This article is about the chemical. DDT is also a move in Professional wrestling, see Professional wrestling throws. DDT is also the name of a computer debugger. DDT is also the name of a Russian rock band.

DDT or Dichloro-diphenyl-trichloroethane (ClC₆H₄)₂CH(CCl₃) is a colourless crystalline substance which is practically insoluble in water but highly soluble in fats and most organic solvents.

DDT was developed as the first of the modern insecticides early in World War II. It was initially used with great effect to combat mosquitoes spreading malaria, typhus, and other insect-borne human diseases among both military and civilian populations. [1] http://www.epa.gov/history/topics/ddt/01.htm

In the early 1960s, Rachel Carson, through publication of the book Silent Spring, aroused public opinion against DDT with her claim that DDT caused cancer and harmed bird reproduction by thinning egg shells; the resulting outcry eventually led to the pesticide being banned for agricultural use worldwide and was one of the signature events in the birth of the environmental movement.

Contents

1 Properties 2 History 2.1 Dangers 2.2 The banning of DDT 2.3 Support for using DDT 3 Notes 4 External links 4.1 DDT Ban Problems 4.2 Dead Links

Properties

DDT is created by the reaction of trichloroethanol with chlorobenzene (C₆H₅Cl). Trade or other names for DDT include Anofex, Cesarex, Chlorophenothane, Dedelo, p,p'-DDT, Dichlorodiphenyltrichloroethane, Dinocide, Didimac, Digmar, ENT 1506, Genitox, Guesapon, Guesarol, Gexarex, Gyron, Hildit, Ixodex, Kopsol, Neocid, OMS 16, Micro DDT 75, Pentachlorin, Rukseam, R50 and Zerdane.

DDT is persistent in the environment. It has a reported half life of 26 days in river water (U.S. EPA, 1989), but 15 years in most soils. It is also immobile in most soils. Routes of loss and degradation include runoff, volatilization, photolysis and biodegradation (aerobic and anaerobic). These processes generally occur slowly. Breakdown products in the soil environment are DDE (1,1-dichloro-2,2-bis(p-dichlorodiphenyl)ethylene) and DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane), which are also highly persistent and have similar chemical and physical properties.

History

DDT was first synthesized in 1873, and its insecticidal properties were discovered by the Swiss scientist Paul Hermann Müller in 1939 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 extensively used during World War II among Allied troops and certain civilian populations to control insect typhus and malaria vectors. Entire cities in Italy were dusted to control the typhus carried by lice. DDT was also extensively used as an agricultural insecticide after 1945. In the 1950s, in some uses doses of DDT and other insecticides had to be doubled or tripled as some resistant insect strains developed, and evidence began to grow that the chemical was concentrated in the food chain.

Civilian suppression of typhus and malaria vectors (mosquitoes) uses a spray on interior walls, which kills mosquitoes which rest on the wall, while resistant strains are repelled from the area, and thus humans are protected. The compound is stable and concentrates in fatty tissue, reaching dangerous levels in carnivores high in the food chain. It is also excreted in milk.

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 insect resistance to DDT, microbe resistance to drug treatments and the spread of the deadly malarial variant caused by Plasmodium falciparum.

Dangers

When present at comparatively low levels in some species of raptors, DDE, a DDT metabolite, causes the birds to lay eggs with thin shells. Other species are relatively unaffected; for example, the chicken continues to produce normal eggs despite high levels of exposure. DDT and its metabolic products accumulate through the food chain, with apex predator s such as raptors having a higher concentration of the chemicals than other animals sharing the same environment; several species were pushed close to extinction prior to the ban as a result. At the time of the ban, the available research was based on DDT; only later research demonstrated the greater significance of DDE.

DDT is not particularly toxic to humans, compared to other widely used pesticides.

Because of DDT's singular effectiveness in the control of the mosquito, which vectors malaria, it is still used in many countries throughout the world where malaria has proven difficult to control. Use of DDT to control mosquitoes is primarily done inside buildings and through inclusion in household products and selective spraying; this greatly reduces the risk of strong environmental impact.

DDT is an organochlorine. Some organochlorines have been shown to have weak estrogenic activity, that is, they are chemically similar enough to estrogen to trigger hormonal responses in contaminated animals. This sort of activity has been observed in DDT in laboratory studies involving mouse and rat test subjects, but available epidemiological evidence does not indicate that these effects have occurred in humans as a result of DDT exposure.

Studies of alligators in Florida swamps have found extensive oestrogenation, possibly due to high levels of DDT exposure. Many male crocodiles in the area have deformed genitalia and feminised bodily features, while their eggs are showing high rates of infertility and abnormal fetal development. Some researchers believe that this is echoed in the human population. Fertility studies in Scandinavia, where DDT was widely used to control pests, have found that the average male sperm count has dropped by almost 50% since DDT started to be used, while there is an increased rate of certain cancers of the reproductive organs compared to former years; however, these studies have not demonstrated a causative link between DDT and other effects.

The banning 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 book received little support from the mainstream scientific community. Nonetheless, the public reaction to Silent Spring launched the modern environmental movement, and DDT became a prime target of the growing anti-chemical and anti-pesticide movements during the 1960s.

DDT was first banned from use in Norway and Sweden in 1970 (it was not banned in the United Kingdom until 1984). In the United States, the EPA's first Administrator, Environmental Defense Fund supporter William Ruckelshaus, defying his science advisors, announced a ban in 1972 on virtually all uses of DDT in the U.S., where it is classified in EPA Toxicity Class II. Despite the U.S. ban on usage, chemical factories in the U.S. continued to manufacture and export DDT to Third World countries for years.

The 1970s ban in the U.S. took place amid a climate of public mistrust of the scientific and industrial community, following such fiascos as Agent Orange, Love Canal, and use of the hormone diethylstilbestrol (DES). In understanding the public policy landscape that led to the ban, it is important to realize that there were essentially no restrictions in the U.S. on pesticide manufacture and use during the 1940s and 1950s. This, coupled with the fact that fewer people in the '60s were as concerned with environmentalism as people are today, led to impure products, little knowledge of any risks on the part of the pesticide users, overapplication, and ignorance of any long-term environmental damage that might occur.

In this light, it is not surprising the DDT was overapplied, and its accumulation in the soil and in sensitive watersheds has been rigorously documented. There was little question that DDT accumulation in the environment led to the precipitous decline in raptor populations starting around 1960, with many birds including the bald eagle having been placed on the endangered species list during this period.

As of 2004, 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.

Support for using DDT

Controversy remains in some scientific circles over DDT's actual toxicity, however. Some scientists have protested that the laboratory animal studies done in 1969 (and which led to the banning of DDT in much of the developed world) which showed that DDT caused an increase in liver cancer was inconsistent with observations in the wild, given that DDT had been used widely during the preceding three decades with no increase in liver cancer in any of the human populations among whom it had been sprayed.

When the World Health Organization investigated the 1969 mouse study, they found that both experimental and control groups had developed a surprising number of tumors. Further investigation revealed that the food fed to both groups were moldy and contained aflatoxin, a carcinogen. When the tests were repeated using uncontaminated foods, neither group developed abnormal numbers of tumors.

In many African nations, the health problems resulting from millions of malaria per year are viewed as greater than the potential dangers 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 also began permiting its use in anti-malarial efforts despite a threat that its agricultural products to Europe would be banned as a result. One of the arguments against continuing its ban was that DDT was being used anyway in uncontrolled amounts.

Dr. Elizabeth Whelan , the president of the American Council on Science and Health claims that 60 million or more lives "have been needlessly lost since the ban on DDT took effect. ... It's a real tragedy that DDT has been so demonized over the years by activist organizations such as Environmental Defense and the regulatory bodies that they have duped."¹

Whelan's estimates come from estimates that 2.5 million people die of malaria each year: mostly African children. According to the U.N. World Health Organization (WHO), malaria kills one child under the age of 5 every 30 seconds.

However, the ban on DDT did not significantly interfere with its use as an anti-malarial agent; malarial deaths remain depressed in most of the world, except for Africa, where they have been climbing steadily since 1900. The World Health Organization attributes most of the increase in malarial deaths to insect resistance to pesticides (like DDT) and malaria pathogen resistance to drug treatments, in addition to generally poor health of much of the African population. However, it continues to fight against a total ban on DDT use (advocated for by the World Wildlife Fund amongst other organisations).

Notes

¹ Some detractors have raised questions about the credibility of the American Council on Science and Health, since according to the Congressional Quarterly's Public Interest Profiles Whelan's organization received more than 75 percent of their funding from the chemical and pharmaceutical industry. See the article on ACSH for more details.

External links

• DDT and its Derivatives - Environmental Aspects http://www.inchem.org/documents/ehc/ehc/ehc83.htm by International Programme on Chemical Safety (1989)
• 100 things you should know about DDT http://www.junkscience.com/ddtfaq.htm - History, myths, and facts about DDT
• Pesticide residues in food 2000 : DDT http://www.inchem.org/documents/jmpr/jmpmono/v00pr03.htm
• PESTICIDE RESIDUES IN FOOD - 1984 http://www.inchem.org/documents/jmpr/jmpmono/v84pr49.htm
• Areobic pathway of DDT metabolization http://umbbd.ahc.umn.edu/ddt/ddt_map.html - biological half-life of 8 years.
• Anaeobic pathway of DDT metabolization http://umbbd.ahc.umn.edu/ddt2/ddt2_map.html
• Lecture Notes http://jan.ucc.nau.edu/doetqp/courses/env440/lectures/lec25/lec25.html
  • After 17 years, 39% DDT remaining in soil.
  • DDT levels in food chain of Lake Kariba, a lake in Africa.
  • Table of DDT in USA human body fat 1942-1978.
• Environmental Fate Evaluation of DDT, Chlordane and Lindane http://www.ces.clemson.edu/ees/lee/organochlorines.html - Examination of environmental fate using EXAMS computer simulation.
• DDT, Eggshells, and Me http://www.reason.com/rb/rb010704.shtml outlines the evidence that the DDT metabolite DDE is associated with eggshell thinning.

DDT Ban Problems

• The Mosquito Killer http://www.gladwell.com/2001/2001_07_02_a_ddt.htm - Fred Soper, Malaria Fighter (also available: PDF version http://www.gladwell.com/pdf/malaria.pdf )
• How many must die? http://www.techcentralstation.com/081403C.html - Lack of use of insecticides during spread of West Nile virus
• Rachel Carson's Ecological Genocide http://www.frontpagemag.com/Articles/ReadArticle.asp?ID=9169 - World threatened by millions dying due to DDT ban, Carson's Silent Spring, and EPA Administrator/Environmental Defense Fund supporter William Ruckelshaus.
• Better Living Through Chemistry http://www.washingtonmonthly.com/features/2003/0303.gourevitch.html - summary of DDT ban problems
• Malaria and the DDT Story http://www.iea.org.uk/files/upld-publication26pdf?.pdf (PDF, 112 pg) - Institute of Public Affairs review of the devastation malaria has caused in the past and the economic problems a proposed worldwide ban on the use of DDT is causing for a developing African nation, Mozambique.
• Who's Kidding W.H.O.? Strange Doings http://healthfactsandfears.com/high_priorities/phantom/2002/who052202.html - Phantom Health Menaces comment about WHO ban on DDT and current interests.
• [2] http://www.acsh.org/healthissues/newsID.442/healthissue_detail.asp and [3] http://www.acsh.org/factsfears/newsID.319/news_detail.asp - ACSH articles on DDT use against malaria

Dead Links

• Dr. Whelan Op-ed http://www.washtimes.com/commentary/20021017-7408114.htm