Citation:

MedlockKakaley, E., N. Evans, J. Conley, E. Gray, P. Bradley, K. Smalling, AND K. Romanok. Effects-based bioassay screening approaches applied to residential tapwater to inform consumer point-of-use decisions. Society of Environmental Toxicology and Chemistry, Louisville, KY, November 12 - 16, 2023.

Impact/Purpose:

The abstract summarizes several case studies, conducted in collboration with the US Geological Survey, that were designed to address a critical lack of directly comparable data on contaminant exposures in different tapwater sources, as well as document potential simultaneous mixtures exposures to inorganic, organic, and/or microbial contaminants of human-health concern. Over the course of seven cases studies, hundreds of point-of-use samples were taken from residental volunteers from geographical locations/communities of increased exposure susectability. This summary focuses on the results of the EPA-generated data from water sample extract analyses using in vitro effects-based methods, or bioassays, specific to endocrine disurption compounds. Overarching onclusions and implications based on biological activity detection patterns are provided. More broadly, the results support previous calls for continued systematic, quantitative assessments of contaminant exposures and associated bioactivities in tapwater, especially in unregulated and unmonitored locations, to support models of drinking-water contaminant exposures and related risks at the point of use. 

Description:

Effects-based bioassays are expeditious and economic non-targeted chemical analysis tools frequently used in preliminary stages of water quality monitoring efforts, or as part of effects-directed analysis. Using in vitro effects-based methods, we previously detected biological activity, indicative of endocrine disrupting compounds, in surface and source waters. However, there is a lack of contaminant occurrence data in unmonitored private-supply tapwater, and unknown adverse health effects from contaminant mixtures exposures. Therefore, USEPA and U.S. Geological Survey scientists collaborated with universities, Tribal, and non-profit partners to produce directly comparable occurrence data sets of public and private tapwater supplies, as well as of bottled water, to better inform consumer risk-management decisions at the point-of-use (POU). Community volunteers (POU water samples) across seven case studies in the US and Puerto Rico were selected based on exposure susceptibility (e.g., impacted source waters, geographical location, and aging distributions systems, among others). Using in vitro cell-based tools we developed a tiered screening process and tested solid phase-extracted water samples for biological activity. Estrogenic (T47d-KBluc; detected most often and in highest concentrations; ng Estradiol equivalents L-1) and androgenic activity (CV1-chAR; ng Dihydrotestosterone equivalents L-1) were detected in impacted source and private supply samples. Only one public-supply sample contained estrogenic activity above method detection limits; glucocorticoid (CV1-hGR) and antiandrogenic activity were not detected in any sample. Overall, estrogenic activity ranged 0.01 – 2.97 ng E2Eq L-1 (median: 0.05 ng E2Eq L-1), androgenic activity ranged 0.07 – 0.17 ng DHTEq L-1 (median: 0.15 ng DHTEq L-1). All estrogenic (3.8 ng E2Eq L-1) and androgenic (11 ng DHTEq L-1) detections fell below previously reported human-health Effects-Based Trigger values (for similar in vitro method) for drinking water. Consistent with our previous case studies, biological activity was detected most often in source waters, but contemporary treatment systems typically eliminate activity to below in vitro methods detection limits. However, private supplies sourced from ground water have potential to exhibit endocrine activity, especially when heavily impacted by local agriculture or anthropogenic waste. Abstract does not reflect Agency views or policy.

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