Emerging Contaminants in Source and Finished Drinking Waters Across Minnesota (U.S.) and Potential Health Implications

Relatively little data exist regarding the presence of unregulated contaminants in drinking waters. We sampled source and finished drinking water from 98 community water supply systems throughout Minnesota (U.S.). Facilities were grouped into four networks based on water source and influences from anthropogenic activities. Measured contaminants were dependent on network and included some combination of pesticides, pharmaceuticals, per- and poly-fluoroalkyl substances (PFAS), benzotriazoles, hormones, wastewater indicators, and illicit drugs. Overall, the number of contaminants detected in samples ranged from 0 to 35 and concentrations ranged from 0.38 ng/L (progesterone) to 47,500 ng/L (bromoform). Fewer contaminants and lower concentrations were detected in finished water samples, compared to source waters. Significantly (<i>p</i> < 0.05) more PFAS and pesticides and higher sample total concentrations were observed in wells designated as vulnerable to contamination. To estimate potential human-health risk from exposure in drinking water, concentrations were compared against bioactivity information from the U.S. Environmental Protection Agency's ToxCast database and state-based guidance values, when available. Although comparisons could be made for relatively few contaminants, concentrations in finished waters were at least an order of magnitude lower than screening thresholds. Results from this study were used to inform enhancement of the Minnesota Department of Health's drinking water protection program.