Exposures and potential health implications of contaminant mixtures in linked source water, finished drinking water, and tapwater from public-supply drinking water systems in Minneapolis/St. Paul area, USA

Continued improvements in drinking-water quality characterization and treatment/distribution infrastructure are required to address the expanding number of documented environmental contaminants. To better understand the variability in contaminant exposures from the drinking water resource (surface and groundwater), through the distribution process, to the point-of-use (tapwater, TW), in 2019 a synoptic assessment of broad chemical exposures was conducted in system-specific source waters, pre-distribution and service-area TW from 10 drinking water treatment plants in the greater Minneapolis/St Paul area of Minnesota, United States. Source and TW samples were analyzed for 465 unique organic compounds, 34 inorganic constituents, and 3 field parameters as well as in vitro estrogen, androgen, and glucocorticoid bioactivities. Mixtures of organic and inorganic contaminants were prevalent in source water and TW samples, indicating the continued need for broad assessments of mixed contaminant exposures to characterize potential drinking-water human health outcomes. Contaminant concentrations were similar among drinking water sources and no exceedances of Environmental Protection Agency maximum contaminant levels (MCL) were observed in any treated TW sample in this study; the latter indicting broad regulatory compliance and effective treatment. No TW sample contained estrogenic, androgenic or glucocorticoid activity at concentrations that may cause adverse human health effects. However, multiple exceedances of non-enforceable MCL goals (MCLG) and other health advisories combined with frequent exceedances of benchmark-based hazard indices indicated potential aggregated risks to vulnerable subpopulations and emphasizes the continued need to assess contaminant mixture exposures at the drinking-water point of consumption using a broad analytical scope.

Impact/Purpose

Compliance monitoring, regulation, and treatment of public supply drinking water in the United States and elsewhere provide human health benefits, but recent studies have shown that an increasing number of unregulated contaminant mixtures break through the existing treatment processes and are observed in both treated pre-distribution and tapwater samples. Current research has focused on informing the public health data gap on exposures to a wide range of regulated and unregulated contaminants at the point-of-use (i.e., homes, workplaces, and schools). Herein the USEPA continues its collaboration with the U.S. Geological Survey,  National Institute of Environmental Health Science (NIEHS), and Minnesota Department of Health to inform exposure to a wide range of contaminants in drinking water at the point-of-use.  Studies conducted to date have assessed contaminant mixtures in both public and private supply in a range of socioeconomic and source water vulnerability settings across the US. In this case study the goal was to to better understand how contaminant mixtures change as they move from drinking water resources (surface and groundwater), through the distribution process and to the tap,

Citation

Smalling, K., P. Bradley, K. Romanok, S. Elliot, J. de Lambert, M. Focazio, S. Gordon, J. Gray, L. Kanagy, M. Hladik, K. Loftin, R. McCleskey, E. Medlock Kakaley, M. Cardon, N. Evans, AND C. Weis. Exposures and potential health implications of contaminant mixtures in linked source water, finished drinking water, and tapwater from public-supply drinking water systems in Minneapolis/St. Paul area, USA. Royal Society of Chemistry, Cambridge, UK, 9:1813-1828, (2023). [DOI: 10.1039/D3EW00066D]

DOI: Exposures and potential health implications of contaminant mixtures in linked source water, finished drinking water, and tapwater from public-supply drinking water systems in Minneapolis/St. Paul area, USA