Known environmental carcinogens
The cancer trigger
Exposure to environmental contaminants causes many different types of cancer, contributing to as many as 10,000 deaths and 24,000 new cases of cancer in Canada each year.
The WHO's International Agency for Cancer Research has identified about 400 agents known to be carcinogenic or potentially carcinogenic to humans. Some of the known environmental carcinogens include asbestos, radon, arsenic, fine particles, polycyclic aromatic hydrocarbons (PAHs), benzene, formaldehyde, solvents, some paints and dyes, dioxins, PCBs and pesticides. Many studies have linked specific contaminants to particular types of cancer.
The Canadian Cancer Society and Cancer Care Ontario reported in 2005 that water disinfection byproducts had been linked to bladder cancer; pesticides to non-Hodgkin's lymphoma; fine particles and PAHs in diesel exhaust to lung cancer; arsenic to lung, skin and bladder cancers; and extremely low-frequency electromagnetic fields to childhood leukemia.
What scientists don't know for sure is how safe long-term exposure to supposedly "low" levels of toxic chemicals is. We don't know the dangers of wearing clothes treated with carcinogenic brominated flame retardants, applying cosmetics that contain formaldehyde or eating poultry that contains trace levels of arsenic that was added to chicken feed, all substances flagged by the WHO but still widely available.
Better safe than sorry
As a society and as individuals, the best way to prevent cancers relating to environmental exposures is to err on the side of caution, even when cause-and-effect relationships have not been proven conclusively. For example, regulators should take steps to reduce exposure to probable carcinogens such as diesel emissions, says Ray Copes, medical director of environmental health services at the B.C. Centre for Disease Control in Vancouver. Diesel exhaust from trucks, buses and construction equipment, Copes points out, is a major source of fine particle pollution, PAHs and benzene.
But you can also take steps as an individual. Know what consumer products may have carcinogenic properties and avoid or limit your exposure to them; for example, certain air fresheners contain potentially carcinogenic benzene compounds. And the Canadian Cancer Society advises that heating cookware with nonstick coatings at high temperatures can create fumes that contain a suspected cancer-causing chemical tetrafluoroethene.
Use environmentally friendly cleaning products that don't release volatile organic compounds. Avoid using pesticides on your lawn or garden. Prepare food to minimize ingestion of toxic chemical residues. For example, "You can reduce your exposure to dioxins and PCBs by preparing meat so that fat drains away," says Copes. "People have more control than they realize over their personal environment. If you spray the area around your head with an aerosol, that source may be more important than a large smokestack five kilometres away."
It's worth noting that Canadians are more inhibited in making good choices than Europeans are, because we are not being fully informed about carcinogens in consumer products. In the European Union, as well as in California, community right-to-know legislation requires manufacturers to list carcinogens on product labels.
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