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Pesticides at War

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In the Vietnam War (1959–1975), a number of herbicides were used by the US against North Vietnam and Viet Cong forces. These included Agents Pink, Green, Purple, Blue, White, and Orange. Rachel Carson does not refer to these chemicals in Silent Spring, as their use only began in 1961.


Image of US armed personnel carrier spraying Agent Orange in VietnamThe best known and most widely used was Agent Orange. This herbicide was comprised of a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Agent Orange was later found to be contaminated by dioxin, which has been called “possibly the most toxic molecule ever synthesized by man”.

Agent Orange and other herbicides were applied from the air to defoliate rainforests to give less cover to enemy troops, and to destroy crops to starve the enemy. Nearly 20,000,000 gallons were sprayed from 1962 to 1971. Resulting food shortages affected millions, mostly in South Vietnam.


The chemicals also caused burns and disfigurement to human skin. Many newborns suffered physical and mental disabilities. Cancer rates increased, with dioxin the likely cause.

Not only the Vietnamese were affected. US and Allied war veterans who served in sprayed areas or handled the chemicals, showed increased rates of several types of cancer, and skin and respiratory disorders. Birth defects appeared higher in the children of returned veterans.

Large areas of forest were destroyed, and then invaded by bamboo and other grasses. This prevented regrowth of the forest trees, thus changing the biodiversity and ecology for the long term.

The dioxin in Agent Orange is persistent, and can still be detected 40 years later.

Several countries have used Agent Orange in weed control and other industrial operations such as forest clearing for mining and dam construction.