BUFFALO, N.Y. -- A new study of the relationship of pesticides and PCBs with breast cancer shows that these compounds are not a risk factor for breast cancer for the general population of women.
Researchers at the University at Buffalo found that blood levels of organochlorines -- such as DDE, HCB, mirex and PCBs -- were not higher in women with breast cancer than in healthy women.
However, when participants were separated into groups according to history of breast-feeding, women with breast cancer who had never breast-fed had significantly higher levels of organochlorines than healthy women who never breast-fed. No difference was seen for women in either group with a history of breast feeding.
"These results suggest that higher blood levels of organochlorines were a risk factor for breast cancer only for women with no history of breast feeding," said Kirsten Moysich, Ph.D., research instructor in the UB Department of Social and Preventive Medicine and chief investigator on the study.
Previous studies by UB epidemiologists found that breast feeding, as well as having been breast-fed, appeared to offer women some protection against developing breast cancer later in life. These studies did not measure levels of organochlorines.
"These chemicals are stored in fatty tissue, including breast tissue," Moysich said. "The chief mechanism for eliminating them from breast tissue is lactation, which flushes them from the system." She said that even though the baby is exposed to these substances, the beneficial effects of breast feeding appear to outweigh potential risks associated with these organochlorines.
Results of the study will be presented at the International Society for Environmental Epidemiology in Taiwan on Aug. 20.
The research involved 154 postmenopausal women with breast cancer and 192 healthy women of similar age selected randomly from the general population. Extensive information on diet, reproductive and medical history and other lifestyle information was obtained from all participants through personal interviews.
Researchers also drew blood samples and measured levels of DDE, HCB, mirex and PCBs. Organochlorine pesticides and PCBs, or polychlorinated biphenyls, were used widely in the U.S. until the 1970s, when they were banned from commercial production due to concerns about potential harmful health effects.
Since these compounds are stored in body fat and are not easily broken down, they accumulate in the body over time. Some of these chemicals have been shown to increase estrogen activity in animals and consequently have been linked to breast-cancer risk.
Moysich said the study results suggest that environmental exposure to organochlorines is related to the risk of breast cancer only in postmenopausal women who have never breast-fed, and is not a risk factor for breast cancer for the population at large.
"It is tempting to blame environmental exposure to potential carcinogens for causing breast cancer, because there is little to be done about it," said Moysich. "It eliminates the responsibility for changing one's lifestyle or habits. But our study and others don't show an adverse effect for the general population."
Also participating in the study were Christine Ambrosone, Ph.D.; John Vena, Ph.D.; James Marshall, Ph.D.; Saxon Graham, Ph.D.; Rosemary Laughlin, Ph.D.; Pauline Mendola, Ph.D., and Jo Freudenheim, Ph.D., all current or former faculty members in the UB Department of Social and Preventive Medicine. Also, Enrique Schisterman, doctoral candidate in the department; Peter Shields, M.D., of the National Cancer Institute, and Paul Kostyniak, Ph.D., of the UB Toxicology Research Center.