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 10 million hectares of agricultural land were affected (16). In some areas, TCDD concentrations in soil and water were hundreds of times greater than the levels considered “safe” by the US EPA (16, 18). Overall, more than 20% of South Vietnam's forests were sprayed at least once over a 9-year period (18).

The legacy of the spraying during the war lives on. Approximately 17% of the forested land had been sprayed, and to this day, dioxins contained in the chemicals remain in the soil. In many places, the natural foliage has been replaced by invasive plant species. Animal species diversity was also significantly affected by the chemicals. For instance, a Harvard biologist found 24 species of birds and 5 species of mammals in a sprayed forest, while in two adjacent sections of unsprayed forest, there were 145 and 170 species of birds and 30 and 55 species of mammals (19).

Movement of dioxins through the food web has resulted in bioconcentration and biomagnification (20). The areas that were most heavily contaminated with dioxins are the sites of former US air bases where the chemicals were handled (17). The Vietnam Red Cross reported as many as 3 million Vietnamese people have been affected by Agent Orange, including at least 150,000 children born with birth defects (21).

The problem with dioxins is that they are highly toxic, with no safe levels of exposure, and the chemicals take a tremendous amount of time to break down (22). This class of chemicals is produced as a by-product during chemical production for legitimate use or when chlorinated chemicals are burned. Vietnam is not the only place in the world where dioxins pose a threat. Seveso, Italy, also experienced an environmental issue due to dioxin.