so bad about road salt?
Stories by Steve Buist, Science Reporter
The Hamilton Spectator
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
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
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
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
* 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
"(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
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
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
That means on one side of a cell membrane is the denser,
chloride-filled liquid and on the other is less-dense
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
So most people would agree that it's an admirable decision
to protect other wildlife, even if humans aren't being
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