Chlordane

Chlordane, or chlordan, is an organochlorine compound used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was banned 10 years earlier for food crops like corn and citrus, and on lawns and domestic gardens.cis-chlordane (also known as α-chlordane (CAS=5103-71-9))trans-chlordane (also known as γ-chlordane and beta-chlordane (CAS=5103-74-2))trans-nonachlor(+)-heptachlor Chlordane, or chlordan, is an organochlorine compound used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was banned 10 years earlier for food crops like corn and citrus, and on lawns and domestic gardens. Like other chlorinated cyclodiene insecticides, chlordane is classified as an organic pollutant hazardous for human health. It is resistant to degradation in the environment and in humans/animals and readily accumulates in lipids (fats) of humans and animals. Exposure to the compound has been linked to cancers and many other diseases. Technical chlordane development was by chance by Julius Hyman in 1948, during a search for possible uses of a by-product of synthetic rubber manufacturing. By chlorinating this by-product, persistent and potent insecticides were easily and cheaply produced. The chlorine atoms, 7 in the case of heptachlor and 8 in chlordane, and 9 in the case of nonachlor, surround and stabilize the cyclodiene ring and thus these compounds are referred to as cyclodienes. Other members of the cyclodiene family of organochorine insecticides are aldrin and its epoxide, dieldrin, as well as endrin, which is a stereoisomer of dieldrin. Cyclodiene derives its name from hexachlorocyclopentadiene a precursor in its production. Hexachlorocyclopentadiene forms a Diels-Alder adduct with cyclopentadiene to give Chlordene intermediate ; chlorination of this adduct gives predominantly two chlordane isomers, α and β, in addition to other products such as trans-nonachlor and heptachlor. The β-isomer is popularly known as gamma and is more bioactive. The mixture that is composed of 147 components is called technical chlordane. Chlordane appears as a white or off-white crystals when synthesized, but it was more commonly sold in various formulations as oil solutions, emulsions, sprays, dusts, and powders. These products were sold in the United States from 1948 to 1988. Because of concern for harm to human health and to the environment, the United States Environmental Protection Agency (EPA) banned all uses of chlordane in 1983, except termite control in wooden structures (e.g. houses). After many reports of chlordane in the indoor air of treated homes, EPA banned the remaining use of chlordane in 1988. The EPA recommends that children should not drink water with more than 60 parts of chlordane per billion parts of drinking water (60 ppb) for longer than 1 day. EPA has set a limit in drinking water of 2 ppb. Chlordane is very persistent in the environment because it does not break down easily. Tests of the air in the residence of U.S. government housing, 32 years after chlordane treatment, showed levels of chlordane and heptachlor 10-15 times the Minimal Risk Levels (20 nanograms/cubic meter of air) published by the Centers for Disease Control. It has an environmental half-life of 10 to 20 years. In the years 1948–1988 chlordane was a common pesticide for corn and citrus crops, as well as a method of home termite control. Pathways of exposure to chlordane include ingestion of crops grown in chlordane-contaminated soil, inhalation of air in chlordane-treated homes and from landfills, and ingestion of high-fat foods such as meat, fish, and dairy, as chlordane builds up in fatty tissue. The United States Environmental Protection Agency reported that over 30 million homes were treated with technical chlordane or technical chlordane with heptachlor. Depending on the site of home treatment, the indoor air levels of chlordane can still exceed the Minimal Risks Levels (MRLs) for both cancer and chronic disease by orders of magnitude. Chlordane is excreted slowly through feces, urine elimination, and through breast milk in nursing mothers. It is able to cross the placenta and become absorbed by developing fetuses in pregnant women. A breakdown product of chlordane, the metabolite oxychlordane, accumulates in blood and adipose tissue with age. Being hydrophobic, chlordane adheres to soil particles and enters groundwater only slowly, owing to its low solubility (0.009 ppm). It requires many years to degrade. Chlordane bioaccumulates in animals. It is highly toxic to fish, with an LD50 of 0.022–0.095 mg/kg (oral).