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.
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