Est-ce que le sel de voirie est une importante substance cancérogène?
Les Canadien(ne)s répandent aussi environ 5 millions de tonnes de sel de
Cet article examine la possibilité que le sel de voirie augmente la
mortalité par cancer.
Rates by State
of road salt
Committee on the Comparative Costs of Rock Salt and Calcium Magnesium
Acetate (CMA) for Highway Deicing 1991.
Special Report 235. "Highway Deicing", Trans- port Research
Board, National Research Council, Washington, DC)
Harold D. Foster, PhD
Professor, Department of Geography,
University of Victoria, BC
1970, highway agencies in the United States have applied about 10
million tons of road salt each winter. Canadians also put down some 5
million tons annually. Sodium chloride is by far the most popular of the
de-icers since it is inexpensive, reliable and easy to store and apply.
Nevertheless, it causes enormous infrastructural and environmental
To illustrate, its use is reducing water quality in many
aquifers and lakes, killing roadside vegetation and wildlife and
damaging soils, road surfaces, bridges, parking garages and automobiles.
In the United States, it has been estimated that the annual road salt
cost for motor vehicle and infrastructural damage is between $3.5 to $7
billion. These estimates do not include the costs of environmental
damage to soil, vegetation or surface and groundwater.
Acid Rain - pH
Corrosivity of the environment by region
(Turcotte and Baboian
There may, however, be an even more dangerous consequence of adding
road salt to highways. In 1986, this author explored correlations
between USA mortality from 66 cancers and groups of cancers and 219
environmental variables. In "Reducing Cancer Mortality: A
Geographical Perspective", we argued that these correlations were
suggestive of potential protective effects by soil selenium and calcium
and demonstrated elevated cancer mortality in states where soils
contained high levels of mercury or where road salt was widely used.
Subsequent clinical and/or field trials appear to have proved beyond
reasonable doubt that selenium and calcium are protective against a wide
variety of cancers. Mercury is a selenium antagonist, reacting with it
to form insoluble mercury selenide that does not pass into the food
chain. If, as the evidence strongly suggests, selenium is protective
against cancer, mercury must promote it. This leaves road salt as the
only potential major environmental carcinogen identified by this author
for which the evidence is still inconclusive. Nevertheless, the
geographical data and analyses currently available suggests that road
salt may be associated with elevated mortality from cancers of the
breast, lung, esophagus, throat, larynx, large intestine, rectum and
bladder. It is impossible to apply the Bradford-Hill criteria to these
apparent associations since, despite the fact it is so widely used,
there is virtually no available literature on the health impacts of road
salt. Cause and effect relationships, therefore, cannot be established
without further study.
Canadians put down
5 million tons of road salt annually
How likely is it that road salt use increases cancer mortality?
Environment Canada has evaluated the toxicity of a wide variety of
sources of storm water and has established that the most damaging is
run-off from de-iced, multi-lane divided highways with traffic densities
over 100,000 vehicles per day. This is thought to be due to the quick
contaminant release during snowmelt, the enhanced mobility of heavy
metals caused by road salt and the presence of elevated concentrations
of this de-icing agent itself. Most road salt contains sodium
ferrocyanide as an anti-caking and corrosion inhibitor. Under acidic
conditions, in the presence of strong sunlight, this compound is known
to break down, generating toxic cyanide forms, including hydrogen
cyanide. These toxins appear to have caused serious fish kills as the
result of sodium ferrocyanide’s use by the BC Ministry of Forests in
fire retardants. Recent animal studies also have shown chronic cyanide
exposure may be deleterious to liver and kidney functions and causes
both time- and dose-dependent DNA fragmentation, accompanied by
cytotoxicity. Hydrogen cyanide in cigarette smoke also is known to be
cilia toxic, and may act as a pacemaker for the action of some
carcinogens, such as aromatic hydrocarbons.
Are you sure you want to inhale wind-blown road salt or drink water
polluted by it?