Transdisciplinary Research Highlights and Challenges Encountered During EPA’s Four Lab Study of Risks Posed by Disinfection By-product Mixtures
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Exposures to drinking water disinfection byproducts (DBPs) pose a significant public health concern given 1) widespread exposures in the U.S. population, and 2) the reproductive and developmental health effects reported previously in some epidemiological studies of DBP mixtures and in toxicological studies of individual DBPs. EPA’s Four Lab Study evaluated DBP whole mixtures for evidence of these two health effects. A team of drinking water treatment engineers, toxicologists, chemists, and risk assessors collaboratively initiated, designed and conducted the study to produce results relevant to DBP health risk assessment. A new procedure was developed for producing chlorinated drinking water DBP concentrates of ~130 times the levels found in finished drinking water for use in toxicology assays. Mixture component proportions were comparable to those reported in treated US drinking waters, including an unidentified fraction of halogenated organic material. Using statistical methods, power calculations were performed for the toxicology studies and the chemical stability of the DBP concentrate was analyzed. Chemical analyses of the DBP concentrates were carried out in tandem with an extensive in vivo and in vitro toxicological testing regimen to investigate associations between assay results and mixture doses, as well as specific DBPs or groups of DBPs. Findings included positive associations observed in in vitro mutagenicity tests in bacteria and a slight but statistically significant delay in puberty onset in vivo in female rats. This series of short talks will provide an overview of this interdisciplinary research effort with an emphasis on transdisciplinary highlights as well as the challenges encountered in EPA's Four Lab Study