Kristen Fisher, an environmental scientist with AECOM, warned that chloride from road salt, water softeners and certain fertilizers is accumulating in Wisconsin’s waters and posing ecological, health and infrastructure risks. Fisher said road salt (sodium chloride) is the largest single source in the state, and cited usage on the order of “about 1 to 2,000,000 tons per year” in Wisconsin since the 1950s.

Fisher described how dissolved chloride increases water density and can prevent seasonal mixing in lakes (a process she called a mechanism for long-term accumulation), leaving chloride to concentrate near lake bottoms where it is difficult to remove. She said a statewide graphic shows urbanized areas, including Milwaukee and parts of southern Wisconsin, with concentrations well above pre-salt levels.

Locally, Fisher pointed to the Yahara lakes in Dane County. She said road salt usage fell about 20% between 2019 and 2022, but chloride concentrations have continued to rise and can spike into the thousands of milligrams per liter during spring melt. Fisher added that two-thirds of Wisconsin residents rely on groundwater and that the U.S. Environmental Protection Agency has no health-based chloride standard; she cited the EPA’s secondary guideline of 250 mg/L as the level at which water begins to taste salty.

Fisher summarized ecological thresholds used by state agencies: she cited roughly 400 mg/L as a chronic toxicity point and about 757 mg/L for acute exposure, and noted that adverse effects on zooplankton have been observed at concentrations as low as 50 mg/L (reduced growth and reproduction). She also said amphibians such as spotted salamanders and wood frogs are "rarely found" in ponds with chloride above about 200 mg/L.

Beyond ecology, Fisher outlined human- and infrastructure-focused concerns. She said chloride can accelerate corrosion of pipes, bridges and vehicles and noted national estimates of billions of dollars in repair costs attributed to salt damage. She also referenced the role of high chloride in mobilizing lead in the Flint, Michigan drinking-water crisis as an illustrative extreme.

Household and small-scale responses Fisher listed include reverse osmosis, electrodialysis, distillation and deionization to remove chloride at the tap; she noted those treatments are expensive and uncommon at municipal treatment plants. For everyday behavior, she urged residents to follow Wisconsin SaltWise guidance: shovel before salting, scatter salt sparingly, switch products when salt is ineffective (salt loses effectiveness below about 15°F), and sweep up any leftover salt. As a rule of thumb she cited, "one coffee cup" of salt treats about 60 feet of sidewalk or a 20-foot driveway.

Fisher also called out water softeners and fertilizers as overlooked sources: she said backwash from salt-based home softeners enters wastewater or infiltrates groundwater and that potassium chloride fertilizers can contribute substantially to chloride loads (she cited a Minnesota study that attributed roughly 23% of chloride pollution there to fertilizer).

Fisher concluded by pointing listeners to Wisconsin SaltWise resources and local outreach (including a March 17 webinar and a children’s book used for education) and urged residents to reduce unnecessary salt use to protect lakes, groundwater and infrastructure.

The presentation contained multiple numerical references and local projections (for example, a municipal well projected to reach 250 mg/L within 17 years if current trends continue); those figures were presented by Fisher and are reported here as she stated them.