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Great Lakes Article:

What's so bad about road salt?

Stories by Steve Buist, Science Reporter
The Hamilton Spectator
03/03/2002
HARD HABIT TO BREAK: Road salt may stop us from dying on our highways in winter, but the stuff is bad for plants and wildlife. Those dangers are competing ones and Canada hasn't yet found a way to balance them. Confused by all the hubbub over chlorides and leachate and road salt and what's floating through our sewers?

Don't worry. You should be.

At a time when water quality is front and centre in the public eye, all three levels of government are sending out conflicting messages on salt pollution.

The subject has been bubbling near the surface in Hamilton for several years as the city, Ontario's environment ministry and Philip Services Corp. sort out questions that surround leachate from the company's Taro East landfill site in upper Stoney Creek.

It recently came to light that about 30 million litres of leachate were stockpiled in the landfill, as the company sought approval to release the contaminated liquid into the municipal sewer system.

One of the main problems with the leachate is that it is high in chlorides, the electrically-charged atoms of chlorine that break away when salty material dissolves in water.

But high levels of chlorides also enter the sewers, groundwater and other bodies of water from runoff that is contaminated with road salt in the winter.

Road salt is simply sodium chloride, which readily breaks apart into sodium and chloride ions in water.

About 1.8 million tonnes of road salt are spread on Ontario roads in an average winter -- almost 40 per cent of the total used in Canada.

A Danish study in 1997 looking at road runoff found that chloride levels of samples collected in February were 1,200 times higher than in July.

More importantly, the study also showed that groundwater concentrations of chlorides were three times higher downstream than upstream even three months following the period of heaviest road salting.

It's clear that there are some important environmental questions attached to the issue of chlorides in our waterways.

Now, try to make some sense of these various stances adopted by three layers of government:

* Hamilton's sewer use bylaw limits the amount of chlorides that can be discharged into the sewer system by an individual or a company.

That's more restrictive than a model proposed four years ago by the environment ministry -- and also more restrictive than some of the surrounding municipalities.

At first glance, that sounds like a good thing.

But there are some cracks in that foundation.

For one thing, the city will allow companies to sign overstrength or compliance agreements. In exchange for cash, a company is then given the right to discharge wastewater to the sewer system that might exceed some limits in the bylaw, such as chlorides.

For another thing, the city has cleverly exempted itself from its own sewer rules.

When the bylaw was crafted in 1989, a simple one-line clause was inserted into it that allows leachate from the municipality's landfill sites to exceed its own sewer use parameters.

The Glanbrook, Ancaster and Upper Ottawa Street landfill sites are all hooked into the municipal sewer system.

What's more, the certificates of approval that set out the operating conditions for the city's sewage treatment plants contain no standards that must be met with regard to the discharge of chlorides.

It's estimated that about 150,000 tonnes of chlorides a year pass through the Woodward Avenue sewage treatment plant into Hamilton Harbour.

And the chlorides that flow through the Dundas sewage treatment plant end up in the shallow, sensitive waters of Cootes Paradise.

Compounding the problem is that water levels in Cootes Paradise can decline significantly over the summer and fall, which concentrates the pollutants in a smaller quantity of water.

* In contrast with the City of Hamilton's position on chlorides, Ontario's environment ministry has proposed a model sewer use bylaw that takes chlorides off the list of measurable standards.

It's an acknowledgement by the province that chlorides are virtually impossible to treat once they're dissolved in water.

"(But) even though there are limited treatment options, we still believe that the less chlorides that enter the ecosystem, the better it is for everyone," said John Steele, environment ministry spokesman.

Municipalities aren't obliged to adopt the proposed model, which leaves open the possibility that neighbouring municipalities discharging into the same body of water might have different standards for contaminants.

Ontario also happens to be the Canadian leader when it comes to the use of road salt, and about one-third of the 1.8 million tonnes used annually in Ontario is spread by the transportation ministry on provincial highways.

* Just to thoroughly confuse the issue, Environment Canada is about to declare road salt a toxic substance under the Canadian Environmental Protection Act.

A 60-day public comment period is just ending and barring a change of heart, road salts will make their way onto Schedule 1 of the Toxic Substances List, standing shoulder to shoulder with some of the nastiest carcinogens and pollutants around.

Environment Canada also points out that its decision has nothing to do with human health.

"There is no demonstrated link between the use of road salts and an adverse human health effect," according to a government background paper. The decision was made on the basis of environmental impacts to plants and wildlife.

Chlorides are a problem for plants and small creatures for the same reason that we can't drink salt water to quench our thirst -- basically, it causes us to become dehydrated.

The cells inside an organism are bathed in fluid that fills the tiny spaces in between. When the excessive chloride and sodium ions are taken in through the roots or absorbed by an organism, they increase the osmotic pressure between the fluid and the cells.

It's not easy for the chloride and sodium ions to cross the membrane into cells, so they float around in this extracellular fluid.

That means on one side of a cell membrane is the denser, chloride-filled liquid and on the other is less-dense water.

To equalize the pressure, water flows out of the cells since it's easier for water to flow out than for the salts to flow into the cells. In essence, the plant or organism dehydrates itself.

So most people would agree that it's an admirable decision to protect other wildlife, even if humans aren't being harmed directly.

Here's the problem. According to the very first line of the background paper:

"The Government of Canada will not ban road salts. Road safety is our top priority."

Instead, the federal government will now try to walk that fine line between protecting the environment on one side and protecting the safety of motorists on the other.

But by using the Canadian Environmental Protection Act to classify road salts as a toxic substance, it starts the clock ticking.

Once the recommendation is passed, the federal government will then have two years to develop management measures to reduce the impact of road salts on the environment.

Yale Center for Environmental Law and Policy
www.yale.edu/envirocenter

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