Salt. We consume it, we once used it as currency, and we use it to deice roads and sidewalks. Deicers used in the U.S. include acetates, chlorides, and, rarely, DIY versions, sometimes involving pickle juice or cheese brine, according to the Minnesota Stormwater Manual.

Salt Smart Collaborative states that Sodium chloride, the most common type of deicer, works by dissolving into the water and breaking into separate sodium and chloride ions, disrupting the bonds between water molecules, which causes the water to remain in liquid form. 5,000 tons of salt were used for roads in a year in the 1940s, but that number has grown exponentially. Today, about 20 million tons of salt are spread in the U.S. annually. Salt and other deicers have something in common besides their deicing properties: they are all extremely harmful pollutants.

Remember how sodium chloride breaks into separate ions in the deicing process? Well, chloride by itself is devastating to aquatic ecosystems. Soil doesn’t retain chloride ions because of their negative charge, so they make their way to bodies of water or aquifers, where there is no natural way of removing them. At a certain concentration, which some of Minnesota’s bodies of water exceed, chlorides deplete oxygen and affect wildlife growth and reproduction, making the water uninhabitable to fish and aquatic life. Unfortunately, 30% of road salt applied in the Twin Cities Metro Area makes its way to the Mississippi River, according to the Minnesota Stormwater Manual, while the rest collects in lakes, wetlands, and groundwater.

Road salt also increases water salinity, or saltiness, reducing aquatic species’ fitness and survival. A 2014 Geological Survey found that 84% of northern U.S. streams had rising salinity levels. All deicers, even pickle juice, have negative environmental impacts, and some cause infrastructure damage.
Chloride salts and many other deicers have corrosive effects on steel or galvanized steel, causing water infrastructure damage across the country. Plus, salt degrades concrete, causing cracks and crumbling over time.

It is important to note that deicing plays a critical role in keeping people safe in the winter, reducing vehicle accident costs by 88%, according to a Marquette University Study. Although it would be impractical to stop chemical deicing, the process still needs to be moderated. Even the government has realized the effects of salting on the environment.

Since the 1960s, Minnesota has restricted salt usage, implementing salt regulators in plow vehicles and brine for a lower concentration of salt, and the current statute, section 160.215, limits where salt can be applied, reducing, but not eliminating, chemical deicing. Citizens dealing with winter weather can limit salt pollution by shoveling, using a snowblower, or using sand for traction when it’s too cold for chemical deicers, though sand still contaminates waterways, often worse than salts do, and it also pollutes the air. If using salt on the sidewalk is necessary, consider distributing it sparingly and collecting and reusing the salt left behind when the snow clears. Everyone can do their part to keep as much salt as possible out of Minnesota’s soil, surface water, and groundwater.