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Genotoxicity of Disinfection By-products: Comparison to Carcinogenicity
Citation:
DEMARINI, D. M. Genotoxicity of Disinfection By-products: Comparison to Carcinogenicity. Chapter 2, Nriagu, Jerome (ed.), Encyclopedia of Environmental Health. Elsevier Online, New York, NY, 2:920-926, (2011). https://doi.org/10.1016/B978-0-444-52272-6.00104-5
Impact/Purpose:
A comprehensive review of the DBP and drinking water literature had never been done, and after 30 years, it was time to see what has been learned and what still needed to be done in this important area of environmental science. The lack of such a review has prevented a thoughtful assessment of the current state of knowledge in DBP research and has hindered the development of a comprehensive plan for future research based on what has been learned already. Thus, the review was undertaken to provide the necessary information and guidance for prioritizing DBP and drinking water research. The present chapter summarizes briefly the main findings of this 2007 review for the educated layman.
Description:
Disinfection by-products (DBPs) can be formed when water is disinfected by various agents such as chlorine, ozone, or chloramines. Among the >600 DBPs identified in drinking water, 11 are regulated by the U.S. Environmental Protection Agency, and another ~70 DBPs that occur at similar levels are unregulated. The regulated DBPs are bromodichloro- and chlorodibromomethane; bromoform; chloroform; chloro-, bromo-, dibromo-, dichloro-, and trichloroacetic acid; bromate, and chlorite. Eight of the regulated DBPs are generally genotoxic; however, significant data gaps exist for chromosomal mutation for the haloacetic acids other than dichloroacetic acid. Two of the regulated DBPs, chloroform and trichloroacetic acid, are generally not genotoxic, and one, chlorite, has never been tested for genotoxicity. Nine of the 11 regulated DBPs show evidence of carcinogenicity in rodents, with chloroacetic acid being negative and bromoacetic acid not ever tested. Among the ~70 unregulated DBPs that generally occur at levels similar to those of the regulated DBPs, approximately half are genotoxic, and the remainder have generally not been tested for genotoxicity. Among the 10 that have been tested for rodent carcinogenicity, all are carcinogenic. Emerging data suggest that dermal/inhalation exposure to the brominated trihalomethanes may be associated with the increased risk for bladder cancer found among consumers of chlorinated drinking water. One regulated DBP (chloroform) and two unregulated ones (acetaldehyde and formaldehyde) have been tested in rodents via inhalation and are carcinogenic. No DBP has been tested for carcinogenicity via dermal exposure. None of the toxicological testing of individual DBPs reflects the complexity of the complex mixture of >600 DBPs to which many people are exposed via a variety of routes. The data gaps and emerging issues described here provide guidance for further drinking water and public health research.
