Environmental estrogens and breast cancer risk.

Controversy exists over the role that environmental estrogens, such as pesticides or polychlorinated biphenyls (PCBs), might play as risk factors for breast cancer. Several laboratory studies have suggested that these chemicals function as weak estrogens, binding to the estrogen receptor and inducing various measures of estrogen response. However, epidemiologic studies assessing the link between exposure to pesticides or PCBs and breast cancer have generally not shown enhanced breast cancer risk with higher levels of xenoestrogen exposure. These findings heighten our uncertainty about the relevance of the preclinical findings to human breast cancer risk.