and in the distribution systems. 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. In previous limited studies, MX was found at levels up to 60 parts-per-trillion (ng/L); however, in this study, MX reached levels of 300-400 ng/L at certain locations. Iodinated DBPs, including iodo-trihalomethanes, were also detected in many drinking waters sampled, even those with relatively low bromide (and probably low iodide) levels. Although chloramines are used to reduce trihalomethane formation, previous bench-scale studies indicated that ammonia addition before chlorination (to form chloramines) could favor the formation of iodinated DBPs. In this full-scale study, iodo-trihalomethanes were highest at a plant that used chloramines only for disinfection. Also while ozone and chloramines generally control the formation of trihalomethanes and other trihalo species, some dihalo species (such as dihaloaldehydes) were higher at plants using ozonation and/or 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 in the Southwest 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.