THE NEW YORK TIMES April 20, 1994
by Jane E. Brody
A new carefully designed study, the largest of its kind to date, has found no evidence that breast cancer is caused by pesticide residues that accumulate in body fat. The new finding, published in today's issue of The Journal of the National Cancer Institute, comes amid a heated debate about the possible role of environmental contaminants in causing breast cancer.
A recent report fro the New York State Health Department found that women who had lived on Long Island in the vicinity of chemical plants were more likely than others to develop breast cancer after menopause. This report, which has not yet been reviewed by other experts, did not establish a cause-and-effect relationship between chemical pollution and cancer.
The new finding contradicts the results of a smaller study published in the same journal last year. The earlier study showed a link between a woman's risk of developing breast cancer and the presence of higher than average blood levels of DDE, a breakdown product of the long-banned pesticide DDT. The new study, directed by Dr. Nancy Krieger of the Kaiser Foundation Research Institute in Oakland, Calif., found no mean increase in DDE levels in those who developed breast cancer, and did not find evidence of a link between the level of PCB's in blood and a woman's chances of developing breast cancer.
The issue of chemicals and breast cancer is a poignant one for several reasons. Many chemical pollutants, some of which are carcinogens, are present in breast milk and in the fatty tissues of the breast. Apart from weight loss, only through breast feeding are chemicals like DDT and PCB's lost from the body.
As the environment has become increasingly polluted, breast cancer rates have been rising. With medical scientists unable to explain the origins of a vast majority of breast cancers, many women and advocacy organizations have pointed a finger at noxious agents in the environment.
The Kaiser study was based on a group of 57,000 women examined in the mid- to late-1960's and then followed for more than two decades. When the study began, blood samples were taken from all participants and stored frozen.
Fro the analysis, 150 women who later developed breast cancer were matched with a comparable group of healthy women—whites, blacks and Asians—to serve as controls. When known risk factors for breast cancer were taken into account, the research reported no clear relationship was found between the amount of pesticide contamination and breast cancer rates. The blacks and Asians generally had higher levels of DDE in their blood than the white women. But the incidence of breast cancer was highest among the white women and lowest among the Asians.
In an editorial accompanying the journal report, Dr. Brian MacMahon of the Harvard School of Public Heath said that one strength of the new study was the fact that blood samples were taken years before breast cancer was diagnosed in the women and before DDT and PCB's wee banned. He wrote that while further research into this question was needed, "for the moment, we must conclude that the available epidemiological evidence over all is not supportive of an association between exposure to DDT and increased risk of breast cancer."