| Link to graphic showing the structure of these two molecules |
The most clearly established health effect of dioxin in humans is a skin eruption called chloracne. An explosion in a chemical factory in Seveso, Italy in 1976 contaminated the vicinity with dioxin and caused many cases of chloracne.
Many Vietnam veterans believe that exposure to dioxin while they served in Vietnam later caused them to father babies with birth defects. However, careful study of several thousand families in the area of Atlanta, Georgia revealed that the % of babies born with birth defects to fathers who had served in Vietnam (2-3%) was the same as for fathers who had served elsewhere in the military and the same for fathers who had never had military service at all.
A more recent study (1987) of Vietnam ground troops who served in sprayed areas revealed that they averaged 4 parts per trillion (ppt) of dioxin in their blood. The half-life of dioxin in the body is 6-10 years so assuming that these men got all their dioxin exposure in Vietnam, they would have had some 20 ppt (the maximum permissible amount in U.S. civilians) at that time. But this assumption is certainly false. Dioxins are produced whenever organic matter is burned (backyard barbecues, municipal incinerators, wood-burning stoves). Furthermore, 4 ppt of dioxin was also found in the blood of an otherwise matched group of veterans who did not serve in Vietnam. U.S. civilians with no known exposure to TCDD should not have serum levels of TCDD exceeding 20 ppt. The highest level found in persons living near Seveso was 1,800 ppt.
The death rate of Vietnam veterans - especially in the years immediately following their service - has been substantially higher (45% in the first 5 years after service) than that of veterans who served at the same time in other locations such as Korea, Germany, and the United States. Almost all of these excess deaths were the result of injuries: motor vehicle accidents, suicide, homicide. The health of Vietnam veterans is still being monitored and, as they age, more organic diseases, like cancer, will be seen. Perhaps those men will have elevated rates of such disease. But it is now clear that these will not have been caused by agent orange.
In the early days, some batches of 2,4,5,-T were contaminated by as much as 25-50 ppm of dioxin. Considerable uncertainty exists over the degree of contamination of agent orange used in Vietnam with estimates ranging from 5 ppm to less than 1 ppm. It is now possible to manufacture 2,4,5-T with less than 0.1 ppm of dioxin. Despite these facts and despite the lack of evidence that agent orange was responsible for the health problems of Vietnam veterans and their families, manufacture of 2,4,5-T has been halted and the companies involved have set up a trust fund (of more than $200 million) to benefit veterans who feel that they have been injured by the herbicide.
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