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Study: Pesticides Raise Breast Cancer Risk by Increasing Bad Estrogen

October 3, 1994 GMT

NEW YORK (AP) _ Researchers trying to explain the disturbing link between pesticides and breast cancer have discovered that pesticides appear to raise levels of a harmful form of estrogen.

The finding came as a surprise to the director of the research, who undertook the study expecting to show that pesticides had no effect on estrogen.

″I was wrong,″ said H. Leon Bradlow, a biochemist with the Strang Cancer Prevention Center at Cornell University Medical School. The study showed that after exposure to pesticides, ″your risk ratio is greater than what it was before,″ Bradlow said in an interview Monday.


Several earlier studies have linked pesticides to an increased risk of breast cancer, though one study failed to find a link. The new study adds to the evidence by showing how pesticides may be exerting a harmful effect, Bradlow said.

Penelope Fenner-Crisp, a pharmacologist and pesticide specialist with the Environmental Protection Agency, said the EPA is taking the link between pesticides and hormones very seriously. That includes more than simply encouraging further research, she said.

″We should also think about how we might go about encouraging exposure reduction,″ she said. ″I don’t think we want to sit around five or 10 years while the research goes on, and then think about reducing exposure.″

The study will be published soon in Environmental Health Perspectives, a journal of the National Institute of Environmental Health Sciences.

The study builds on Bradlow’s previous research showing that there is a ″good estrogen″ that protects against breast cancer and a ″bad estrogen″ that is associated with increased risk of the disease.

The distinction is analogous to the one made between good and bad cholesterol with respect to heart disease, said one of Bradlow’s collaborators, Devra Lee Davis, an epidemiologist with the Health and Human Services Department.

The new study ″strengthens the case that some portion of breast cancer may be avoidable and due to factors we can control,″ Davis said. Those factors include pesticides containing chlorine, along with some plastics and fuels and a few natural products, she said.

The researchers exposed human breast cells in the test tube to DDT and other chlorine-containing pesticides. They found that the pesticides’ effect on bad estrogen was three to four times as great as that of a known human carcinogen that was used as a comparison.


In a separate study, Bradlow and his colleagues found that woman who eat ″cruciferous″ vegetables - broccoli, cauliflower, brussels sprouts and cabbage - appear to counteract the harmful effects of pesticides.

″We can’t prove it’s going to work, but we can suggest a plausible thing that isn’t going to hurt them and could help them,″ Bradlow said.

A anti-cancer substance found in these vegetables called indole-3-carbinol was found to increase the ratio of good estrogen to bad estrogen, Bradlow said.

He said that a woman who eats such vegetables regularly could significantly reduce her risk of breast cancer, although he cannot yet say precisely how much lower the risk would be.