Peace and Environment News* December 1995-January 1996
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Peace and Environment News * December 1995-January 1996 |
by Hans Posthuma
It's a link that was underexplored for a long time—the connection between a contaminated environment and breast cancer. In recent years, however, research efforts that had focused primarily on personal factors such as heredity, diet, medical history or lifestyle have begun to examine environmental factors as possible causes of breast and other cancers.
The causes of 70 percent of breast cancer cases are unknown, and could be linked to environmental factors. So far, only about 30 percent have been identified as being related to genetic, medical or lifestyle factors.
While a direct connection between a contaminated environment and cancer has long been assumed, the research community has been slow to change its focus. As a case in point, the adverse effects of chemicals such as DDT on wildlife were known fifty years ago, yet little research was done to find any connections to cancer in people.
In the meantime, it is currently expected that one in eight North American women will contract breast cancer, a steady rise from the one in twenty rate in 1950. Canada has the second highest incidence of the disease, after the United States, with about 5,000 Canadian women a year dying from breast cancer.
Research structure to blame
Critics say the structure of research funding has been partly to blame. Money distribution is based on a peer review system, under which decisions are made by a small group of researchers, physicians and scientists. Even a House of Commons report criticized the system, saying that many important links to breast cancer remained unexplored in the past because researchers with innovative proposals tended to be excluded from funding.
The problem is not unique to Canada. In the United States, it wasn't until last year that the National Cancer Advisory Board said publicly that industrial chemicals, environmental chemicals that mimic hormones, and pesticides ought to be investigated as causes of cancer. That reversed a previous opinion that chemicals were too small a factor to be worth investigating.
Thanks in part to demands from individuals and groups such as the Breast Cancer Action Group for a more focused approach to research, the pendulum has begun to swing the other way. More funding has been allocated to breast cancer research, survivors of breast cancer are requesting more say in decision making, and there is a stronger focus on prevention.
Those who are working to change the focus of research hope that by scientifically demonstrating that certain environmental factors cause cancer, the door will be opened to preventing countless cases of cancer from happening in the first place.
Organochlorines a major culprit
A group of chemicals called organochlorines are getting the most scrutiny in recent studies. These compounds, not found in nature and almost invariably toxic either during production or in their final form, began to be produced in the early 1900s. They include PCBs, DDT, Agent Orange, dioxin and thousands of lesser-known products.
Not surprisingly, the widespread use of these chemicals since World War II and the subsequent contamination of the environment also coincided with a worldwide rise in breast cancer rates.
Some studies have already been done, finding elevated levels of DDE (the major metabolite of DDT) and PCBs to be risk factors for breast and other cancers. Predictably, other studies have concluded that the links are not "statistically significant."
Some of the evidence supporting the link comes from Israel, where breast cancer rates defied the world trend and dropped by 8 percent in the decade following the beginning of a pesticide phase-out program. From 1951 to 1976, Israel had some of the highest levels of organochlorine pesticides in the world, found in cow's milk, human milk and human tissue.
Another study, done by the York Department of Health, found that women living in Nassau County within 1 kilometre of a chemical, petroleum, rubber or plastics facility were 60 percent more susceptible to postmenopausal breast cancer than women living in other parts of the county.
Epidemiologist Mary Wolff, working at New York's Mount Sinai Medical Centre, found a fourfold increase in the amount of DDE in women with breast cancer.
Despite some studies that appear inconclusive, researchers expect to continue finding a cause and effect relationship between various environmental factors and breast cancer.
The hormone connection
Organochlorines launch a two-pronged attack on the body. First, they tend to concentrate in fatty tissue. This makes the breast, composed mainly of fatty tissue, particularly vulnerable.
Some compounds then also interfere with the body's biochemistry, mimicking the chemical behaviour of hormones or enzymes. In doing this, they fool the body into increasing production of estrogen. An excessive exposure to estrogen during a woman's lifetime has already been shown to increase the risk of breast cancer.
Chlorine ban would help
The common ingredient in all organochlorines is chlorine gas. Although it is harmless as the naturally occurring chloride ion, elemental chlorine gas is reactive, dangerous, and does not occur naturally. In addition to industrial chemicals, chlorine is used to make PVC (vinyl), disinfect drinking water, bleach paper, clean clothes and a host of other things.
Many people favour placing a "guilty until proven innocent" label on chlorine. Groups like Greenpeace and other grassroots environmental organizations support a complete ban on chlorine, partly as a result of pollution problems in the Great Lakes.
A few years ago advocates banning chlorine received support from a prestigious quarter: the Canadian-U.S. International Joint Commission. Despite pressure from industry, the government-appointed members of the commission joined the call for a ban on chlorine, saying that industry should prove any new chemicals are safe before they are put into use.
Other factors
Dangerous as they are, organochlorines are not the only environmental factors suspected of influencing the development of breast and other cancers. Other things that have moved up higher on the research priority list include various types of radiation, electromagnetic fields, exhaust emissions and more.
Even poverty is on the list, which may herald a more holistic approach to solving the problem. People with lower incomes are more at risk for many cancers, more likely to be diagnosed late, and have lower survival rates.
Hans Posthuma is a freelance writer and editor living in Kenmore, Ontario.
Converted March 21, 2000 - Lg
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