What’s all that white stuff?

As winter sets in, Torontonians are once again becoming familiar with the white sheen left on their roadways after the streets have been salted. Rock salt is the most commonly used deicing agent in North America, dissolving precipitation on roads and lowering the freezing point to melt ice and snow. But what are its impacts on the environment?

Salt and deicing chemicals are carried by melting snow and ice onto vegetation and into soils and eventually into local rivers, streams, and other bodies of water. Some salts are transported directly to surface waters through drainage systems.

Toronto uses 201 salt trucks to distribute between 130,000 and 150,000 tonnes of salt annually over 5100 km of roads and 8200 kim of sidewalks. Growing concern over roadside habitat degradation, wildlife, and water quality in Canada prompted Environment Canada to conduct a comprehensive assessment of road-salt application to determine whether conventional deicers should be considered toxic substances under the Canadian Environmental Protection Act.

The end result? The five-year assessment by Environment Canada determined that in sufficient concentrations, road salts pose a risk to plants, animals, birds, lakes, ecosystems and groundwater.

Accordingly, the City of Toronto developed a salt management plan aimed at
optimizing the use of road salt and making significant changes to winter operations to better manage its use. Among the changes implemented were upgrades to equipment (resulting in better salt distribution and less waste), improved use of weather forecast information and improved training or staff who use salt.

Not all that comforting, is it? But what are the alternatives? One frequently used substitute is sand, which can be used to create friction to help melt snow and ice and provide vehicle traction. Sand is most often used in combination with small amounts of deicers. While there is no chemical harm in using sand, it is expensive to clean up and has other environmental impacts. Sand can blow off or be washed from roadway surfaces, clogging drainage systems. It can also be deposited in waterways and wetlands, impeding water flow and altering aquatic habitats.

Other alternatives include calcium magnesium acetate (CMA), a biodegradable material made from limestone and acetic acid, and potassium acetate (KA). CMA is biodegradable, and can thus be used in areas where roadside vegetation and surface waters are highly impacted by deicing chemicals. CMA is not as corrosive as road salt and can be applied to corrosion-sensitive structures like bridges and concrete surfaces. However, it is less effective at temperatures below -5º. Potassium acetate also carries a lower risk of corrosion and environmental impact and is longer lasting than most road salts, requiring fewer applications. Although both are preferable to road salt, they are much more expensive.

So what can we do? Try sprinkling sand on your sidewalk or walkway this winter instead of road salt. And whatever you use, do so in moderation. In addition to helping local ecological systems, you’ll track less salt onto your rugs and avoid excessive damage to your winter boots.