Nutrition Action Healthletter
March 1999 — U.S. Edition

Pesticides and Breast Cancer

Women with higher levels of the pesticide dieldrin in their blood have a greater risk of breast cancer, say researchers from the Centers for Disease Control and Prevention in Atlanta and elsewhere.
   In 1976, John Brock and colleagues collected blood samples from 7,712 healthy Danish women in the Copenhagen City Heart Study. By 1993, 240 of the women had been diagnosed with invasive breast cancer. The researchers compared the levels of 18 pesticides (or their breakdown products) and the chemical contaminant PCB in blood samples from those women to samples from 477 similar women in the study who had not been diagnosed with breast cancer.
   Women with higher blood levels of dieldrin were twice as likely to have breast cancer than women with lower levels. There were no links between cancer and PCBs or DDT, DDE, or any other pesticide.
   “We need to do more sensitive analyses of dieldrin levels in studies in the U.S., where blood levels are lower than in Denmark,” says Brock. Dieldrin was used on apples and other food crops until the late 1970s, and for termite control until 1985, he adds. —Bonnie Liebman

Lancet 352: 1816, 1998.
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