Road salt is keeping drivers safe but harming the environment, researchers say

Sprinkling salt on the road or sidewalk after snowfall can make conditions safer for drivers and pedestrians, but can cause harm to local waterways and wildlife, London, Ont., researchers say.

People studying salt pollution are calling on cities and residents to consider the type and amount of salt they use this winter.

"It's still something that we need to use for safety and getting around, it's not an avoidable thing, but we can reduce the amount of salt we use," said Taryn Smit, an ecologist volunteering with Canadian Conservation Corps, who recently completed a project studying road salt pollution. 

The salt used on the road is often the same salt that people have at the dinner table, said Smit: sodium chloride. Salt helps to lower water's freezing temperature, meaning that it prevents ice from forming and helps melt ice already on the road.

"Eventually when the snow melts, all that salty water runs into our streams and rivers," Smit said. 

When organisms, like fish or frogs, are in freshwater with too much salt, they cannot maintain the necessary balance between salt and water in their bodies, Smit said. 

"Think about if you have not had enough water and now you're starting to get headaches, feel sick and dehydrated," said Smit. "The same kind of process will happen with anything that lives in the stream of the river because there's salt in the water."

This can cause them to become sick or die, Smit said, which can then cause a chain reaction in an ecosystem.

Smit said there are some unexpected creatures that are impacted by salt pollution, including deer who are attracted to salt on the roads which can make them more susceptible to getting hit by cars.

Reducing salt usage

In the Upper Thames River, Smit said rural parts of the watershed are doing "pretty well" with salt levels, but there are a few closer to urban locations with salt levels that are close to passing federal guidelines for too much salt.

Cities and their residents should be reducing the amount they use, she said. She recommends first shoveling the snow and clearing the ice before spreading a one tablespoon of salt per square metre. After the snowfall is over, there is still another step.

"Once it's done its job and you're not expecting any more ice, you can sweep that salt up, put it in a bucket, keep it and use it again," said Smit. "That's also a way to use less salt for your pocket to save money."

Salt and corrosion 

Researchers at Western University are also looking into road salt sustainability, specifically focusing on how road salt can corrode metal and concrete.

"We're basically looking at the corrosion behaviour of salt against metals, the environmental impact the salt can cause, the ice melting performance of salt and the costs," said Robert Addai, a PhD candidate at Western who is part of the study.

"Maybe you get cheap salt today but the cost of repairing corrosion and the environment in the future may be higher," he said.

While the research is still in progress, Addai said his work so far has included looking into nine different types of salt to find out which is the most environmentally friendly. He said that all salts corrode, but inorganic salts such as the commonly-used sodium chloride cause less damage by primarily corroding metal.

Using a mixture of different types of salts can cause even more damage, Addai said, as they end up corroding both metal and concrete.

"Organic salts are corroding the concrete and the cost of repairing concrete is more than the cost of repairing metals," Addai said. "It's good that we stick to the inorganic salt like sodium chloride and calcium products we have been using."