State of the evidence: the connection between breast cancer and the environment.

A substantial body of scientific evidence indicates that exposures to common chemicals and radiation, alone and in combination, are contributing to the increase in breast cancer incidence observed over the past several decades. Key recurring themes in the growing scientific literature on breast cancer and environmental risk factors are: (a) the importance of understanding the effects of mixtures and interactions between various chemicals, radiation and other risk factors for the disease; and (b) the increasing evidence that timing of exposures matters, with exposures during early periods of development being particularly critical to later risk of developing breast cancer. A review of the scientific literature shows several classes of environmental factors have been implicated in an increased risk for breast cancer, including hormones and endocrine-disrupting compounds, organic chemicals and by-products of industrial and vehicular combustion, and both ionizing and non-ionizing radiation.