Dioxins are chemicals that are produced as a by-product of industrial and combustion activities. Dioxins are found at their highest levels in soil, sediment, and animal fatty tissues and may play a role in a variety of health effects.
See the WHO fact sheet on Dioxins
ATSDR ToxFAQs: Dioxins
Review of research concerning dioxin exposures and breast cancer from the Breast Cancer Prevention Partners.