Research and Guidance on Drinking Water Contaminant Mixtures

Accurate assessment of potential human health risk(s) from multiple-route exposures to multiple chemicals in drinking water is needed because of widespread daily exposure to this complex mixture. Hundreds of chemicals have been identified in drinking water with the mix of chemicals varying with geographic location, source waters, disinfection scenarios and surrounding land uses and industries. Mixtures in drinking water can consist of many chemical classes, e.g., pesticides, pharmaceuticals, metals, polychlorinated biphenyls, and disinfection by-products (DBPs). In some cases, positive data from epidemiological or toxicological studies raise concerns for human health. Depending on the chemical properties of these contaminants, they may be present in liquid, vapor, or aerosol form(s) and can enter the body via ingestion, respiration, or dermal penetration. DBPs are a particularly important class of chemicals that are formed as a consequence of chemical reactions among the disinfectant used to treat the water, naturally occurring organic matter and bromide. Listed below are a number of reports and journal publications that address human health risk assessment and toxicology of drinking water contaminant mixtures.

Research on Drinking Water Disinfection By-Products (DBPs)

• ENGLEHARDT, J. AND J. C. SWARTOUT. Development and Evaluation of Novel Dose-Response Models for Use in Microbial Risk Assessment. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/033.
• U.S. EPA. 2006. Drinking Water Exposures and Internal Doses of Trihalomethanes in Humans. Cincinnati, Oh. NCEA-C-1691.
• U.S. EPA. 2003. the Feasibility of Performing Cumulative Risk Assessments for Mixtures of Disinfection By-Products in Drinking Water. Cincinnati, Oh. EPA/600/R-03/051.
• U.S. EPA. 2000. Conducting a Risk Assessment of Mixtures of Disinfection By-Products (DBPs) for Drinking Water Treatment Systems. Cincinnati, Oh. EPA/600/R-03/040.
• U.S. EPA. 1999. Research Report on the Risk Assessment of Mixtures of Disinfection By-Products (DBPs) in Drinking Water. Cincinnati, Ohio. EPA/600/R-03/039.
• Development of a Research Strategy for Integrated Technology-Based Toxicological and Chemical Evaluation of Complex Mixtures of Drinking Water Disinfection Byproducts
• Epidemiological Work on DBP Exposures

Other Drinking Water Contaminants and Single Chemical Information

• Developing Relative Potency Factors for Pesticide Mixtures: Biostatistical Analyses of Joint Dose-Response
• ATSDR Toxicological Interaction Profiles
• IRIS
• NIH National Library of Medicine Toxnet
• OWs List of Drinking Water Contaminants & MCLs
• OPPs Research and Guidance on Aggregate Exposures to Pesticide Mixtures

Guidance on Health Risk Assessment of Chemical Mixtures

• EPA Guidelines for Chemical Mixtures Risk Assessment 2000 Supplementary Guidance and 1986 Guidelines
• Technical Support Document on Risk Assessment of Chemical Mixtures
• ATSDR Guidance on Chemical Mixture Health Risk Assessments

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