Public and Private Tapwater: Comparative Analysis of Contaminant Exposure and Potential Risk, Cape Cod, MA, USA

Humans are primary drivers of environmental contamination worldwide, including in drinking-water resources. In the United States (US), federal and state agencies regulate and monitor public-supply drinking water while private-supply monitoring is rare; the current lack of directly comparable information on contaminant-mixture exposures and risks between private- and public-supplies undermines tapwater (TW) consumer decision-making. Methods We compared private- and public-supply residential point-of-use TW at Cape Cod, Massachusetts, where both supplies share the same groundwater source. TW from 10 private- and 10 public-supply homes was analyzed for 487 organic, 38 inorganic, 8 microbial indicators, and 3 in vitro bioactivities. Concentrations were compared to existing protective health-based benchmarks, and aggregated Hazard Indices (HI) of regulated and unregulated TW contaminants were calculated along with ratios of in vitro exposure-activity cutoffs. Results Seventy organic and 28 inorganic constituents were detected in TW. Median detections were comparable, but median cumulative concentrations were substantially higher in public supply due to 6 chlorine–disinfected samples characterized by disinfection byproducts and corresponding lower heterotrophic plate counts. Public-supply applicable maximum contaminant (nitrate) and treatment action (lead and copper) levels were exceeded in private-supply TW samples only. Exceedances of health-based HI screening levels of concern were common to both TW supplies. Discussion These Cape Cod results indicate comparable cumulative human-health concerns from contaminant exposures in private- and public-supply TW in a shared source-water setting. Importantly, although this study’s analytical coverage exceeds that currently feasible for water purveyors or homeowners, it nevertheless is a substantial underestimation of the full breadth of contaminant mixtures documented in the environment and potentially present in drinking water. Conclusion Regardless of the supply, increased public engagement in source-water protection and drinking-water treatment, including consumer point-of-use treatment, is warranted to reduce risks associated with long-term TW contaminant exposures, especially in vulnerable populations.

Impact/Purpose

Current understanding of drinking-water contaminant exposures remains limited, in part, because routine compliance monitoring and more comprehensive chemical and biological investigations, in the United States and worldwide, are not commonly conducted at the point and time of consumption. Prior studies have documented multiple concerns and the need for expanded monitoring in private-well systems, however corresponding water quality data remain rare. Herein, the U.S. Geological Survey continues to collaborate with the USEPA, NIEHS, Colorado School of Mines, utilities, and others to fill drinking-water exposure data gaps in a range of source-water vulnerability settings. Specifically, Cape Cod private and public supplies rely on the same unconsolidated, surficial-aquifer source which has well-documented legacy and emerging anthropogenic contaminant concerns. Potential human-health risks from individual and aggregate TW exposures were explored based on multiple lines of evidence, namely cumulative detections and concentrations of designed bioactive chemicals, individual contaminant exposure exceedances of human-health benchmarks, and multiple hazard indices.

Citation

Bradley, P., D. LeBlanc, K. Romanok, M. Focazio, M. Cardon, J. Clark, J. Conley, N. Evans, C. Givens, J. Gray, E. Gray, Philip Hartig, C. Higgins, M. Hladik, K. Loftin, R. McClesky, C. McDonough, E. MedlockKakaley, C. Weis, V. Wilson, L. Iwanowicz, AND K. Smalling. Public and Private Tapwater: Comparative Analysis of Contaminant Exposure and Potential Risk, Cape Cod, MA, USA. Elsevier B.V., Amsterdam, NETHERLANDS, 152(106487):1, (2021). [DOI: 10.1016/j.envint.2021.106487]

DOI: Public and Private Tapwater: Comparative Analysis of Contaminant Exposure and Potential Risk, Cape Cod, MA, USA