Environmental chemicals and breast cancer: A review of epidemiologic studies from 2006-2013

Breast cancer is the most common cancer in women worldwide. Incidence rates are increasing globally, and most rapidly in developing countries in the Middle East, central Latin America, and south and southeast Asia. Mortality is also rising in these countries and disproportionately affecting young, pre-menopausal women whose cancers are less responsive to treatment. Poor access to care adds to this disproportionate mortality. These global patterns signal the crucial importance of prevention. To evaluate the possible role of environmental chemicals, which may be avoidable causes of breast cancer, we conducted a systematic search in PubMed with 106 search terms for articles published in 2006-2013. Eighty-nine articles reported on environmental chemicals and breast cancer. Studies included women in 31 different countries, mostly from developed regions, though the extension of studies into less developed regions is a reflection of the rising incidence of the disease on a global scale. Brody et al conducted a similar review from 2000-2006. Since then, the strength of evidence of polychlorinated biphenyls (PCBs) and breast cancer risk has grown, specifically showing that postpartum levels increase risk of breast cancer in younger women. Organophosphate pesticide exposures remain a large focus. Although results are inconsistent across studies, early life exposure to DDT increased breast cancer risk in one study. Occupational studies highlight job histories, such as health care, agriculture, and automotive manufacturing and mechanic work that show increased risk across multiple studies. Research on ambient air pollution from vehicles and industry was uniformly associated with breast cancer risk. Exposures to newer chemicals of interest, including phthalates and perfluorinated compounds were evaluated in few studies. An increasing number of women and their families are affected by breast cancer across the globe. This review underscores the importance of identifying environmental risk factors to prevent the disease's upward trend in incidence and mortality.