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Chlordane is an organochlorine insecticide, more specifically a chlorinated cyclic hydrocarbon within the cyclodiene group. The proper scientific name for chlordane is 1,2,4,5,6,7,8,8-Octachloro-3a,4,7,7a-tetrahydro-4,7-methanoindan. However, the actual technical product is a mixture of various chlorinated hydrocarbons, including isomers of chlordane and other closely related compounds.

The first usage of chlordane as an insecticide was in 1945. Its use was widespread up until the 1970s and included applications inside of homes to control insects of stored food and clothing, as well as usage to control termites, carpenter ants, and wood-boring beetles. An especially intensive use was to kill earthworms in golf-course putting greens and in prize lawns, for which more than 9 kg/ha might be applied. The major use of chlordane in agriculture was for the control of insect pests in soil and on plants. In 1971 about 25 million lb (11.4 million kg) of chlordane was manufactured in the United States, of which about 8% was used in agriculture, and most of the rest in and around homes. Today the use of chlordane is highly restricted, and limited to the control of fire ants.

Like other chlorinated hydrocarbon insecticides such as DDT, chlordane is virtually insoluble in water (5 ppm), but highly soluble in organic solvents and oils. This property, coupled with the persistence of chlordane in the environment, gives it a propensity to accumulate in organisms (i.e., to bioaccumulate), especially in animals at the top of food webs. Because of its insolubility in water, chlordane is relatively immobile in soil, and tends not to leach into surface or ground water.

The acute toxicity of chlordane to humans is considered to be high to medium by oral ingestion, and hazardous by inhalation. Chlordane causes damage to many organs, including the liver, testicles, blood, and the neural system. It also affects hormone levels and is a suspected mutagen and carcinogen. Chlordane is very toxic to arthropods and to some fish, birds, and mammals.

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