15-108 Science Matters:DDT & Modern Environmental Movement II

Lead: In 1962 Rachel Carson animated the national conversation with "Silent Spring," an explosive book describing the environmental havoc wreaked by DDT.

Intro.: A Moment in Time with Dan Roberts.

Content: At first DDT, dichloro-diphenyl-trichloroethane, seemed a miracle. Modern agricultural practices had produced increased crop yields but had also opened the way to greater infestation by insect pests. Various chemical insecticides were tried, but not until the late 1930s did there appear to be a true solution to the problem of insect control. Immediately upon USDA approval of DDT for use on plants and agricultural commodities, farmers snatched it up. Crop production soared! By interrupting respiration at the cellular level, the grayish-white powder killed virtually every insect that consumed it. The insects literally suffocated from the inside out.

DDT was used extensively--some would say indiscriminately--in the years following World War II, but then the problems began to surface. The compound is a very effective poison against insects but, in sufficient quantities, also against birds, squirrels, the family cat and sometimes humans. Further, DDT is biologically persistent, meaning that it decomposes very slowly over many years. It remains in the environment, and is stored in fat. Grasshoppers, dying by the millions in a field, are snatched up by field mice; they in turn are eaten by predatory birds; and so on, up the food chain. Finally, DDT also kills all the good non-pest insects, many of which eat the pests naturally with no negative impact. Crop damage from pest infestation actually increased following the adoption of DDT.

In 1962 author and biologist Rachel Carson released "Silent Spring." The book was a sensation and provoked calls for reform. Eleven years later, in 1973, the USDA banned the use of DDT in the United States. The controversy, however, went a long way toward sparking the modern environmental movement. Rachel Carson never saw the full impact of her work; she died in 1964.

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