Nelson Issue Brief: Nitrate contamination in drinking water and groundwater


Safe drinking water has become a major bipartisan priority in Wisconsin. Governor Tony Evers has declared 2019 the year of Safe Drinking Water and Assembly Speaker Robin Vos has commissioned a taskforce on water quality. This inaugural edition of the Nelson Institute for Environmental Studies Issue Brief focuses on the most widespread groundwater contaminant: Nitrates. This is an environmental and public health hazard faced by Wisconsinites statewide.

Map showing nitrates detected by township in Wisconsin
Nitrate levels are too high in wells used by an estimated 94,000 Wisconsin households that have private water wells. Agricultural areas and those with porous bedrock or sandy soil are most susceptible to nitrate contamination. It comes from fertilizers, including manure and other sources. Credit: Katie Kowalsky, Wisconsin Center for Investigative Journalism. Source: Well Water Quality Viewer, University of Wisconsin-Stevens Point’s Center for Watershed Science and Education. Private Drinking Water Quality in Rural Wisconsin, Journal of Environmental Health, 2013. View a larger version of this map

The great majority of the state’s drinking water comes from groundwater wells, and approximately 940,000 households are served by 676,000 private wells for which no testing is generally required. The state’s Groundwater Coordinating Council estimates that 42,000 private wells across the state have nitrate concentrations above 10 parts per million — the level considered unsafe for consumption by the U.S. EPA.

The Wisconsin Department of Health Services (DHS) considers nitrate exposure at this level to pose a serious risk of metabolic and neurological disorders in infants. In addition, DHS cites that some studies suggest that high levels of nitrates may be linked to birth defects, thyroid problems, and certain kinds of cancer.

UW–Madison faculty are doing research relevant to this public health and environmental challenge, and are available to local governments and state leaders as they consider the ways to limit groundwater contamination while minimizing impacts to farm income and residential property rights.

We hope these research summaries will stimulate linkages between the UW community and Wisconsinites statewide who are facing water quality problems and looking for answers grounded in world-class research. Please reach out to the researchers highlighted in this report if you have further questions about their work.

Key points

Learn more about nitrate contamination

Additional resources