Environmental pollutants increase cancer risk

July 15, 2005 - Ever since U.S. President Richard Nixon declared war on cancer, hundreds of billions of dollars have been spent battling this dread disease. We routinely hear about "breakthroughs" in cancer treatment as biotech companies tout their newest products. Yet this year, for the first time, cancer has surpassed heart disease as our number one killer.

On a recent CBC radio program, cancer experts pointed out the disease is related to old age, so as the proportion of older people increases in the population, cancer rates will climb. But while progress has been made in detecting, treating and prolonging the life of cancer patients, overall the experts concluded that we are still losing the war.

So what else is going on? I used to take my daughters fishing off the jetty near our house until one day we noticed lumps at the base of the fins of one of the flounders. We took it home to cut open the lumps, expecting to find parasites. Instead, we found they were tumours. Recently at a talk I gave in Toronto, a veterinarian told me that when she started her practice 20 years ago, she'd see pets with cancer once or twice a month. Now, she says, she sees one or two a day!

Humans are incredibly inventive creatures and over the past hundred years, technological innovation has transformed the planet. In 1962 when Rachel Carson published Silent Spring about the unexpected effects of pesticides, she pushed the environment into public consciousness and was attacked outrageously by the chemical industry. Today, more pesticides are applied worldwide than when Carson issued her warning.

In fact, we have altered the chemical makeup of the biosphere to such an extent that we cannot escape the toxic debris of industrial activity. Scientific monitoring stations in Antarctica detect pollutants spread on the winds and in water vapour from all parts of the planet. Volatile compounds sprayed on fields in the southern U.S. or Russia evaporate into the atmosphere, circle the globe, precipitate over glaciers or ice sheets and end up concentrated in lake trout caught in Banff and Jasper.

More than 70,000 human-created compounds, most never tested for toxicity or carcinogenicity, are now in use. But these chemicals don't just disappear. From the moment of our birth to the last breath we take before death, we suck air deep into our bodies and filter whatever is in it. More than 60 per cent of our body weight is water which must be constantly replenished. Most of our food is grown in soil, the same soil in which we dump our wastes. We even spray the plants and animals we eat with poisons. Is it any wonder why all our bodies now contain trace amounts of these chemicals?

It takes an enormous effort to pinpoint a deleterious compound. It took years before thalidomide was tracked down as the cause of limb malformations and DES as the cause of reproductive cancers in daughters of women treated with it during pregnancy. Tests must be carried out on a scale large enough to yield numbers that are statistically significant and each compound must be studied under different conditions and concentrations.

Such studies are also normally done in isolation. But this is not how these chemicals are used in the real world, where they can combine with dozens of other compounds. A report published earlier this year in the journal Environmental Health Perspectives, for example, found that the common pesticide Roundup was more than twice as toxic as glyphosate alone, its only supposed "active" ingredient. The pesticide mixture was also linked to potential reproductive problems -- something else not attributed to glyphosate alone.

Scientists are reluctant to suggest that a polluted world may be an important factor in the epidemic of cancer afflicting us today. But common sense should tell us that many of these compounds have powerful biological effects. If we stop using the biosphere as a toxic dump, we might actually make better progress in the war against cancer.