Road salt pickling Toronto rivers

Please don’t drink the run-off. Photo: Steve Davey

Tests found salt levels 140 times Ontario limits in Toronto’s rivers, according to a study carried out last winter. On March 27, Kevin Mercer, of Riversides Stewardship Alliance, released the results of river salt testing which the city conducted in December and January. In one case, samples of storm sewer discharge taken at a tributary of Mimico Creek, near Hwys 427 and 401, contained a salt concentration of 35,000 milligrams per litre  140 times the limit set by provincial water-quality standards.

“You might as well be pickling whatever lives or would like to live in that water,” said Mercer. “You couldn’t drink it. Provincial water-quality standards set 250 milligrams per litre as the limit for salt.” He called for city council to significantly reduce the 130,000 tonnes of salt Toronto crews put on roads each winter. He also wants the city to look at alternatives to road salt.

Environmentalists have requested Toronto’s works committee to endorse an Environment Canada report which classifies road salt as environmentally toxic.

A five year assessment by Environment Canada found that the five million tons of road salts used across the country every winter contaminate groundwater, surface water, poison wildlife and harm vegetation.

Streams, small lake ecosystems and groundwater are particularly vulnerable to road salt, which should be added to the Canadian Environmental Protection Act’s toxic substances list, Environment Canada said in its report.

Road salts are sodium chloride, calcium chloride, potassium chloride, magnesium chloride and ferrocyanide salts. The principal salt used on roads is the table salt used on food. The only irritation for humans from road salt is its adverse effect on the taste of contaminated roadside well waters, said the study.

Road salts enter the environment from storage facilities, through their applications to roads, streets and sidewalks and through the disposal of waste snow. Run off of meltwater from roads and releases from patrol yards where salts are stored have resulted in high concentrations of chloride in surface water, with concentrations greater than 1,000 milligrams per litre (mg/1).

Rainbow trout die after a week’s exposure to concentrations of 1,000 mg/1, and 10 percent of aquatic species are banned by prolonged exposure to chloride concentrations greater than 220 mg/1, Environment Canada estimates.

Sensitive fishes are harmed not only by the salt, but by the ferrocyanide used as an anti-caking agent to keep the salt from clumping together. The assessment found that reducing salt use or reducing the content of ferrocyanides in road salt formulations could reduce the risks to sensitive aquatic vertebrates in areas of high use of road salts.

High chloride concentrations in groundwater are of concern because the groundwater eventually surfaces at springs and contributes further to surface water contamination. Urban areas in Ontario, Quebec and the Maritime provinces of New Brunswick, Nova Scotia and Prince Edward Island where rock salt is used heavily during winter suffer most from contaminated ground and surface water.