Pesticides Might Not Lead to Breast Cancer

Contrary to previous beliefs in the scientific community, major environmental pollutants such as DDT and PCB may not lead to breast cancer, according to a recent study published in this week's New England Journal of Medicine.

The study, led by Associate Professor of Epidemiology at Harvard School of Public Health David J. Hunter, reports findings which do not correlate with earlier beliefs that breast cancer was directly related to blood DDE, the metabolized from of DDT and PCB levels.

DDT and PCB, chemicals that were commonly used as pesticides, had been banned in the United States by the late 70s. The chemicals posed a risk because they are fat soluble and accumulate in the body over time without being metabolized.

The article titled "Plasma Organochlorine Levels and the Risk of Breast Cancer," is the largest study in this field to date.

Hunter obtained blood samples from 32,826 women in 1989. Three years later, a follow-up study was conducted, and 240 of those women were diagnosed with breast cancer. Their blood samples were then matched with those of the control women with the corresponding ages.

The data showed a lower median concentration of DDE (4.71 parts per billion) and PCB (4.49 parts per billion) in the serum of cancer patients than in the controls (5.35 and 4.68 parts per billion respectively).

Hunter said that the difference was not significant enough to indicate that the chemicals were negatively related to developing breast cancer.

But many previous researchers with smaller numbers of cases had found there to be a higher DDE level in cancer patients. Hunter said that many small scale researchers were more subjected to random fluctuations and had "irreproducible results" in the past.

Hunter said that the data of two other large studies--one conducted in North California with 150 cases and the other in Europe--both agreed with his conclusion that there is no correlation between plasma chemical level and the risk of breast cancer.

He added that the research conducted in California was analyzed in the same laboratory--belonging to Mary Wolff, researcher at Mt. Sinai school of Medicine at New York City--using gas chromatography.

"We suspect that exposure to environmental pollutant is accounting for a small proportion, if any, of breast cancer, and we need to turn our attention to other potential causes," Hunter said.

Hunter's study included 68 percent post-menopausal women, which he said is a higher-risk group.

"The risk factors for post or pre-menopausal women are different," he said.

He said that the next step in the study would be to focus on the effects on women who are exposed to the chemicals as children or adolescents.

The project is a part of the Nurses' Health Study--headed by Dr. Frank E. Speizer, Kass professor of medicine at Harvard Medical School--and has been going on for more than 20 years to study various women's diseases.