Road salt works, but environmental costs mount
Salt used for de-icing is making its way into freshwater ecosystems
As snowstorms sweep the East Coast of the United States this week, transportation officials have deployed a go-to solution for keeping winter roads clear: salt.
But although pouring tons of salt on roads makes winter driving safer, it also has damaging environmental and health consequences, according to a growing body of research.
As snow and ice melt on roads, the salt washes into soil, lakes and streams, in some cases contaminating drinking water reservoirs and wells. It has killed or endangered wildlife in freshwater ecosystems, with high chloride levels toxic to fish, bugs and amphibians, according to the Environmental Protection Agency.
“It’s an issue that requires attention now,” said Bill Hintz, an assistant professor in the environmental sciences department at the University of Toledo and the lead author of a recent research review published in the journal Frontiers in Ecology and the Environment.
“There’s plenty of scientific evidence to suggest that freshwater ecosystems are being contaminated by salt from the use of things like road salt beyond the concentration which is safe for freshwater organisms and for human consumption,” Hintz said.
Salt has been used to de-ice roads in the United States since the 1930s, and its use across the country has tripled in the past 50 years, Hintz said. More than 20 million metric tons of salt are poured on U.S. roads each winter, according to an estimate by the Cary Institute of Ecosystem Studies in New York, and the environmental costs are growing.
Still, little has been done to address the environmental impact of road salt because it is cheap and effective, said Victoria Kelly, environmental programming manager at the Cary Institute. By lowering the freezing temperature of water, salt prevents snow from turning to ice and melts ice that is already there.
Road salt is made from sodium chloride, the same chemical found in table salt. Of all salt consumed in the United States, about 43 percent is used for highway de-icing, according to the U.S. Geological Survey in 2020.
The consequences of insufficiently salting roads were seen this week, when hundreds of drivers were stranded by a snowstorm on Interstate 95 in Virginia. Officials said the storm began with rain, which washed away road salt and made it difficult to keep roads clear.
Environmentalists say the problems associated with road salt are getting harder to ignore. A 2018 study of wells in Dutchess County, N.Y., found that sodium concentration in wells reached levels as high as 860 milligrams per liter — much higher than the federal and state recommendation that levels not exceed 20 milligrams per liter for people on very low-sodium diets and 270 milligrams per liter for people on moderately restricted sodium diets.
A separate 2018 study in the journal Environmental Science and Technology showed 24 percent of private drinking wells in New York were contaminated with salt that had been used on roads.
Last month, New York Gov. Kathy Hochul announced appointments to the Adirondack Road Salt Reduction Task Force, established to review road-salt contamination.
Road salt also corrodes vehicles and bridges, causing $5 billion in annual repairs in the United States, according to an EPA estimate.
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