Last week, scientists unveiled a report that named more than 200 chemicals that appear to cause mammary gland tumors in animals. Among them: ingredients in mace sprays used to ward off attackers, compounds released from cooking with canola oil, pesticides, industrial solvents and many other commonly encountered chemicals.
But this does not mean women should stop cooking with canola or cower indoors for fear of getting breast cancer, experts say. Although some scientists would like to see levels of many of the listed contaminants reduced in the environment, the list is more of a starting point for researchers to investigate further.
Two years ago, the Susan G. Komen Breast Cancer Foundation, which funds research into causes of breast cancer, asked the Silent Spring Institute in Newton, Mass., to compile a database on all the available evidence that chemicals found in the environment cause mammary tumors in animals.
Scientists at the institute (which is an organization investigating environmental effects on women's health) combed through five databases that keep track of cancer studies. Any chemical that showed an increase in mammary tumors in at least one animal study was included as a chemical of interest. In all, the scientists found 216.
"The authors identified interesting compounds that need to be studied further. Are they ready for prime time and regulation? I don't think so. But people should study them," says breast cancer researcher Michael Gould of the University of Wisconsin- Madison.
In the database, the authors reported how carcinogenic the chemical had been classified by two organizations: the International Agency for Research on Cancer and the U.S. Environmental Protection Agency. These classifications were based on all cancers, not just breast cancer. They also noted the strength of the studies.
"If we could see the evidence was weak, we put that in the summary," says lead author Ruthann Rudel, a toxicologist at the Silent Spring Institute. "We didn't want to exclude studies because then we would have had to come up with criteria for how strong the evidence was."
Two other databases also were compiled by researchers from a variety of institutions. One looked at which environmental contaminants contribute to breast cancer in people. The best evidence ranked the persistent environmental contaminants PCBs (polychlorinated biphenyls) and car exhaust PAHs (polycyclic aromatic hydrocarbons) at the top of the list.
