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OCCURRENCE AND TOXICITY OF IODO-ACID AND IODO-THM DBPS IN CHLORAMINATED DRINKING WATER
Citation:
RICHARDSON, S. D., F. G. CRUMLEY, J. J. ELLINGTON, J. J. EVANS, B. C. BLOUNT, L. K. SILVA, F. L. CARDINALI, M. J. PLEWA, AND E. D. WAGNER. OCCURRENCE AND TOXICITY OF IODO-ACID AND IODO-THM DBPS IN CHLORAMINATED DRINKING WATER. Presented at Safe Drinking Water Symposium, Chapel Hill, NC, March 17, 2006.
Impact/Purpose:
(1) Use a toxicity-based approach to prioritize and 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:
As part of a recent Nationwide Disinfection By-Product (DBP) Occurrence Study, iodo-acids were identified for the first time as DBPs in drinking water disinfected with chloramines. The iodo-acids identified included iodoacetic acid, bromoiodoacetic acid, (E)-3-bromo-3-iodo-propenoic acid, (Z)-3-bromo-3-iodo-propenoic acid, and (E)-2-iodo-3-methylbutenedioic acid. They were identified in drinking water samples from a plant using chloramination for disinfection. Gas chromatography (GC) with low and high resolution electron ionization (EI)-mass spectrometry (MS) was used to identify them. These identifications have since been confirmed using authentic chemical standards, both commercial (for iodoacetic acid) and synthesized (for the other four iodo-acids). There is concern about these new iodo-acid DBPs because mammalian cell cytotoxicity and genotoxicity studies have revealed that iodoacetic acid is highly cytotoxic and genotoxic, with a genotoxicity potency 2X higher than bromoacetic acid, the most genotoxic of the regulated haloacetic acids. Also, many drinking water treatment plants in the United States have switched from chlorine to chloramines for treatment. New evidence indicates that the formation of iodinated DBPs will be higher in chloraminated drinking water than in chlorinated drinking water. The goal of this work was to develop an analytical method to quantify these five iodo-acids in drinking water, measure their occurrence in several drinking waters treated with chloramination, determine whether they are maximized in waters treated with chloramines only (compared to chlorine and chlorine-chloramines), and investigate the mammalian cell cytotoxicity and genotoxicity of the four synthesized iodo-acids (beyond iodoacetic acid). In addition, two iodo-trihalomethanes (THMs) - dichloroiodomethane and bromochloroiodomethane - were also measured in this study for comparison purposes to the iodo-acids and to determine whether they are also increased in formation by chloramination.