Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of organic polyhalogenated compounds that are significant environmental pollutants. They are commonly but inaccurately referred to as dioxins for simplicity, because every PCDD molecule contains a dioxin skeletal structure as the central ring. This gives the molecule a dibenzo-p-dioxin ring system. Members of the PCDD family bioaccumulate in humans and wildlife because of their lipophilic properties, and may cause developmental disturbances and cancer.
Dioxins occur as by-products in the manufacture of some organochlorines, in the incineration of chlorine-containing substances such as PVC (polyvinyl chloride), in the chlorine bleaching of paper, and from natural sources such as volcanoes and forest fires. There have been many incidents of dioxin pollution resulting from industrial emissions and accidents; the earliest such incidents were in the mid 19th century during the Industrial Revolution.
The word "dioxins" may also refer to other similarly acting chlorinated compounds (see Dioxins and dioxin-like compounds).
Read more about Polychlorinated Dibenzodioxins: Chemical Structure of Dibenzo-p-dioxins, Historical Perspective, Sources of Dioxins, Sources of Human Intake, Metabolism, Toxicity, Health Effects in Humans, Toxic Effects in Animals, Agent Orange, Dioxin Exposure Incidents, Dioxin Testing