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Application of Toxicological and Health Risk Assessment Approaches to Investigate Chemical Constituents in Drinking Water
Citation:
SIMMONS, J. E. Application of Toxicological and Health Risk Assessment Approaches to Investigate Chemical Constituents in Drinking Water. Presented at 1st China-US Workshop on Environmental Science and Technology Cooperation, Beijing, CHINA, April 01 - 03, 2008.
Impact/Purpose:
ORD’s Integrated DBP Mixtures Research Project was developed to better understand potential adverse health effects of DBP exposure that cannot be determined by investigation of individual DBPs or defined mixtures of DBPs. The project involved using novel methods for preparation of water concentrates, experimental animal water delivery systems, and conducting a multi-generational rat reproductive/developmental bioassay. Improved understanding of the potential human health risks from exposure to the mixtures of DBPs formed during disinfection of water requires integration of knowledge gained from the toxicological evaluation of individual DBPs, defined DBPs mixtures and highly-complex environmentally realistic mixtures of DBPs.
Description:
Chemical disinfection of water has been practiced since the beginning of the 20th century and has resulted in significant gains in public health protection due to decreased exposure to microorganisms responsible for water-borne diseases. While disinfection chemicals, such as chlorine, are effective for inactivating pathogens, they can also react with constituents in water and produce a suite of chemicals that are referred to as disinfection byproducts (DBPs). The rate, extent, and complexity of DBP formation depends on source water characteristics, disinfection conditions, and the characteristics of the water distribution system. Research on DBPs has evolved over the past 30 years and, although over 600 individual DBPs have been identified, questions remain on how to predict the suite of DBPs present in disinfected drinking water and potential health concerns. Data collected on the health effects of DBPs can be classified into studies of: individual DBPs; defined mixtures containing a small number of DBPs (2 to 10 DBPs); or, complex DBP mixtures, including epidemiological studies and toxicological evaluations. Research on defined DBP mixtures pointed to additivity as the predominant toxicological response observed at environmentally relevant dose regions and mixing ratios. However, the relationship between dose and response is dependent on the relative proportions of DBPs present in the mixture.