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FACT BRIEF

Are chloride levels increasing in Wisconsin waterways because of road salt use?

By Hope Karnopp
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YES

According to the Wisconsin Department of Natural Resources, chloride concentrations in 26 of Wisconsin's largest river systems increased from 600,000 tons in the early 2000s to 800,000 tons in 2018.

The department said the rise is "partly due to road salting" but also cited water softeners and fertilizers as factors.

The department set the toxicity threshold for aquatic life at 395 mg/L. The EPA's secondary standard for chloride in drinking water (based on taste and smell, not health) is 250 mg/L. A map shared by WI Salt Wise shows parts of Wisconsin already exceed these limits, particularly in central and southeastern Wisconsin.

The issue of elevated chloride levels extends beyond Wisconsin: researchers from the U.S. Geological Survey found that chloride concentrations "increased substantially" in 84% of urban streams studied between 1960 and 2011 in multiple states.

This fact brief is responsive to conversations such as this one.
Sources
Wisconsin Department of Natural Resources Reduce Salt Use This Winter
WI Salt Wise Hidden Costs of Oversalting
WI Salt Wise Road Salt Report
U.S. Geological Survey Evaluating chloride trends due to road-salt use and its impacts on water quality and aquatic organisms
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Wisconsin Watch, the news arm of the nonpartisan, nonprofit Wisconsin Center for Investigative Journalism, increases the quality and quantity of investigative reporting in Wisconsin, while training current and future investigative journalists. Its work fosters an informed citizenry and strengthens democracy.
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Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact —a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all fact briefs here.