Chlordane, or chlordan, is an organochlorine compound that was used as a

pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and ...

. 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 Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The ...

and

citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...

, and on lawns and domestic gardens.Robert L. Metcalf "Insect Control" in ''Ullmann’s Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim, 2002. Like other chlorinated

cyclodiene Hexachlorocyclopentadiene (HCCPD), also known as C-56, Graphlox, and HRS 1655, is an organochlorine compound with the formula C5Cl6. It is a precursor to pesticides, flame retardants, and dyes. It is a colourless liquid, although commercial sam ...

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.Agency for Toxic Substances & Disease Registry (ATSDR). Toxic Substances Portal: Chlordane. Last updated September, 2010 nline Available at URL: http://www.atsdr.cdc.gov/substances/toxsubstance.asp?toxid=62 Exposure to the compound has been linked to

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

s, diabetes, and neurological disorders.

Production, composition and uses

Technical chlordane development was by chance at Velsicol Chemical Corporation by Julius Hyman in 1948, during a search for possible uses of a by-product of

synthetic rubber A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubb ...

manufacturing. By chlorinating this by-product, persistent and potent insecticides were easily and cheaply produced. The chlorine atoms, 7 in the case of heptachlor, 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 organochlorine insecticides are

aldrin Aldrin is an organochlorine insecticide that was widely used until the 1990s, when it was banned in most countries. Aldrin is a member of the so-called "classic organochlorines" (COC) group of pesticides. COCs enjoyed a very sharp rise in popular ...

and its epoxide,

dieldrin Dieldrin is an organochloride originally produced in 1948 by J. Hyman & Co, Denver, as an insecticide. Dieldrin is closely related to aldrin, which reacts further to form dieldrin. Aldrin is not toxic to insects; it is oxidized in the insect to ...

, as well as

endrin Endrin is an organochloride with the chemical formula C12H8Cl6O that was first produced in 1950 by Shell and Velsicol Chemical Corporation. It was primarily used as an insecticide, as well as a rodenticide and piscicide. It is a colourless, odo ...

, which is a stereoisomer of dieldrin. Cyclodiene derives its name from hexachlorocyclopentadiene, a precursor in its production. Synthese Chlordan

Hexachlorocyclopentadiene forms a Diels-Alder

adduct An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...

with

cyclopentadiene Cyclopentadiene is an organic compound with the formula C5H6.LeRoy H. Scharpen and Victor W. Laurie (1965): "Structure of cyclopentadiene". ''The Journal of Chemical Physics'', volume 43, issue 8, pages 2765-2766. It is often abbreviated CpH beca ...

to give chlordene intermediate 734-48-3 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. Cis-chlordane.svg, ''cis''-chlordane (also known as α-chlordane (CAS=5103-71-9)) Trans-chlordane.svg, ''trans''-chlordane (also known as γ-chlordane and gamma-chlordane (CAS=5103-74-2)) Trans-nonachlor.svg, ''trans''-nonachlor (+)-Heptachlor.svg, (+)-heptachlor 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 The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

from 1948 to 1988. Because of concern for harm to human health and to the environment, the

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it ...

(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.

Origin, pathways of exposure, and processes of excretion

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.Agency for Toxic Substances & Disease Registry (ATSDR). ToxFaqs: September, 1995. Available at URL: http://www.atsdr.cdc.gov/toxfaqs/tfacts31.pdf 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.Center for Disease Control and Prevention (CDC). National Report on Human Exposure to Environmental Chemicals: Chemical Information: Chlordane. Last updated November, 2010 nline A breakdown product of chlordane, the metabolite oxychlordane, accumulates in blood and adipose tissue with age.

Environmental impact

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 of 0.022–0.095 mg/kg (oral). Oxychlordane (C₁₀H₄Cl₈O), the primary

metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, ...

of chlordane, and heptachlor epoxide, the primary

of heptachlor, along with the two other main components of the chlordane mixture, ''cis''-nonachlor and ''trans''-nonachlor, are the main bioaccumulating constituents. ''trans''-Nonachlor is more toxic than technical chlordane and ''cis''-nonachlor is less toxic. Chlordane and heptachlor are known as persistent organic pollutants (POP), classified among the "dirty dozen" and banned by the 2001

Stockholm Convention on Persistent Organic Pollutants Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed on 22 May 2001 in Stockholm and effective from 17 May 2004, that aims to eliminate or restrict the production and use of persistent organi ...

Health effects

Exposure to chlordane/heptachlor and/or its metabolites (oxychlordane, heptachlor epoxide) are risk factors for type-2 diabetes, for lymphoma, for prostate cancer, for obesity, for testicular cancer, for breast cancer. An epidemiological study conducted by the National Cancer Institute reported that higher levels of chlordane in dust on the floors of homes were associated with higher rates of non-Hodgkin lymphoma in occupants. Breathing chlordane in indoor air is the main route of exposure for these levels in human tissues. Currently, EPA has defined a concentration of 24 nanogram per cubic meter of air (ng/M³) for chlordane compounds over a 20-year exposure period as the concentration that will increase the probability of cancer by 1 in 1,000,000 persons. This probability of developing cancer increases to 10 in 1,000,000 persons with an exposure of 100 ng/m³ and 100 in 1,000,000 with an exposure of 1000 ng/m³. The non-cancer health effects of chlordane compounds, which include diabetes, insulin resistance, migraines, respiratory infections, immune-system activation, anxiety, depression, blurry vision, confusion, intractable seizures as well as permanent neurological damage, probably affects more people than cancer. Trans-nonachlor and oxychlordane in serum of mothers during gestation has been linked with behaviors associated with autism in offspring at age 4–5. The

Agency for Toxic Substances and Disease Registry The Agency for Toxic Substances and Disease Registry (ATSDR) is a federal public health agency within the United States Department of Health and Human Services. The agency focuses on minimizing human health risks associated with exposure to haz ...

(ATSDR) has defined a concentration of chlordane compounds of 20 ng/m³ as the Minimal Risk Level (MRLs). ATSDR defines Minimal Risk Level as an estimate of daily human exposure to a dose of a chemical that is likely to be without an appreciable risk of adverse non-cancerous effects over a specific duration of exposure.ATSDR - Redirect - Toxicological Profile: Chlordane
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Remediation

Chlordane was applied under the home/building during treatment for termites and the half-life can be up to 30 years. Chlordane has a low vapor pressure and volatilizes slowly into the air of home/building above. To remove chlordane from indoor air requires either ventilation (Heat Exchange Ventilation) or activated carbon filtration. Chemical remediation of chlordane in soils was attempted by the US Army Corps of Engineers by mixing chlordane with aqueous lime and persulfate. In a

phytoremediation Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronom ...

study,

Kentucky bluegrass ''Poa pratensis'', commonly known as Kentucky bluegrass (or blue grass), smooth meadow-grass, or common meadow-grass, is a perennial species of grass native to practically all of Europe, North Asia and the mountains of Algeria and Morocco. Altho ...

and

Perennial ryegrass ''Lolium perenne'', common name perennial ryegrass, English ryegrass, winter ryegrass, or ray grass, is a grass from the family Poaceae. It is native to Europe, Asia and northern Africa, but is widely cultivated and naturalised around the world. ...

were found to be minimally affected by chlordane, and both were found to take it up into their roots and shoots. Mycoremediation of chlordane in soil have found that contamination levels were reduced. The fungus '' Phanerochaete chrysosporium'' has been found to reduce concentrations of chlordane by 21% in water in 30 days and in solids in 60 days.

References

External links

Chlordane Technical Fact Sheet - National Pesticide Information Center

Chlordane General Fact Sheet - National Pesticide Information Center

* ttps://web.archive.org/web/20090605154349/http://www.atsdr.cdc.gov/tfacts31.html ATSDR - ToxFAQs: Chlordane
CDC - NIOSH Pocket Guide to Chemical Hazards - Chlordane
{{Authority control Obsolete pesticides Organochloride insecticides IARC Group 2B carcinogens Endocrine disruptors Persistent organic pollutants under the Stockholm Convention Persistent organic pollutants under the Convention on Long-Range Transboundary Air Pollution