Dioxin, pronounced dy AHK suhn, is any of 75 related chemicals, all of which consist of
    carbon, chlorine, hydrogen, and oxygen.  However, the word dioxin is most commonly
    used to refer to only one of these chemicals, the compound 2, 3, 7, 8-tetrachlorodibenzo-
    p-dioxin (TCDD).  Some scientists consider TCDD to be the most toxic synthetically
    produced chemical.
    TCDD is a useless by-product of the manufacture of certain weedkillers and several other
    industrial processes.  Disposal of the chemical is difficult because it does not readily
    degrade (break down) in soil or water.  One of the most effective methods of disposing of
    dioxin is burning it at high temperatures.  Soil and water in parts of Canada, Europe, and
    the United States, however, have become contaminated with dioxin because of improper
    disposal of industrial wastes.  
    The health effects of TCDD are not completely understood. The chemical is extremely
    deadly to certain animals, but no human deaths have been directly linked to it. However,
    some people have developed such health problems as headaches, stomachaches, and a
    severe skin rash called chloracne as a result of exposure to dioxin.  Some researchers
    also believe the chemical may cause birth defects and cancer.  
    TCDD was first identified as a contaminant in 1957.  It was present in Agent Orange, a
    weedkiller used by U.S. armed forces in the 1960's and early 1970's, during the Vietnam
    War. Dioxin was not recognized as a major public health hazard until the mid-1970's.  

    Gary F. Bennett, Ph.D., Prof. of Biochemical Engineering, Univ. of Toledo.
    See also AGENT ORANGE; MISSOURI (Recent developments).  
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