Risk Assessment: Tools, Techniques, and Their Applications

4.5 Agent Orange

Agent Orange was the code name for one of the herbicides and defoliants used by the US military as part of its herbicidal warfare program during the Vietnam War (16, 17). The campaign called Operation Ranch Hand involved spraying the countryside with the chemicals with the goal of defoliating the jungles and destroying crops.

Agent Orange was a 50:50 mixture of 2,4,5-T/2,4-D (17). It was manufactured for the US Department of Defense primarily by Monsanto Corporation and Dow Chemical. The 2,4,5-T used to produce Agent Orange was later discovered to be contaminated with 2,3,7,8-tetrachlorodibenzodioxin, an extremely toxic dioxin compound. It was given its name from the color of the orange-striped 55 US gal (200l) barrels that it was shipped in (17). It was the most widely used herbicide during the war.

During the Vietnam War, between 1962 and 1971, the US military sprayed nearly 20,000,000 US gal (75,700,000 l) of chemical herbicides and defoliants in Vietnam, eastern Laos, and parts of Cambodia, as part of the operation (16, 17).

Air Force records show that at least 6542 spraying missions took place over the course of the operation (17). Approximately 12% of the total area of South Vietnam had been sprayed with defoliating chemicals by the end of the war. It is estimated that it was sprayed at an average concentration of up to 13 times the recommended United States Department of Agriculture (USDA) application rate for domestic use. In South Vietnam, an estimated ...