DDT is, technically, dichloro-diphenyl-trichloroethane, a chemical compound that was produced in a Scottish laboratory in 1873 by Othmar Zeidler. In 1939, Paul Mueller, working in Switzerland, discovered that DDT was in fact an insecticide, and was awarded the Nobel Peace prize for his work. During World War II, DDT was used to control disease and body lice. DDT was one of the factors in eliminating malaria from the United States because of its effect on mosquitoes (an effect that is still undergoing intensive study.)
DDT was enthusiastically embraced as an insecticide, and used not only for disease control in humans, but for protecting crops from insects, as well. During the peak of its popularity, as much as 220 million pounds of DDT was used per year in the United States.
The Environmental Protection Agency website discusses some basic facts about DDT. It is soluble in fats, and is stored in the bodies of predators, thereby migrating through the food chain, as well as the atmosphere. Its half-life in soil is about 16 years. One of its most famous properties is to cause the deterioration of egg shells, but the range and validity of that effect is disputed, with varying degree of bitterness, by critics as well as sympathizers of Rachael Carson’s book, “Silent Spring,” published in 1962. There is consensus that the research in the book is out-dated. Supporters of the DDT ban generally rely on more modern studies and opinion.
DDT’s reported ill effects on humans range from uncomfortable reactions to cancer-causing tendencies. There have been definitive studies on small mammals, but there have been no instances of cancer in workers who were exposed daily to DDT over a period of years, and even though careful studies have been made, there remains no proof of mammarian cancer in women.
Carson’s book has been credited with inspiring the ban on DDT as a crop-protection device which was implemented in 1972 by the newly formed Environmental Protection Agency. The ban was effectively placed on medical use as well, not only in the United States, but upon countries that traded with US and other European Markets agriculturally.
Partly because of this restriction upon its trade partners, DDT has been used much more sparingly in the tropical climates where mosquitoes are a large factor in the control of malaria. The tendency of insects to develop resistance to DDT has also contributed to less use, although certain strategies for its use are still recognized as an effective deterrent for malaria. The Stockholm agreements concerning DDT use now include recognition of the medical value (including cost effectiveness) of DDT use in poor countries that cannot afford the expensive treatments, and that suffer high death rates from tropical disease with less-effective but cheaper treatments.
The current international focus on DDT highlights trade agreements which restrict total use of DDT when medical use would be beneficial for a struggling tropical economy, for instance restricting in-house wall coating because a country exports flowers to Europe. Another topic of current debate is the tendency of insects to develop quick resistance to DDT, thereby strengthening the carriers of the disease. There is also discussion of the cost of alternative malaria treatments, and the consequences, or even the necessity, of a permanent and total ban of the chemical.