Dichloro-diphenyl-trichloroethane, commonly known as DDT, is a synthetic organic chemical compound that was first made in 1874 by Othmar Zeidler, an German-Austrian chemist.
In 1939, Paul Hermann Müller, a Swiss chemist working for Geigy Pharmaceutical, discovered its pesticidal qualities. It was soon put to good use by Allied forces in World War II to help control malaria and typhus, especially in the Asian and Pacific theatres.
Following the war it was used widely with great success to eliminate the last pockets of malaria from North America and Europe. In 1955 the World Health Organization started a program to eradicate malaria worldwide, largely through the spraying of DDT. Brazil, Egypt, the former Soviet Union and several Asian and Caribbean countries were freed from malaria, and 700 million people from risk of infection.
DDT was also widely adopted as an agricultural pesticide and it was, perhaps, overused by farmers.
Campaign to ban DDT
Although not toxic in small amounts, DDT was claimed, when accumulated in bodies through the food chain, to have an adverse effect on bird life, particularly raptors. In 1962, naturalist Rachel Carson published Silent Spring, a bestselling book that campaigned for regulation of the use of DDT.
- Rachel Carson sounded the initial alarm against DDT, but represented the science of DDT erroneously in her 1962 book Silent Spring. Carson wrote "Dr. DeWitt's now classic experiments [on quail and pheasants] have now established the fact that exposure to DDT, even when doing no observable harm to the birds, may seriously affect reproduction. Quail into whose diet DDT was introduced throughout the breeding season survived and even produced normal numbers of fertile eggs. But few of the eggs hatched." DeWitt's 1956 article (in Journal of Agriculture and Food Chemistry) actually yielded a very different conclusion. Quail were fed 200 parts per million of DDT in all of their food throughout the breeding season. DeWitt reports that 80% of their eggs hatched, compared with the "control"" birds which hatched 83.9% of their eggs. Carson also omitted mention of DeWitt's report that "control" pheasants hatched only 57 percent of their eggs, while those that were fed high levels of DDT in all of their food for an entire year hatched more than 80% of their eggs. 
Then, public sentiment escalated into calling for an outright ban of DDT and other synthetic pesticides.
In 1970, DDT was banned in Norway and Sweden. The U.S. banned it in 1972, and the UK in 1984. Most developed countries have banned its use but it is still used for disease control in some tropical countries where no other methods exist. The quantities required for public welfare are a small fraction of the amount previously used for agricultural purposes.
In 2001, 98 countries ratified the Stockholm Convention, which calls for the elimination of DDT and other persistent organic chemicals after May 17, 2004, except for emergency health crises. However, in the absence of a suitable replacement, DDT is still allowed for disease vector control. In 2006 the World Health Organization announced that it will use DDT for indoor residual spraying (IRS) in epidemic and endemic areas to reduce childhood mortality from malaria. 
Notes and References
- In 1948 Müller was awarded the Nobel Prize in Physiology or Medicine "for his discovery of the high efficiency of DDT as a contact poison against several arthropods."
-  WHO - Indoor Residual Spraying - position paper