Exposure to Estrogen-like Industrial Chemicals. Chemicals with estrogen-like effects, called xenoestrogens, have been under suspicion for years. There has been particular concern with pesticides containing organochlorines (DDT and its metabolites, such as dieldrin) and pyrethroids (permethrin), but at this time evidence of any causal association is very weak.
Exposure to Diethylstilbestrol. Women who took diethylstilbestrol (DES) to prevent miscarriage have a slightly increased risk for breast cancer. There may also be a slightly increased risk for their daughters (commonly called “DES daughters”), who were exposed to the drug when their mothers took it during pregnancy .
Radiation Exposure.Heavy exposure to radiation is a significant risk factor for breast cancer. Girls who receive high-dose radiation therapy for cancer face an increased risk for breast cancer in adulthood. Low-dose radiation exposure before age 20 may increase the risk for women with BRCA genetic mutations.