A new report on the causes of breast cancer concludes exposure to environmental toxins and radiation contributes more than previously understood to the risk of developing breast cancer.
The report, to be released today by San Francisco-based Breast Cancer Fund and Breast Cancer Action, reviews a year's worth of scientific work on the disease. That work, the report found, increasingly points to common chemicals found in the home -- in plastic food containers, rainwear, pesticides, paints and varnishes -- as an important factor in a person's breast cancer risk.
"We can't say breast cancer is all women's fault," said Nancy Evans, an author of the report and a health science consultant for the Breast Cancer Fund. "There's very little testing going on of the chemicals out there. And there's no testing prior to market of the effects that these chemicals will have when they get into the environment."
Though overall cancer rates are down, the incidence rate for many cancers -- including breast cancer -- are up. A generation ago, the lifetime risk for someone developing cancer was one in four. Today one out of three women will develop some kind of cancer. For men, the odds are one in two.
About half of all breast cancers in women can be attributed to some cause: genetic predisposition, a decision to have children or not, the age at which she gave birth and whether those children were breast fed.
The rest remain mysteries -- until environmental causes are taken into account, according to the report, "State of the Evidence 2004: What is the Connection Between the Environment and Breast Cancer?"
Surveying 21 research studies published since February 2003, the report found chlorinated chemicals, found in drinking water and many manufacturing processes, such as paper production, were associated with higher cancer rates in three studies.
Another study found the hormone Zeranol, used to fatten beef cattle, contributes to the proliferation of breast cancer cells -- even at hormone levels below that which the U.S. Food and Drug Administration considers safe.
And, in what Evans called one of the more surprising findings, researchers at Duke University identified a new class of chemicals, dubbed "hormone sensitizers" -- that make cells more responsive to hormones like estrogen.
Estrogen helps breast cancer cells proliferate, which is why delayed pregnancy or no pregnancy is a risk factor in women -- the more a woman ovulates, the longer the period of exposure to unopposed estrogen.
These hormone sensitizers, particularly the solvent ethylene glycol methyl ether used in paints, varnishes, dyes and fuel additives, essentially sensitizes cells to estrogen.
"When you're exposed to a chemical that makes cells more responsible to estrogen -- both your own estrogen and the estrogen in an oral contraceptive -- that makes them proliferate more," Evans said. "When they proliferate more, they have more of a chance of But with many variables contributing to the risk of breast cancer, other researchers expressed caution before blaming drinking water or Tupperware.
Dr. Robert Hiatt, a professor of epidemiology at the University of California, San Francisco and leader of a ground-breaking, seven-year study examining the effects of the environment on one aspect of breast cancer, suspects there are environmental influences controlling, for instance, the onset of puberty -- a key breast cancer factor.
But those influences include diet and physical activity in addition to environmental toxins. Separating their various influences requires further work, said Hiatt, who is working with Evans and the Breast Cancer Fund on this front..
"There's no smoking gun," he added. At the same time, "it's not like we're in a hopeless situation where things are spiraling out of control.... A lot of stuff in the environment is getting into our systems and it's measurable. How much of this has a biological effect and a harm is another question."
Likewise, scientists at the Centers for Disease Control and Prevention have long warned against equating health risks to low-level exposure to a particular compound. That was the message Wednesday from the American Chemistry Council, representing manufacturers of 90 percent of the country's chemical products.
"Government and independent research into the causes of breast cancer have generally pointed to diet and lifestyle, not the low levels of modern substances that are present in the environment," said council spokesman Chris VandenHeuvel.
"People are living longer and healthier lives in part due to the many essential and life-saving products of modern chemistry."
Written by: Douglas Fischer
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