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 voirie.

Cet article examine la possibilité que le sel de voirie augmente la
mortalité par cancer.

Maps of:

Cancer Mortality
Rates by State
Economic Area

Possible pathways
of road salt
movement through
the environment

(photos: 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)

Is Road Salt a
Major Carcinogen?

Harold D. Foster, PhD
Professor, Department of Geography, 
University of Victoria, BC
February 2000

ince 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 damage. 
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 1985).

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 about 5 million tons of road salt annually
	Primary highway   =========
	Secondary highway   =========
	Residential street

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?