Colourless chemical pesticide, dichlorodiphenyltrichloroethane, used to eradicate disease-carrying and crop-eating insects. It was originally isolated in Germany in 1874, but it was not until 1939 that the Swiss Nobel Prize-winning chemist Paul Müller recognized it as a potent nerve poison on insects. First used heavily in World War II for preinvasion spraying, DDT was disseminated in great quantities thereafter throughout the world to combat yellow fever, typhus, elephantiasis, and other insect-carried diseases. In India, DDT reduced malaria from 75 million cases to fewer than 5 million cases in a decade. Crops and livestock sprayed with DDT sometimes as much as doubled their yields.
With the publication of the American marine biologist Rachel Carson's Silent Spring in 1962, suspicion grew that DDT, by entering the food chain and eventually concentrating in higher animals, caused reproductive dysfunctions, such as thin eggshells in some birds. Some insect pests also gradually developed DDT-resistant strains whose populations grew unchecked while their natural predators, such as wasps, were being eradicated by spraying. For these reasons, DDT has since been banned in many nations, although it may still be used in cases of extreme health emergencies.