Citation:

Sey, Y., C. Postigo, M. Armstrong, D. DeMarini, T. Mcdonald, H. Liberatore, K. Lamman, S. Kimura, A. Cuthbertson, S. Richardson, N. Ackerson, S. Duirk, S. Warren, AND J. Simmons. THE INFLUENCE OF IODINATED CONTRAST MEDIA ON DISINFECTION BYPRODUCT (DBP) SPECIATION AND MUTAGENICITY. Society of Toxicology Annual Meeting, Baltimore, Maryland, March 10 - 14, 2019.

Impact/Purpose:

Interest in the presence of pharmaceuticals and contaminants of anthropogenic origin in water is increasing. Iodinated x-ray contrast media are pharmaceutical agents likely to be present in wastewater effluents, thus entering surface waters that serve as source waters for drinking water treatment plants. The study described in this abstract represents the most comprehensive chemical analysis effort to date to understand the impact of chlorination of source water containing iodinated x-ray contrast media. In particular, analysis of regulated disinfection byproducts and those disinfection byproducts that are more routinely measured along with iodinated disinfection byproducts, provides a useful context for the concentrations of iodinated compounds observed. Integration of chemical and toxicological analysis was accomplished by assessment of mutagenicity of the chlorinated extracts in Salmonella with and without exogenous metabolic activation. Results indicated that some of the mutagenicity of the samples was due to brominated disinfection byproducts. Although chlorination of source water containing any of the four ICMs evaluated (iopamidol, iopromide, iohexol, and diatrizoate) resulted in increased concentrations of I-DBPs, there was no increase in the mutagenicity of the waters.

Description:

Chlorine remains the most frequently used drinking water disinfectant in the U.S. DBPs (more than 700 identified) are formed when oxidizing disinfectants react with natural organic matter and bromide/iodide in water. Some DBPs are known mutagens, genotoxicants, cytotoxicants, reproductive toxicants, and/or carcinogens. Increased attention is being placed on the role of anthropogenic water contaminants in DBP formation. Iodinated contrast media (ICM) are used in medical imaging of soft tissues and enter surface waters due to poor removal during wastewater treatment. ICM have been identified as iodine precursors that may enhance the formation of iodinated DBPs (I-DBPs). In the current study, source water containing one of the four ICM, iopamidol (IPAM), iohexol, iopromide, or diatrizoate, which are the ones detected most frequently in water, was chlorinated; non-chlorinated ICM-containing water samples served as controls. We quantified 21 regulated and non-regulated DBPs, 11 target I-DBPs, and performed a non-targeted, comprehensive, broad-screen identification of I-DBP formation. Mutagenicity of XAD-resin extracts of non-chlorinated and chlorinated ICM-containing water was examined in Salmonella strains with and without metabolic activation. ICM alone, i.e., without chlorination, did not result in DBP formation. However, the presence of IPAM increased chlorine demand and enhanced formation of bromoacetic acid, trichloroacetic acid, bromochloroacetonitrile, dichloroacetonitrile, and trichloroacetaldehyde. IPAM also enhanced the formation of I-DBPs, notably dichloroiodomethane, chloroiodomethane, iodoacetaldehyde,iodoacetic acid, and chloroiodoacetic acid. Non-targeted, comprehensive, broad-screen analysis identified novel I-DBPs, including 1 new iodomethane, 3 new iodoacids, and 2 new iodoacetronitriles. Mutagenicity of chlorinated source water was not increased by addition of any of the 4 tested ICM, regardless of metabolic activation status. In summary, DBP concentrations, including I-DBPs, were increased in extracts of chlorinated IPAM-containing source water, but Salmonella mutagenicity was not. [This abstract does not reflect EPA policy.]

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