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|Molar mass||416.30 g/mol|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cypermethrin is a synthetic pyrethroid used as an insecticide in large-scale commercial agricultural applications as well as in consumer products for domestic purposes. It behaves as a fast-acting neurotoxin in insects. It is easily degraded on soil and plants but can be effective for weeks when applied to indoor inert surfaces. Exposure to sunlight, water and oxygen will accelerate its decomposition. Cypermethrin is highly toxic to fish, bees and aquatic insects, according to the National Pesticides Telecommunications Network (NPTN). It is found in many household ant and cockroach killers, including Raid and ant chalk.
Excessive exposure can cause nausea, headache, muscle weakness, salivation, shortness of breath and seizures. In humans, cypermethrin is deactivated by enzymatic hydrolysis to several carboxylic acid metabolites, which are eliminated in the urine. Worker exposure to the chemical can be monitored by measurement of the urinary metabolites, while severe overdosage may be confirmed by quantitation of cypermethrin in blood or plasma.
Study in animals
A recent study at Xuzhou Medical College in China showed that, in male rats, cypermethrin can exhibit a toxic effect on the reproductive system. After 15 days of continual dosing, both androgen receptor levels and serum testosterone levels were significantly reduced. These data suggested that cypermethrin can induce impairments of the structure of seminiferous tubules and spermatogenesis in male rats at high doses.
Long-term exposure to cypermethrin during adulthood is found to induce dopaminergic neurodegeneration in rats, and postnatal exposure enhances the susceptibility of animals to dopaminergic neurodegeneration if rechallenged during adulthood.
If exposed to cypermethrin during pregnancy, rats give birth to offspring with developmental delays. In male rats exposed to cypermethrin, the proportion of abnormal sperm increases. It causes genetic damage: chromosomal abnormalities increased in bone marrow and spleen cells when mice were exposed to cypermethrin. Cypermethrin is classified as a possible human carcinogen, because it causes an increase in the frequency of lung tumors in female mice. Cypermethrin has been linked to an increase in bone marrow micronuclei in both mice and humans.
One study showed that cypermethrin inhibits “gap junctional intercellular communication”, which plays an important role in cell growth and is inhibited by carcinogenic agents. Studies have shown that residue from cypermethrin can last for 84 days in the air, on walls, the floor and on furniture.
Cypermethrin is a broad-spectrum insecticide, which means it kills beneficial insects and animals as well as the targeted insects. Fish are particularly susceptible to cypermethrin. Resistance to cypermethrin has developed quickly in insects exposed frequently and can render it ineffective.
- R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 389-391.
- Hu, JX; Li, YF; Li, J; Pan, C; He, Z; Dong, HY; Xu, LC (2011). "Toxic effects of cypermethrin on the male reproductive system: With emphasis on the androgen receptor". Journal of applied toxicology : JAT: n/a. doi:10.1002/jat.1769. PMID 22147539.
- Singh, AK; Tiwari, MN; Upadhyay, G; Patel, DK; Singh, D; Prakash, O; Singh, MP (2012). "Long term exposure to cypermethrin induces nigrostriatal dopaminergic neurodegeneration in adult rats: Postnatal exposure enhances the susceptibility during adulthood". Neurobiology of Aging 33 (2): 404–15. doi:10.1016/j.neurobiolaging.2010.02.018. PMID 20371137.
- Amer, S.M.; et al. (1993). "Induction of chromosomal aberrations and sister chromatid exchange in vivo and in vitro by the insecticide cypermethrin". Journal of Applied Toxicology 13 (5): 341–345. doi:10.1002/jat.2550130508. PMID 8258631.
- Amer, S.M. and E.I. Aboulela (1985). "Cytogenetic effects of pesticides. III. Induction of micronuclei in mouse bone marrow by the insecticides cypermethrin and rotenone". Journal of Mutation Research 155 (3): 135–142. doi:10.1016/0165-1218(85)90132-6.
- Tateno, C.; Ito, Seiichi; Tanaka, Mina; Yoshitake, Akira; et al. (1993). "Effects of pyrethroid insecticides on gap junctional intecellular communications in Balb/c3T3 cells by dye-transfer assay". Cell biology and toxicology journal 9 (3): 215–222. doi:10.1007/BF00755600.
- Wright, C.G., R.B. Leidy, and H.E. Dupree, Jr. (1993). "Cypermethrin in the ambient air and on surfaces of rooms treated for cockroaches". Bulletin of Environmental Contamination and Toxicology 51 (3): 356–360. doi:10.1007/BF00201752. PMID 8219589.
- Pascual, J.A. and S.J. Peris (1992). "Effects of forest spraying with two application rates of cypermethrin on food supply and on breeding success of the blue tit (Parus caeruleus)". Environmental Toxicology and Chemistry 11 (9): 1271–1280. doi:10.1002/etc.5620110907.
- Stephenson, R.R. (1982). "Aquatic toxicology of cypermethrin. I. Acute toxicity to some freshwater fish and invertebrates in laboratory tests". Aquatic Toxicology 2 (3): 175–185. doi:10.1016/0166-445X(82)90014-5.
- Martinez-Cabrillo, J.L.; et al. (1991). "Responses of populations of the tobacco budworm (Lepidopterea: Noctuidae) from northwest Mexico to pyrethroids". Journal of Economic Entomology 84 (2): 363–366.
- Cypermethrin Fact Sheet - National Pesticide Information Center
- Cypermethrin Pesticide Information Profile - Extension Toxicology Network
- Information on Cypermethrin from pesticideinfo.org 
- cypermethrin in the Pesticide Properties DataBase (PPDB)
- alpha-cypermethrin in the Pesticide Properties DataBase (PPDB)
- zeta-cypermethrin in the Pesticide Properties DataBase (PPDB)