Kristin M. Romanok Kelly L. Smalling Michael J. Focazio Robert Charboneau Christine Marie George Ana Navas-Acien Marcia O’Leary Reno Red Cloud Tracy Zacher Sara E. Breitmeyer Mary C. Cardon Christa K. Cuny Guthrie Ducheneaux Kendra Enright Nicola Evans James L. Gray David E. Harvey Michelle L. Hladik Leslie K. Kanagy Keith A. Loftin R. Blaine McCleskey Elizabeth Medlock-Kakaley Shannon M. Meppelink Joshua F. Valder Christopher P. Weis Paul M. Bradley 2022 <p><span>In the United States (US), private-supply tapwater (TW) is rarely monitored. This data gap undermines individual/community risk-management decision-making, leading to an increased probability of unrecognized contaminant exposures in rural and remote locations that rely on private wells. We assessed point-of-use (POU) TW in three northern plains Tribal Nations, where ongoing TW arsenic (As) interventions include expansion of small community water systems and POU adsorptive-media treatment for Strong Heart Water Study participants. Samples from 34 private-well and 22 public-supply sites were analyzed for 476 organics, 34 inorganics, and 3 in vitro bioactivities. 63 organics and 30 inorganics were detected. Arsenic, uranium (U), and lead (Pb) were detected in 54%, 43%, and 20% of samples, respectively. Concentrations equivalent to public-supply maximum contaminant level(s) (MCL) were exceeded only in untreated private-well samples (As 47%, U 3%). Precautionary health-based screening levels were exceeded frequently, due to inorganics in private supplies and chlorine-based disinfection byproducts in public supplies. The results indicate that simultaneous exposures to co-occurring TW contaminants are common, warranting consideration of expanded source, point-of-entry, or POU treatment(s). This study illustrates the importance of increased monitoring of private-well TW, employing a broad, environmentally informative analytical scope, to reduce the risks of unrecognized contaminant exposures.</span></p> application/pdf 10.1021/acsestwater.2c00293 en American Chemical Society Tapwater exposures, effects potential, and residential risk management in Northern Plains Nations article