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See also   Intro and ’What Causes Cancer?’   or   Wendy’s personal Battle with Cancer

Is cancer in our blood? 
Broadcast: March 5, 2006

Wendy Mesley reading her blood test results.

The Canadian Cancer Society says healthy lifestyle choices could prevent 50 per cent of cancers. They say a "small percentage" of cancers are linked to environmental toxins, or carcinogens.

"I had my blood tested; the results show I’m full of carcinogens," says Marketplace host Wendy Mesley, who had breast cancer.

Each of us likely has pollutants in our blood. A recent study analyzing the blood and urine of a small group of Canadians found varying levels of contamination from heavy metals, pesticides and other toxic chemicals (such as PCBs, mercury, lead). A similar study of 500 Canadians found the same results.

The contaminants included known and suspected carcinogens and other chemicals that may cause reproductive disorders, harm the development of children, disrupt hormone systems or are associated with respiratory illnesses.


In Canada, about 14 million kilograms of carcinogens are released into the environment every year.

What’s not clear is at what level a chemical becomes toxic to people. Scientists around the world have been working to understand at what point a toxin in our blood becomes a health risk, but the matter remains one of intense debate.

Nonetheless, the fact that we carry contaminants with us in our blood is a sobering one. Common sense tells us that we are what we eat, what we breathe and what we expose our bodies to in our day-to-day lives. For most of us, that includes a lifetime exposure to industrial chemicals, pollutants and pesticides.

"I don’t think tha my blood tests will uncover the reason that I got cancer. I don’t think that it’s that simple," says Mesley. "But I have been accumulating toxins, probably since I was born - maybe even before. And the levels of these keep going up. At some point, we should start to do something about them. Maybe that time is now."

What’s in Wendy’s blood


A carcinogen is a chemical known or believed to cause cancer in humans. The number of proven carcinogens is comparatively small, but many more chemicals are suspected to be carcinogenic.Wendy Mesley’s blood was tested for some 60 heavy metals, pesticides and other toxic chemicals.

Among the pollutants found within her blood were several known or suspected carcinogens, including:

Polychlorinated biphenyls (PCBs)

Recognized as carcinogens by California’s Proposition 65, PCBs are a group of chemicals that contain 209 individual compounds (known as congeners) with varying harmful effects. PCBs are no longer produced or used in North America; the major source of exposure to PCBs today is the redistribution of PCBs already present in soil and water. PCBs bio-accumulate in the fat of humans and animals, including fish. They are ranked as one of the most hazardous compounds to ecosystems and human health.

Organochlorine pesticides

Classified by California’s Proposition 65 as suspected carcinogens, organochlorine pesticides are man-made organic chemicals. DDT was the first that was used on a large scale in North America. Although most organochlorine pesticides are no longer used in Canada, many are manufactured in North America for use elsewhere, especially in developing countries. Research has found that many organochlorine pesticides are extremely persistent in the environment and in people’s bodies.


Listed by the U.S. Environmental Protection Agency as a possible human carcinogen, and by California’s Proposition 65 as a recognized carcinogen, cadmium has been shown to be a developmental toxicant in animals, resulting in fetal malformations and other effects, but no conclusive evidence exists in humans. The main sources of cadmium in the air are the burning of fossil fuels such as coal or oil and the incineration of municipal waste. An association between cadmium exposure and an increased risk of lung cancer has been reported from human studies, but these studies are inconclusive due to confounding factors. Animal studies have demonstrated an increase in lung cancer from long-term inhalation exposure to cadmium.


Recognized as a carcinogen by California’s Proposition 65, nickel is also ranked as one of the most hazardous compounds to human health. Nickel is a metal found in natural deposits as ores containing other elements. The greatest use of nickel is in making stainless steel and other alloys. Fuel oil combustion leads to releases of nickel to the atmosphere. Other sources include emissions from mining and refining operations, municipal waste incineration, and windblown dust. Sources of nickel in water and soil include storm water runoff, soil contaminated with municipal sewage sludge, wastewater from municipal sewage treatment plants, and groundwater near landfill sites.