Using road salt to keep streets clear in winter is effective, but there are harmful impacts
One of the most harmful things about winter is the white stuff that covers our roads and sidewalks. We’re not talking about snow, but rather the road salt that is used whenever snow falls on our roads.
Each year the City of Toronto lays down up to 150,000 tonnes of salt on its approximately 5,100 kilometres of roads. It’s used to control snow and ice so that driving, walking and getting around in general can be safer.
Salt is popular with municipalities and contractors because it’s cheap and easy to distribute. But, where road salt is concerned, there is plenty to worry about. One problem is that it doesn’t always work. Salt is used to lower the freezing point of water to make it harder for ice to form, but it only works when temperatures are above -7 C. When temperatures fall below that, the city applies brine – a salt and water mixture – ahead of the snowfall, in order to restrict the ability of water and snow on roads to freeze.
Road salt is also harmful to the environment. In 2001, Environment Canada published the results of a five-year assessment on the impacts of road salts, noting it had an adverse effect on freshwater ecosystems, soil, vegetation and wildlife. In March 2021, the University of Toronto published the results of a study that looked at the impact of road salt on aquatic habitat in the city’s rivers. It found that salt run-off in the spring was causing negative impacts well into the summer.
“Of the samples we took from four GTA rivers and creeks during the summer, we found that nearly 90 per cent exceeded federal guidelines for long-term exposure of aquatic life to chloride,” said Donald Jackson, a professor of aquatic ecology in the department of ecology and evolutionary biology.
Similar findings across the southern Great Lakes have been found by WWF Canada. Its studies have revealed that many urban and rural waterways in southern Ontario are showing record high chloride levels. Some are even as salty as the ocean in the winter, according to WWF’s data.
“Ontario is over-salting its parking lots, sidewalks and roadways,” said Elizabeth Hendriks, vice-president of freshwater with WWF Canada. “A small pill bottle or saltshaker is all that’s needed to melt the equivalent of a city sidewalk slab.”
Beyond environmental issues, road salt is corrosive and can damage vehicles, stains shoes and clothing, and can damage lawns during the spring melt.
The drawbacks of road salt are compelling municipalities and contractors to find ways to minimize its use. Some municipalities are also experimenting with alternative products to see if salt can be replaced altogether. In 2016, the City of Toronto produced a Salt Management Plan, which included a list of ways the use of salt can be reduced. Examples include improved training of operators and fitting more trucks with anti-icing and pre-wetting equipment.
In an email, Hakeem Muhammad, transportation spokesperson for the city, said road salt continues to be the best and most effective way to keep roads safe in winter weather. However, the city is aware its use is associated with negative environment impacts. City staff work to reduce those impacts as much as possible by actively managing salt use, Muhammad said, adding it aims for a 10 to 15 per cent reduction by pre-wetting the salt so less is required.
“Salt spreaders are calibrated at the beginning of each winter season and operators are being continuously trained,” Muhammad said. “New equipment will be purchased as part of the new winter services contracts starting in the fall of 2022, which will be more efficient in their salt usage.”
For private contractors, best practices for salt management can be learned through Smart About Salt, a not-for-profit agency. Its online training and certification programs provide advice on how to minimize the use of salt to save money and help the environment at the same time.
Alternatives to road salt exist and continue to be explored. The Sustainable Technologies Evaluation Program – a collaboration between the Credit Valley, Lake Simcoe region and Toronto region conservation authorities — has conducted research on various alternatives. These can be broken down into three categories: chloride de-icers, acetate de-icers, and agricultural byproducts (organics). The research concluded that all the alternatives have drawbacks, including higher prices, specific application requirements, lack of effectiveness and associated environmental issues.
A 2014 study by the University of Waterloo, in partnership with the Toronto and Region Conservation Authority, looked at organic and semi-organic alternatives. The study determined that organic anti-icers had lower chloride and sodium levels, but contained higher levels of nutrients and organic carbon. When temperatures drop below -20 C, Toronto spreaders use a de-icer made from a mixture of sugar beet molasses and (much less) salt. In Wisconsin, the salty brine from making mozzarella cheese has been used for several years and has had positive effects.
Another alternative are traction agents. Sand is often used this way in rural areas where salt isn’t effective. There are also organic traction agents, such as EcoTraction, a product derived from volcanic rock. It can be used on its own by homeowners or mixed in with de-icers and spread on roads or parking lots by municipalities and contractors.
Keyword: A salty balance