by Scott Smith, Communications Director
Road salt and table salt are basically one and the same: sodium chloride, or NaCL. And like Americans’ unhealthy love affair with salty food, we also dump way too much deicing salt on our roadways and sidewalks for our own good.
Across the U.S. each winter, around 27 million tons of sodium chloride are used to unfreeze roads and make them safer for travel. While application rates vary, roads in some of the icier regions may be treated with as much as 20 pounds of salt per square yard per year.
There’s no telling how much of that is wasted, but if you’ve lived anywhere in the 60 percent of the country that regularly receives snow, it’s a good bet you’ve seen whole piles of salt spilled by spreader trucks idling at intersections or have tip-toed across sidewalks and parking lots where the salt has been spread as thick as icing on a cake. (In truth, a single cup of road salt is enough to treat a 20-foot-long driveway – but more about that in a moment.)
First introduced in the late 1930s in New England, road salt works by lowering the freezing point of water, from 32 degrees F to about 15 degrees. Problem is, the use of deicing salts, which also include magnesium chloride and calcium chloride, has tripled over the past 45 years, leading to a troubling increase in salt concentrations in streams, rivers and lakes.
New research from the University of Toledo reveals that decades of overuse of road salts is threatening human health and the environment, contaminating drinking water supplies, mobilizing harmful chemicals such as lead and endangering the health of freshwater fish and aquatic plants and animals.
“The magnitude of the road salt contamination issue is substantial and requires immediate attention,” said Dr. Bill Hintz, assistant professor of ecology at UToledo and lead author of “Road Salts, Human Safety and the Rising Salinity of Our Fresh Waters,” published in November 2021 in the journal Frontiers in Ecology and the Environment.
Hintz and other researchers are finding that salting damages roadside vegetation, alters the hydrologic properties of soils and pollutes groundwater as it works its way into streams and rivers. Applying too much salt also shortens the life of pavements and hastens the corrosion of vehicles, bridges and other infrastructure. The researchers say overuse of road salts likely contributed to higher levels of corrosive chloride in the water supply in Flint, Mich., in 2014, leading to the release of lead from water distribution pipes. The New York Times reports that a separate 2018 study of wells in Dutchess County, N.Y., found that sodium concentration in drinking water from those 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.
Oversalting impacts the health of freshwater ecosystems across the North America. A study by the University of Toronto found that chloride concentrations — which highly correlate with road salt —in freshwater systems in the Greater Toronto Area exceeded established Canadian federal guidelines for protection of aquatic life even during the summertime.
Similarly, the UToledo researchers showed urban streams in the Great Lakes region had salt concentrations more than 20 to 30 times higher than the chronic chloride threshold of 230 milligrams per liter set by the Environmental Protection Agency. “Current EPA thresholds are clearly not enough,” Hintz said. “The impacts of deicing salts can be sublethal or lethal at current thresholds.”
How to make your home and community ‘Salt Smart’
Reducing your salt “footprint” at home will benefit your yard, pets and downstream waterways.
Sand can be a good substitute to provide traction, though it won’t help melt ice. Some municipalities and deicing suppliers are turning to beet juice, a biodegradable alternative that lowers the freezing point of water to below zero degrees. When combined with a small amount of salt and a sweetener like molasses, the briney solution turns sticky, which means it stays on the pavement longer, greatly reducing the total amount of salt needed. (Made from the white sugar beet, the mixture does not stain the roads, reports Tricia Drevets, writing for offthegridnews.com.)
Salt Smart Collaborative, a partnership among watershed-advocacy and transportation groups based in Illinois, provides salt-saving tips for both homeowners and commercial operations. Their common-sense advice for homeowners, including those with pets:
- First clear snow from driveways and sidewalks before it turns to ice;
- Distribute a small amount of salt evenly – a 12-oz. coffee mug of salt is more than enough to treat a 500 sq. ft. driveway;
- Better yet, check your local pet store or hardware store for pet-safe ice-melters; look for products that contain urea, propylene glycol or carbonyldiamide;
- Outfit your dog with boots and don’t let them drink from puddles that may contain salt, which can cause regurgitation and diarrhea;
- Rinse your dog’s paws if bootless or if they’ve tromped through any deicers your neighbors may have used;
- Make sure your own winter shoes have adequate traction; it’s also a good idea to wash your car following a storm that required deicing efforts.
The biggest payoff to reducing the use of road salt comes from municipal and commercial deicing operators, for the Toronto-based research group estimates that up to 10 times the appropriate amount of salt is commonly applied on parking lots and walkways.
U.S. cities across snowy climes are now treating roads before storms hit with a salt brine solution, which can lead to a 75 percent reduction in the total amount of salt used while keeping roads just as safe, according to the Cary Institute. Switching to a brine solution has allowed Jefferson County, Wis., to cut its salt use by up to 60 percent since 2018 without an increase in the number of accidents, reports the Times.
In addition to advocating for more efficient applications of brine mixtures, impactful solutions proposed by Hintz and the UToledo researchers include storing rock salt in covered structures with a concrete base; using snowplows equipped with multiple “live edges” with springs to better conform to road surfaces and post-storm assessments to monitor how salt was applied and to what effect.
A number of municipalities and organizations are emphasizing training and certification as the best approach to salt mitigation efforts. In New Hampshire, for example, the Green SnowPro Certification provides limited liability relief for snow removal contractors if they are certified, giving them legal coverage in the event they are sued for a slip or accident on treated surfaces. Says Hintz of these efforts: “Broad-scale adoption of best management practices is necessary to curb the increasing salinization of freshwater ecosystems resulting from the use of deicing salts.”
The ancient scribes warned of the devastation that comes with “salting the earth,” whereby a conquered enemy’s lands were sowed with salt to prevent any crops from growing ever again. Americans are at risk of doing that to our own selves by continuing the harmful, wasteful practice of overdosing the nation’s roadways with highly caustic compounds of salt.