Defoliant.

Another chemical at the center of controversy was Agent Orange. Agent Orange was a defoliant used extensively in the U.S. war in Vietnam to deny ground cover and food to North Vietnamese guerrillas by destroying forests and crops. Named for the orange stripe painted on fifty-five-gallon barrels for identification, it was developed by the army in the 1950s as an alternative to biological weapons. It was a combination of two herbicides — 2,4-D (n-butyl-2,4, dichlorophenoxyacetate) and 2, 4, 5-T (n-butyl-2,4,5-trichlorophenoxyacetate) — and was tremendously effective. By 1970, 11.2 million gallons had been dropped by airborne C-123 cargo planes, destroying the plant life of 4.5 million acres. In addition to the areas officially targeted, fruit trees, mangrove swamps, and crops were also destroyed by leaky spray nozzles, wind drift, and vaporization from the heat. The cumulative effect crippled the Vietnamese economy and did substantial damage to the environment. In...