Tapwater Exposures, Effects Potential, and Residential Risk Management in Northern Plains Nations

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.

在美国（US），私人供水自来水（private-supply tapwater, TW）的监测工作极为匮乏。这一数据缺口严重制约了个体与社区的风险管理决策，导致依赖私人水井的农村及偏远地区出现未被察觉的污染物暴露的概率大幅上升。
我们针对北部大平原的三个原住民部落的使用点（point-of-use, POU）自来水开展了评估工作；该区域针对自来水砷（arsenic, As）的干预措施正持续推进，具体包括扩建小型社区供水系统，以及为强心水研究（Strong Heart Water Study）的参与者提供使用点吸附介质处理方案。
本研究共采集34个私人水井点位与22个公共供水点位的水样，对476种有机物、34种无机物以及3种体外生物活性指标进行了检测。最终检出63种有机物与30种无机物。其中，砷、铀（uranium, U）与铅（lead, Pb）的检出率分别为54%、43%与20%。
仅未处理的私人水井水样出现了超过公共供水最大污染物限值（maximum contaminant level, MCL）的浓度情况：砷的超标率为47%，铀的超标率为3%。而出于预防性健康目的设定的筛查限值则频繁被突破，主要诱因分别为私人供水水样中的无机物与公共供水水样中的氯基消毒副产物。
研究结果表明，同时暴露于多种共存的自来水污染物的情况十分普遍，因此有必要考虑扩大水源、入户点（point-of-entry）或使用点的水处理方案。本研究凸显了扩大私人供水自来水监测的重要性——采用覆盖范围广泛且具备环境信息价值的分析手段，可有效降低未被察觉的污染物暴露风险。