Environmental researchers in the Greater Toronto Area say road salt runoff is making some local waterways as salty as seawater.
The salt is damaging the ecosystem, beginning to infiltrate ground water supply and has the potential to kill sensitive species, scientists warn.
"It's really quite worrying," Carl Mitchell, an associate professor of environmental science at University of Toronto, said in an interview.
"We're approaching ocean salt levels for certain amounts of time in some of these rivers," Mitchell told CBC Toronto.
"You can taste it at those levels."
Recent advances in testing technology have made it possible for scientists to track water quality in real time.
At Credit Valley Conservation (CVC), the authority responsible for protecting the Credit River watershed, salt levels at or above that of oceans have been recorded for periods following road salting.
Salinity is measured by tracking the chloride level of water.
According to CVC testing, during winter months, when road salting happens, chloride levels in streams consistently exceed 5,000 milligrams per litre.
"It's very, very high," said Amanjot Singh, a senior engineer with CVC.
"Some of the sensitive species will die."
Previously, researchers had to rely on "grab samples" taken directly from the water source. Now testing stations automatically send results every 15 minutes.
On Jan. 8, soon after four centimetres of snow fell in Mississauga, the chloride level of the Cooksville Creek was 18,000 mg/litre.
The average chloride level in oceans is 20,000 mg/liter.
Singh has seen chloride levels above 20,000 mg/litre in GTA rivers.
"We are worried," he said.
And the worry doesn't go away in the spring.
Singh says some GTA waterways, those in the most urbanized areas, never drop to what's considered a safe chloride level because of the accumulation of winter road salt in the soil and groundwater.
As urban sprawl in the GTA pushes closer to sensitive headwaters, Singh hopes municipalities can adopt alternatives to road salt, such as beet juice, or just cope with snowier roads.
Salt is 'cost effective'
But slowing down a city the size of Toronto isn't that simple.
Dominic Guthrie, a manager with the city's Winter Operations division, says road salt is the "agent" that allows residents to continue to safely move around the city in the snow.
"We're in a large urban environment and we rely on the movement of goods and services," Gutrie said.
As for alternatives, the city does use some beet juice, but it's more expensive than salt.
"It's not really cost effective to use beet juice for an entire season," Guthrie said.
But it isn't just local governments who are responsible for the brining of freshwater rivers and streams.
Elizabeth Hendriks, vice president of World Wildlife Fund Canada, says large private properties, such as big-box stores with big parking lots, contribute to the problem as well.
"It's building up," she said. "It's suffocating fish."
Hendriks says the high salt levels in rivers and streams are hurting many other species of wildlife, even raccoons.