From 1961 to 1971 the US government sprayed more than 21 million gallons of herbicides and defoliants over vast areas of southern and central Viet Nam, and to a lesser extent in Laos and Cambodia. The most commonly used herbicide was called Agent Orange. Two-thirds of these chemicals were contaminated with TCDD - dioxin, a highly toxic substance linked to at least thirteen classes of cancers and several birth defects. 

According to research by Jeanne Stellman et al of Columbia University a least 4.8 million Vietnamese civilians were living in the areas sprayed by airplane. This figure does not include the US soldiers, the Vietnamese soldiers (on both sides of the war), Vietnamese civilians who traveled through the sprayed regions, or those that worked on the military bases which were frequently sprayed.

5 million acres of mangrove and upland forest were defoliated and 500,000 acres of crops were destroyed, approximately 12% of southern Viet Nam.

In addition, the US Department of Defense used dioxin contaminated herbicides along the DMZ in Korea and performed tests of these herbicides at numerous locations throughout the US, Thailand, Puerto Rico, and New Brunswick, Canada. Communities such as Midland, MI, Nitro, WV, Newark Bay, and Gulfport, MS are still dealing with the ongoing impacts of the manufacture or storage of the toxic herbicides by Dow, Monsanto, Diamond Shamrock, Hercules and the other manufacturers of the herbicides.