DDT

: For other uses, see DDT (disambiguation).

Properties

DDT is a colourless crystalline substance which is practically insoluble in water but highly soluble in fats and most organic solvents.

Related Topics:
Crystal - Water - Solvent

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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.

Related Topics:
Trichloroethanol - Chlorobenzene

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DDT has potent insecticidal properties; it kills by opening sodium channels in insect neurons, causing the neuron to fire spontaneously. This leads to uncontrolled spasming and eventual death. DDT was responsible for eradicating malaria from Europe and North America, and was also extensively used as an agricultural insecticide after 1945. Insects with certain mutations in their sodium channel gene may be resistant to DDT and other similar insecticides.

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Environmental impact

DDT is a Persistent Organic Pollutant and very highly persistent in the environment. It has a reported half life of between 2-15 years and is immobile in most soils. Its half life is 56 days in lake water and approximately 28 days in river water. 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.

Related Topics:
Persistent Organic Pollutant - Half life - Biodegradation

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In the States, human blood and fat tissue samples collected in the early 1970s showed detectable levels in all samples. A later study of blood samples collected in the latter half of the 1970s showed that blood levels were declining further, but DDT or metabolites were still seen in a very high proportion of the samples.

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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.

Related Topics:
Organochlorine - Estrogen - Mouse - Rat - Epidemiological

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DDT and its metabolic products accumulate through the food chain, with apex predators such as raptors having a higher concentration of the chemicals than other animals sharing the same environment. In particular, DDT has been cited as a major reason for the decline of the bald eagle in the 1950s and 1960s. In general, however, DDT in small quantities has very little effect on birds; its primary metabolite, DDE, has a much greater impact. DDT and DDE have had little impact on some birds which are not apex predators, like the chicken.

Related Topics:
Apex predator - Bald eagle

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DDT is very highly toxic to aquatic life, including crayfish, daphnids, sea shrimp and many species of fish. DDT may be moderately toxic to some amphibian species, especially in the larval stages. In addition to acute toxic effects, DDT may bioaccumulate significantly in fish and other aquatic species, leading to long-term exposure.

Related Topics:
Crayfish - Daphnids - Sea shrimp - Fish - Amphibian

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DDT is not particularly toxic to humans, compared to other widely used pesticides. In particular, no link to cancer has yet been established. Numerous studies have been conducted, including one in which humans voluntarily ingested 35 mg of DDT daily for almost two years. DDT is often applied directly to clothes and used in soap, with no demonstrated ill effects.

Related Topics:
Toxic - Human

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Some chemical and pesticide proponents claim there is not a single known human death from DDT poisoning. However, a study (Haun & Cueto, 1967) states, "In a 9-month-old child, poisoned with a 2:1 mixture of camphechlor and DDT, death occurred after convulsions and

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respiratory failure." Studies into organochlorines indicate "a dose of approximately 10 mg/kg leads to convulsions. An oral median lethal dose (LD50) is higher than 50 mg/kg in animal studies."

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