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DDT

The term DDT refers to p,p'DDT, or p,p'dichlorodiphenyltrichloroethane. The compounds structure permits several different isomeric forms, such as o,p'DDT. The term DDT is also applied to commercial, technical products consisting predominantly of p,p'DDT, but also containing smaller amounts of other compounds, including p,p' and o,p'DDD (dichlorodiphenyldichloroethane) and p,p' and o,p'DDE (dichlorodiphenyldichloroethene). DDE has no commercial use. DDD was also used to kill pests, but its use has also been banned. One form of DDD has been used medically to treat cancer of the adrenal gland. These products together are known as total DDT or as Σ DDT.

DDT was first synthesized by a doctoral student Othmar Zeidler at University of Strasburg in 1873 but had never received any particular attention. In 1935 in the Laboratory of the J.R. Geigy DyeFactory Co. Basel, Switzerland, Paul Hermann Mller started research on new synthetic contact insecticides. Four years of intensive work led to the synthesis of dichlorodiphenyltrichloroethane (DDT). Mller found that DDT quickly killed flies, aphids, mosquitoes, walking sticks and Colorado potato beetles. Mller and the Geigy Corporation patented DDT in Switzerland (1940), England (1942) and U.S. (1943). Paul Hermann Mller was awarded the Nobel Prize in Physiology or Medicine in 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods."

The first pesticide products based on DDT, Gesarol and Neocide, were marketed in 1942. These formulations were brought to the notice of British and American medical entomologists at a time, during World War II, when supplies of pyrethrum (natural insecticide made from the dried flower heads of Chrysanthemum cinerariifolium and Chrysanthemum coccineum) were rapidly falling short of demand. Production was soon established on both sides of the Atlantic and they proved to be of enormous value in combating typhus and malaria malaria was, in fact, completely eradicated from many island areas in the Pacific Ocean.

After the war, DDT was widely used on a variety of agricultural crops and for the control of disease vectors as well. Peak usage occurred in 1962, when 80 million kilograms of DDT were used and 82 million kilograms produced.

In September 1962 a book Silent Spring written by Rachel Carson was published. The book catalogued the environmental impacts of the indiscriminate spraying of pesticides in the US, most notably DDT. The book questioned the logic of eleasing large amounts of these chemicals into the environment without fully understanding their effects on ecology and human health. Carson proposed a biotic approach to pest control as an alternative to DDT, claiming that DDT had been found to cause thinner egg shells and result in reproductive problems and death in bird population. The book resulted in a large public outcry that eventually led to DDT being banned in the US

DDT was subsequently banned for agricultural use worldwide, but its production and use in disease vector control continues to this day in some parts of the world. Up to date there are three countries, People's Republic of China, India and Ethiopia, registered by the WHO and the Stockholm Convention Secretariat, where DDT is being produced for insect borne disease control.

The Stockholm Convention Secretariat has been notified by Botswana, People's Republic of China, Ethiopia, India, Marshall Islands, Mauritius, Morocco, Myanmar, Senegal, South Africa, Swaziland and Republic of Yemen about DDT use. These countries are allowed to produce and/or use DDT for disease vector control in accordance with the World Health Organization recommendations and guidelines on the use of DDT and when locally safe, effective and affordable alternatives are not available. Parties that use and/or produce DDT are required by the Stockholm Convention to submit reports to the Secretariat and the WHO on the amount use, the conditions of its use and its relevance to their disease management strategies every three years.

 


Structure formula of DDT


3D structure of DDT