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Public and private tapwater: Comparative analysis of contaminant exposure and potential risk, Cape Cod, Massachusetts, USA

March 19, 2021


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.


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.


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.


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.


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.

Publication Year 2021
Title Public and private tapwater: Comparative analysis of contaminant exposure and potential risk, Cape Cod, Massachusetts, USA
DOI 10.1016/j.envint.2021.106487
Authors Paul M. Bradley, Denis R. LeBlanc, Kristin M. Romanok, Kelly Smalling, Michael J. Focazio, Mary C. Cardon, Jimmy Clark, Justin M. Conley, Nicola Evans, Carrie E Givens, James L. Gray, L. Earl Gray, Phillip C. Hartig, Christopher P. Higgins, Michelle Hladik, Luke R. Iwanowicz, Keith Loftin, R. Blaine McCleskey, Carrie A. McDonough, Elizabeth Medlock-Kakaley, Christopher P. Weis, Vickie S. Wilson
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental International
Index ID 70219120
Record Source USGS Publications Warehouse
USGS Organization California Water Science Center; Leetown Science Center; National Water Quality Laboratory; New Jersey Water Science Center; South Atlantic Water Science Center; Upper Midwest Water Science Center