2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a polychlorinated dibenzo-p-dioxin (sometimes in short but inaccurately also called dioxin) with a chemical formula C
12H
4Cl
4O
2. TCDD is a colorless solid with no distinguishable odor at room temperature. It is usually formed as a side product in organic synthesis and burning of organic materials.
TCDD is the most potent compound (congener) of its series (polychlorinated dibenzodioxins, known as PCDDs or simply dioxins) and became known as a contaminant in Agent Orange, a herbicide used in the Vietnam War.[3] TCDD was released into the environment in the Seveso disaster.[4] It is a persistent environmental contaminant usually present in a complex mixture of dioxin-like compounds, and is a carcinogen.[5]