Occurrence and Toxicity of Iodinated Disinfection By-Products in Drinking Water

摘要

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. There is concern because toxicity 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. For this research, a gas chromatography (GC)/negative chemical ionization mass spectrometry (MS) method was developed to measure the iodo-acids in drinking waters across the U.S., and two iodinated trihalomethanes (THMs) (dichloroiodomethane and bromochloroiodomethane) were measured using a GC/high resolution electron ionization-MS method with isotope dilution. Iodoacetic acid, bromoiodoacetic acid, and (E)-2-iodo-3-methylbutenedioic acid were found in most of the plants sampled, at sub-ppb to low-ppb levels; the two iodo-THMs were found at all plants sampled, at low ppb or sub-ppb levels (with a high of 10.2 ppb for bromochloroiodomethane). New toxicity work is underway for the other iodo-acids (beyond iodoacetic acid) and for the two iodo-THMs; these new toxicity data will be presented, along with measurements of iodide in the source waters.