2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN

The term dioxins refers to chlorinated hydrocarbons containing a dibenzo-p-dioxin structure (two benzene rings conjoined at their para carbons by two oxygen molecules). The nomenclature for chlorinated dibenzodioxins (CDD) is based on the number and position of the chlorine molecules and include mono- (MCDD), di- (DCDD), tri- (TrCDD), tetra- (TCDD), penta- (PeCDD), hexa- (HxCDD), hepta- (HpCDD), and octachlorinated (OCDD) congeners. There are 75 congeners in total. The 2,3,7,8-tetrachlorodienzo-p-dioxin (2,3,7,8-TCDD) congener is the most familiar congener due in part to its toxicity in animal models, its widespread distribution and persistence in the environment, its bioaccumulation potential, and because most data pertain to this congener. Dioxins in pure form are colorless solids and are formed as combustion products. Dioxins may be formed during the combustion of organic material in the presence of halogens, especially chlorine (and bromine), during waste incineration and forest fires. They also occur as contaminants in herbicides.
Dioxin was a contaminant of Agent Orange and possibly responsible for some of the adverse health effects associated with exposure to the defoliant. Dioxin was the poisoning agent in a high-profile political incident in 2004. Dioxin was ultimately identified as the cause of the disfiguring acne-like skin (chloracne) condition suffered by Ukrainian opposition leader Viktor Yushchenko a few months prior to the first presidential election. The suspicion was that the dioxin was placed into soup consumed by Mr Yushchenko. The acne-like skin condition is a recognized hallmark of dioxin poisoning in humans. The actual intake of dioxin in this incident is unknown.