dioxin science definition

Any of several toxic hydrocarbons that occur as impurities in petroleum-derived herbicides, disinfectants, and other products. Dioxins are composed of two benzene rings connected by two oxygen atoms, and the most familiar kind, called TCDD, has two chlorine atoms attached to each benzene ring. TCDD was once thought to cause cancer and birth defects, but subsequent research showed it to have only mild toxic effects except at very high exposure levels.