Dioxin

To deprive their enemy of food and cover during the Vietnam War, the U.S. military sprayed large quantities of herbicides. More than 547,000 sq mi (1.4 million ha) of terrain were sprayed at least once. The most commonly used herbicide was a 50:50 mixture of 2,4,5-T and 2,4-D, known as Agent Orange. More than 46 million lb (21 million kg) of 2,4,5-T and 55 million lb (25 million kg) of 2,4-D were sprayed during this extensive military program.

An important aspect of the military use of herbicides in Vietnam was contamination of the 2,4,5-T by TCDD. A concentration as large as 45 ppm was measured in Agent Orange, but the average concentration was about 2 ppm. In total, 243-375 lb (110-170 kg) of TCDD was sprayed with herbicides onto Vietnam.

Because TCDD is known to be extremely toxic to some laboratory animals, there has been tremendous controversy over the possible short and long-term effects of exposure of soldiers and civilians to TCDD in Vietnam. Although claims have been made of effects in exposed populations, the studies have not been convincing to many scientists, and there is still controversy. The apparent, mainstream opinion from the most rigorous epidemiological studies suggests that large toxic effects have not occurred, which is encouraging. It is also likely that the specific effects of TCDD added little to the very substantial ecological effects caused by the use of military use of herbicides, and other weapons of mass destruction, during the Vietnam War.