Road salt may be a relatively harmless substance for people, but it may impact many species. That's the key warning of a risk assessment recently completed by the federal government.

"From a human health perspective, road salt is not an issue," says Bernard Madé. "The assessment focused on impacts of road salt on the environment. Certain species that live in and depend on certain environments just don't appreciate it."

Madé heads up the Chemicals Control Division of Environment Canada's pollution prevention office in Ottawa. It's his job to coordinate new management measures to help address some of the concerns raised through the assessment.

"We're working on guidelines and recommendations that will lead to better handling, storage and application of road salt," Madé explains. Because 90% of salt is applied at a large scale on roads, he says the key is to inform and educate municipal and regional authorities.

Road salt is a problem because it dissolves in runoff that finds its way into streams, irrigation systems and groundwater.

"The salinity of fresh water is altered with the introduction of chloride. This can have significant impacts on vegetation, especially agricultural crops," says Madé.

Runoff and spray from roads leads to an accumulation of salts in wetlands or groundwater. "Fresh water eventually flushes out to the oceans, but groundwater can take years or even decades before contamination levels come down."

Most road salt is derived from sodium chloride, identical to common table salt. Three other types of 'salt' are also used in road salt compounds, though less frequently: potassium chloride, calcium chloride and magnesium chloride.

Salt works because it lowers the freezing point of water. "By putting salt on the road in winter, it affects the freezing properties of snow and ice," Madé explains. "So you end up with slush you can remove or water that flows to the storm sewer."

In the Yukon, almost as much road salt is applied in summertime as in winter to help control dust on gravel roads. Because salt attracts and holds moisture, it keeps the road surface compacted and helps to reduce dust.

"We use about 2,000 tons of sodium chloride in winter, and about the same amount of calcium chloride in summer," says Robert Magnuson, the Director of Transportation with the Yukon government. "It sounds like a lot, but compared to the hundreds of thousands of tons of chlorides used in places like Ontario, we really don't use that much here."

For Madé, the challenge is making sure that operators applying road salt get the training and knowledge they need.

"We will not propose measures that could jeopardize road safety in the winter. The new guidelines will provide road authorities with a series of recommendations so they can put the right amounts in the right place at the right time," says Madé.

It used to be applied as rock salt, but techniques like spraying a pre-wetted chloride compound mean less salt is required and the action is faster. "It sticks where it falls," says Madé of the application. "Rock salt can bounce off the road."

Though certain other chemicals can be used as de-icers, Madé says that they are much more expensive. "Acetates are being looked at -- they have no chloride, and have fewer environmental challenges, but seem to be too costly to be used at a large scale at this point. Most of these alternative compounds are applied in small areas, or niches like airports."

"It's not likely chloride salts are going to be replaced, except in special areas where people are willing to pay more to protect a surrounding environment that is either particularly sensitive or has some higher value."

Magnuson says that road salt is just one of several products they use. They regularly experiment with other compounds, like magnesium and acetates. He agrees that they're more expensive, but says that some products are easier on the environment or better for certain applications.

Madé points out that climate has everything to do with the use of road salt.

"Freeze and thaw cycles drive the use of road salts. Much higher quantities are used in Atlantic Canada, southern Ontario and Quebec -- so it's more of an issue there."

Magnuson says that in the Yukon road salt is effective only to minus 6 or 8 Celsius. So it's not as widely used in dry, cold places like the Yukon and the Prairies. Instead, road crews apply sand and gravel to aid traction, and turn to salts during shoulder seasons to help break the bond between the ice buildup and the road.

Madé and Magnuson agree that road salt is just one tool intended to complement other methods. And if operators better understand the tools available to them, they expect fewer chlorides are needed to get the job done.