Citation:

Bradley, P., D. Kolpin, D. Thompson, K. Romanok, K. Smalling, S. Breitmeyer, D. Cwiertny, N. Evans, R. Field, M. Focazio, L. Freeman, C. Givens, J. Gray, G. Hager, M. Hladik, J. Hofmann, R. Jones, L. Kanagy, R. Lane, R. McCleskey, D. Medgyesi, E. Medlock Kakaley, S. Meppelink, M. Meyer, D. Stavreva, M. Ward, AND M. Cardon. Juxtaposition of Intense Agriculture, Vulnerable Aquifers, and Mixed Chemical/Microbial Exposures in Private-Well Tapwater in Northeast Iowa. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 868:161672, (2023). https://doi.org/10.1016/j.scitotenv.2023.161672

Impact/Purpose:

The current results address a critical lack of directly comparable data on broad contaminant exposures in TW in agriculturally-developed settings and document commonplace simultaneous exposures to inorganic, organic, and microbial contaminants of human-health concern. The results support incorporation of well-maintained, residential treatment systems as prudent protection against unrecognized contaminant exposures in private well homes, including in agriculturally-developed areas. Several point-of-use treatment technologies are effective in reducing tapwater exposures to many of the contaminants identified in this study. More broadly, the results support previous calls for continued systematic, quantitative assessments of contaminant exposures and associated bioactivities in tapwater, especially in unregulated and unmonitored locations, to support models of drinking-water contaminant exposures and related risks at the point of use.

Description:

ABSTRACT: In the United States and globally, contaminant exposure in unregulated private-well point-of-use tapwater (TW) is a recognized public-health data gap and an obstacle to both risk management and homeowner decision making. To help address the lack of data on broad contaminant exposures in private-well TW from hydrologically-vulnerable (alluvial, karst) aquifers in agriculturally-intensive landscapes, samples were collected in 2018-2019 from 47 northeast Iowa farms and analyzed for 437 unique organics, 35 inorganics, 5 in vitro bioassays, and 11 microbial assays. Fifty-one organics, dominated by pesticides and related transformation products (35 herbicide-, 5 insecticide-, and 2 fungicide-related), and 26 inorganics were observed in TW. Heterotrophic bacteria detections were near ubiquitous (94% of the samples), with detection of total coliform bacteria in 28% of the samples and growth on at least one putativepathogen selective media across all TW samples. Precautionary health-based hazard indices (HI) screening levels were exceeded frequently in private-well TW and attributed primarily to inorganics (nitrate, uranium). Results support incorporation of residential treatment systems to protect against contaminant exposure and the need for increased monitoring of rural private-well homes. Continued assessment of unmonitored and unregulated private supply TW is needed to model contaminant exposures and human-health risks.

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