MagChloride Truth


Compromising Aquatic Environments

To be included on the USFS QPL fully qualified list, long-term retardants must pass tests to confirm that their solution has low aquatic toxicity.

Colorado State University and Colorado Parks & Wildlife determined that the use of magnesium chloride on roadways can ultimately have detrimental effects on important aquatic benthic macroinvertebrates. Why does that matter? Aquatic macroinvertebrates are an important food source to fish, amphibians, and other wildlife. Negative impacts to aquatic macroinvertebrates were even measured at levels of exposure considerably lower than the EPA criteria for chloride. The authors recommended regulatory action be taken to manage application rates of mag chloride deicer to prevent the danger the chemical presents aquatic life. The researchers also noted that several communities in Colorado – including Aspen, Basalt and Summit County – already have taken action and banned the use of magnesium chloride road salts.


In November of 2022, the University of British Columbia launched a new study to determine whether road salt is contributing to salmon mortality in streams within the province. “Salmon start off in freshwater, and then they swim out to sea where there’s lots of salt … But it turns out that the baby fish in freshwater don’t handle it very well at all. It’s quite dangerous for them depending on the level,” said Professor Patricia Schulte, who is leading the five-year study. Schulte says research has determined that salt can harm Atlantic salmon, but this is the first study into how it is impacting Pacific salmon.

In an earlier study conducted by the Missouri Department of Natural Resources it was found that even at low levels, chloride can negatively affect aquatic life structure, diversity and productivity. When levels are high, it says chloride is toxic to fish, aquatic organisms and amphibians.

The studies and ongoing research summarized above focused on the impact chloride and road salt have on aquatic life make findings from a study conducted by the United States Geological Survey even more disturbing. In their research, the Agency found that 84% of the urban streams they studied had rising chloride levels, and 29% had already exceeded federal safety guidelines for at least part of the year. The USGS attributed the increase to the use of road salt. Meanwhile, the US Environmental Protection Agency has reported that, “When compared on the basis of mg of chloride/L the chlorides of potassium, calcium and magnesium are generally more acutely toxic to aquatic animals than sodium chloride.” Once chloride enters a waterway, there isn’t a biological process that will help remove it, so as more of it is added to our waterways the problem only becomes worse.