​Nobody knows how blue crabs got into Toronto’s Mimico Creek, but the more interesting question is how some of them survived in it.

The blue crab is a saltwater creature, yet six apparently healthy ones were found in the freshwater creek in 2011. And while the water wasn’t salty enough for them to breed, it made for comfortable living. The crabs’ survival illustrates a growing problem for Ontario’s waterways: the excessive salting of roads, sidewalks, and parking lots has contaminated rivers, streams, and lakes.

Road salt is a necessary evil, effective in deicing roads, sidewalks, and parking lots, and in improving safety at certain temperatures. But in Ontario, it’s common to use much more than necessary, which leads to crunchy sidewalks and runoff that makes lakes and rivers saltier.

“We could probably reduce the amount of salt we’re applying by at least 25 per cent,” says Tim Van Seters, senior manager with the Toronto Region Conservation Authority. “We’re not going to get rid of it altogether. That’s not realistic to think — but we could certainly reduce it much more by putting in the right safeguards.”

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Salt pollution does much more than provide habitable waters for strange creatures. Increased salinity is harmful to many freshwater organisms, right down to the tiny invertebrates that underpin the entire food chain. Salt is also bad for many native plants and can contaminate groundwater.

Van Seters has been watching Toronto’s rivers and creeks since 2002, when he started working as the water-quality coordinator for the TRCA. The authority monitors chlorides across the watershed (the chloride part of salt is what causes problems). Guidelines state that chronic exposure to chloride in freshwater streams is concerning above 120 milligrams per litre, and acute exposure above 640 milligramts per litre. Mimico Creek regularly tests above 25,000 milligrams per litre in the winter, according to Van Seters. (By comparison, seawater contains roughly 35,000 milligrams per litre.)

But salt doesn’t only cause problems in winter, Van Seters says: chlorides can build up in groundwater and stormwater reservoirs, leading to year-round waterway contamination.

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Environment Canada completed a five-year study in 2001 that concluded road salt should be added to its list of toxic substances, although the department did not actually ban the use of road salt. It also stated that any measures taken in response to the study should be “based on optimization of winter road maintenance practices so as not to jeopardize road safety, while minimizing the potential for harm to the environment .”

While provincial and municipal crews can be directed by policy, much snow removal is done by private contractors, which makes it difficult to monitor and control how much salt is applied to Ontario’s roads.

“There’s quite a lot of parking lots in the GTA, and a huge amount of salt is applied to those areas. Anyone can go out in a truck, put salt in the back of their truck and spread it in whatever quantities they want,” says Van Seters. “There’s no regulation as to how that’s done, and there really should be. There should be some kind of certification or some kind of licensing requirement just as there is for pesticides or anything that might be toxic.”

Van Seters says new salt-spreading equipment could also help: automated spreaders are capable of moderating the amount of salt laid down and can help contractors monitor their application rates.

New Hampshire was the first U.S. state to use rock salt (that is, sodium chloride) on its roads, and it’s ahead of the curve when it comes to moderating use of the stuff, although it hasn’t turned to licensing. Instead, the state’s Department of Environmental Services offers Green SnowPro training for snow removal contractors; those who take it are protected against liability to slip-and-fall claims.

“What we heard from the contractors is that it was very challenging for them to reduce given the liability concerns. One of the reasons they put down so much salt is to prevent liability in a slip-and-fall case,” says Ted Diers, administrator in the Department of Environmental Services’ water division. “What we did was we wrote a bill for our legislature that would give limited liability relief for people that have gone through our Green SnowPro training program.”

If someone slips on a parking lot full of salt drifts, it’d be tough to argue that the landowner had been negligent. But more visible salt doesn’t necessarily mean more safety — especially if temperatures are cold enough to render it ineffective (sodium chloride works only between 0 C and -7 C).

“Because putting salt down increases your safety, the assumption is that the more salt down, the more safety you’ll get — and that’s simply not true,” says Bill Thompson, manager of integrated watershed management with the Lake Simcoe Region Conservation Authority. “There’s a point beyond which putting more salt down doesn’t actually increase safety. It’s a waste of money. It’s an impact on the environment. And in some cases, it may cause pavement to become slipperier ... When you’ve got really high amounts of salt on some sidewalks you feel like you’re walking on marbles.”

The conservation authority has worked with Smart About Salt — which began as a joint initiative between Landscape Ontario and the Region of Waterloo — to train some 200 area contractors in how to reduce their use of road salt safely. Thompson says the authority is also watching the New Hampshire situation closely, to see how well the legislation works. For now, though, it’s focused on education.

A major part of the solution, says Lee Gould, executive director of Smart About Salt, is to educate people about winter safety gear and change their attitudes toward snow and ice. Snow tires and boots with good traction, for example, make slippery surfaces safer — and undercut the expectation that pavement should be visible 365 days a year.

“There needs to be a lot of things that change. There needs to be a change in attitude and culture in terms of how we view winter so we’re taking the necessary precautions — snow tires, sensible footwear,” says Gould. “I think the expectation of having bare tarmac is unfortunate.”