DDT

DDT (or dichlorodiphenyltrichloroethane) is an insecticide useful in combating malaria by killing mosquitos who transmit the disease to humans. According to the U.N. World Health Organization (WHO), malaria kills one child under the age of 5 every 30 seconds.

According to a Washington Times article,

DDT was discovered by a Swiss chemist, Paul Herman Muller, just before the start of World War II. It was used throughout the war for lice prevention. Entire cities in Italy were dusted to control the typhus carried by the lice. DDT was effective against insects and it seemed to work forever. In addition, it was virtually harmless to humans. In 1948, Mr. Muller won a Nobel Prize for his discovery.

But in 1972, DDT was banned in the United States, because its agricultural use by farmers had led to its entering the food chain. According to a 1966 study, the average American teenager consumed 12 mg/year of DDT.

In 2001, after a five-year ban led to more than a ten-fold increase in malaria cases, South Africa permitted its use again. Uganda is considering using it as well, although it fears the loss of aid form international agencies who want DDT to remain banned.