DDT

: For other uses, see DDT (disambiguation).

History

DDT was first synthesized in 1873 by Othmar Ziedler, but its insecticidal properties were not discovered until 1939, by the Swiss scientist Paul Hermann Müller, who was awarded the 1948 Nobel Prize in Physiology and Medicine for his efforts. DDT is the best-known of a number of chlorine-containing pesticides used in the 1940s and 1950s. It was used extensively during World War II by Allied troops and certain civilian populations to control insect typhus and malaria vectors (as a result nearly eliminating typhus). Civilian suppression used a spray on interior walls, which kills mosquitoes that rest on the wall after feeding to digest their meal; resistant strains are repelled from the area. Entire cities in Italy were dusted to control the typhus carried by lice. DDT also sharply reduced the incidence of biting midges in Great Britain.

Related Topics:
1873 - Othmar Ziedler - 1939 - Swiss - Paul Hermann Müller - 1948 - Nobel Prize - Pesticide - 1940s - 1950s - World War II - Typhus - Lice

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DDT was responsible for eradicating malaria from Europe and North America. Though today malaria is thought of as a tropical disease, it was more widespread prior to an extensive malaria eradication program carried out in the 1950s. Though this program was highly successful worldwide (reducing mortality rates from 192 per 100,000 to a low of 7 per 100,000), it was less effective in tropical regions due to the continuous life-cycle of the parasite and poor infrastructure. It was not pursued aggressively in sub-Saharan Africa due to perceived difficulties, with the result that mortality rates there were never reduced to the same dramatic extent, and now constitute the bulk of malarial deaths worldwide, especially following the resurgence of the disease as a result of microbe resistance to drug treatments and the spread of the deadly malarial variant caused by Plasmodium falciparum.

Related Topics:
1950 - Plasmodium falciparum

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DDT was also extensively used as an agricultural insecticide after 1945. DDT spraying in agricultural contexts was often orders of magnitudes greater in quantity than that employed for public health purposes, which required as little as 2g/m2 of DDT; by comparison, a single cotton field may have used a ton of DDT.

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By the 1950s, in some uses, doses of DDT and other insecticides had to be doubled or tripled as resistant insect strains developed. In addition, the evidence began to grow that the chemical became more concentrated at higher levels in the food chain.

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In the 1970s and 1980s DDT was banned in most developed countries. DDT was first banned from use in Norway and Sweden in 1970 and was not banned in the United Kingdom until 1984.

Related Topics:
1970s - 1980s - Norway - Sweden - 1970 - United Kingdom - 1984

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The U.S. ban of DDT

In 1962 Rachel Carson's book Silent Spring was published. The book argued that pesticides, and especially DDT, were poisoning both wildlife and the environment and also endangering human health. The public reaction to Silent Spring launched the modern environmental movement in the United States, and DDT became a prime target of the growing anti-chemical and anti-pesticide movements during the 1960s. In fact, Carson devoted a page of the book to thoughtful consideration of the relationship between DDT and malarial mosquitoes, but with cognizance of the phenomenon of development of resistance in the mosquito, concluding:

Related Topics:
1962 - Rachel Carson - Silent Spring - Pesticide - Environmental movement - 1960s

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:It is more sensible in some cases to take a small amount of damage in preference to having none for a time but paying for it in the long run by losing the very means of fighting . Practical advice should be ?Spray as little as you possibly can? rather than 'Spray to the limit of your capacity?

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rather than calling for a complete ban on antimalarial spraying.

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Charles Wurster, the chief scientist for the Environmental Defense Fund, was quoted in the Seattle Times of 5 October 1969, as saying: "If the environmentalists win on DDT, they will achieve a level of authority they have never had before. In a sense, much more is at stake than DDT." (Tren & Bate, 2004). However, as pesticide research was still immature when it was written, many of the claims made in Silent Spring were ultimately scientifically inaccurate. A 2004 study in the Journal of American Physicians and Surgeons concludes "Public pressure was generated by one popular book and sustained by faulty or fraudulent research. Widely believed claims of carcinogenicity, toxicity to birds, anti-androgenic properties, and prolonged environmental persistence are false or grossly exaggerated." http://www.fightingmalaria.org/research.php?ID=26&month=.

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5 October - 1969

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During the late 1960's, pressure grew within the United States for a ban on DDT. In January 1971, the US District Court of Appeals ordered Ruckelshaus to begin the deregistration procedure for DDT. Initially, after a six-month review process, the EPA's first Administrator William Ruckelshaus rejected an outright ban, citing studies from the EPA's internal staff that stated that DDT was not an imminent danger to human health and wildlife. However, the findings of these staff members were criticized, as they were performed mostly by economic entomologists inherited from the United States Department of Agriculture, whom many environmentalists felt were biased towards agribusiness and tended to minimize concerns about human health and wildlife. The decision not to ban thus created public controversy.

Related Topics:
EPA - William Ruckelshaus - United States Department of Agriculture

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The EPA held seven months of hearings in 1971-1972, with scientists giving evidence both for and against the use of DDT. At the end of the hearings, the hearing examiner, Edmund Sweeney, ruled that the scientific evidence provided no basis for banning DDT. In the summer of 1972 Ruckelshaus reviewed evidence collected during the agency's hearings as well as reports prepared by two DDT study groups (the Hilton and Mrak Commissions) that had both come to the opposite conclusion. He did not actually attend any of the EPA commission's hearings however, and according to his aides did not read any transcripts of it. Ruckelshaus overturned Sweeny's ruling and announced a ban on virtually all uses of DDT in the U.S., where it was classified in EPA Toxicity Class II. Ruckelshaus argued that the pesticide was "a warning that man may be exposing himself to a substance that may ultimately have a serious effect on his health." (Tren & Bate, 2004)(Milloy, 1999).

Related Topics:
EPA - Hilton - Mrak Commission

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The 1970s ban in the U.S. took place amid a climate of public mistrust of the scientific and industrial community, following such fiascoes as Agent Orange, Love Canal, and use of the hormone diethylstilbestrol (DES). In addition, the fact that the bald eagle was placed on the endangered species list in large part because of the overuse of DDT was also a strong factor leading to its banning in the United States.

Related Topics:
1970s - Agent Orange - Love Canal - Diethylstilbestrol - Bald eagle

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International regulation of DDT

As of 2005, DDT continues to be used in other (primarily tropical) countries where mosquito-borne malaria and typhus are greater health problems than DDT's potential toxicity. Use of DDT in public health to control mosquitoes is primarily done inside buildings and through inclusion in household products and selective spraying; this greatly reduces environmental impact compared to the earlier widespread use of DDT in agriculture. It also reduces the risk of resistance to DDT. A FAQ on how DDT is currently used against malaria is available at http://www.malaria.org/DDTcosts.html. This use only requires a small fraction of that previously used in agriculture; for the whole country of Guyana, covering an area of 215,000 km², the required amount is roughly equal to the amount of DDT that might previously be used to spray only 4 km² of cotton during a single growing season http://www.cdc.gov/ncidod/eid/vol3no3/roberts.htm.

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The Stockholm Convention, ratified in 2001 and effective as of 17 May 2004, calls for the elimination of DDT and other persistent organic pollutants, barring health crises. The Convention was signed by 98 countries and is endorsed by most environmental groups. However a total elimination of DDT use in many malaria-prone countries is currently unfeasible because of the prohibitive costs of alternative insecticides. Countries can apply for exemptions to use DDT for health reasons. The WHO and United Nations Environment Programme (UNEP) review the DDT exemption every three years. Rules and regulations regarding the trade, storage and use of DDT under the convention have made DDT use more difficult and expensive.

Related Topics:
Stockholm Convention - 2001 - 17 May - 2004

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