This fact sheet describes the scientific evidence of whether polycyclic aromatic hydrocarbons (also called PAHs) affect the risk of breast cancer and other cancers. PAHs include over 200 chemicals. This fact sheet includes information on how PAHs are formed and where they are found, a summary of studies that have evaluated their cancer risk, how humans can be exposed from PAHs found in the air, food, water, and skin contact, how to reduce exposure, how PAHs are regulated, and future research needs.