More than one-third of public wells in Wisconsin tested for sodium over the past decade exceeded the recommended limit for individuals on low-sodium diets, according to newly analyzed data from the Wisconsin Department of Natural Resources (DNR). The findings highlight a potential health risk in a state where more than a million adults live with high blood pressure, a condition closely linked to excessive sodium intake.
Between 2014 and 2024, the DNR tested 1,762 public wells, including those serving cities, towns, apartment buildings, and other shared water systems. Of those, 626 wells—or 36%—had sodium levels above 20 milligrams per liter (mg/L), the threshold recommended by the Wisconsin Department of Health Services for people following low-sodium diets. While sodium is an essential mineral for human health, consuming it in excess can elevate blood pressure and exacerbate conditions like kidney disease or heart problems.
Sodium can enter drinking water from various sources, including naturally occurring rock formations, water softeners, and road salt. While the data does not pinpoint the specific contribution of each source, DNR experts believe road salt plays a significant role.
Carla Romano, the DNR’s groundwater section manager, noted that road salt is a controllable contributor to sodium in water. Road salt, widely used in Wisconsin's snowy winters, poses risks not only to human health but also to freshwater ecosystems.
Each year, Lake Michigan receives an estimated 2.2 billion pounds of chloride, a component of road salt. Chloride concentrations in the upper Mississippi River rose by 35% between 1989 and 2018, and smaller waterways like Milwaukee's Kinnickinnic River have experienced chloride levels toxic to aquatic life. Unlike other pollutants, chloride does not break down over time, leading to long-term environmental impacts.
In efforts to prevent slippery pavements, many people unknowingly use excessive amounts of road salt. However, experts recommend just a coffee mug’s worth of salt for 10 sidewalk squares or a 20-foot driveway. Salt becomes ineffective at melting ice when temperatures fall below 15°F.
While public awareness of road salt’s environmental impact has grown, DNR stormwater section manager Shannon Haydin remains concerned that the potential health consequences are less understood.
The DNR plans to conduct further analysis to determine which areas of the state have disproportionately high sodium levels in their drinking water. Investigations will also focus on wells that have repeatedly tested above the recommended limit and identify sources contributing to elevated sodium levels.
Wisconsin State Senator André Jacque, who previously introduced legislation to reduce over-salting on private property, described the findings as alarming. "Even unconsciously, people are seeing the effects of salt as a contaminant—not just in terms of taste, but in its broader impacts," Jacque said.
Individuals on low-sodium diets who are concerned about their drinking water quality should consult with their doctor, contact their local water utility, or test their private wells if applicable. The issue underscores the need for ongoing efforts to balance winter safety with public health and environmental protection.
The Wisconsin Department of Natural Resources (DNR) and Wisconsin Salt Wise invite the public to learn more about the impacts of road salt on drinking water and freshwater ecosystems during Winter Salt Awareness Week, running Jan. 27-31.
Winter Salt Awareness Week will include a series of YouTube livestreams featuring speakers and topics focused on the true impacts of salt and ways to be a freshwater advocate.
Speakers include Abby Hileman (Izaak Walton League of America), Jess Hua (University of Wisconsin-Madison), public works professionals from across the country, and a panel of experts providing salting policy perspectives from New Hampshire, Ohio, and Minnesota.
Register in advance at https://wintersaltweek.org/register/ or watch afterward on the Wisconsin Salt Wise YouTube Channel @wisaltwise1739
Photo credit: iStock/Steven White
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