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Cypermethrin
Cypermethrin SA Burr, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, UK Ó 2014 Elsevier Inc. All rights reserved. This article is a revision of the previous edition article by Paul R. Harp, volume 1, pp 714–716, Ó 2005, Elsevier Inc. l l
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Chemical Abstracts Service Registry Number: CAS 52315-07-8 Synonyms: [Cyano-(3-phenoxyphenyl)methyl] 3-(2,2dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate; Ammo; Asymmethrin; Barricade; Cymperator; Cypercopal; Cypermethrine; Hilcyperin; Neramethrin; Ripcord; CID 2912 Classification: Type II pyrethroid insecticide Molecular Formula: C22H19Cl2NO3, molecular weight 416.29716 Chemical Structure:
rapidly metabolized through ester cleavage and hydroxylation. Pyrethroids accumulate in adipose tissue, which has a varying affinity for the different isomeric forms of cypermethrin. In rat, elimination half-lives of 3.4 and 18 days have been measured for trans and cis isomers, respectively. Urinary excretion is the primary route of elimination. Fecal excretion can also be significant depending on the animal species and isomeric form.
Mechanism of Toxicity Cypermethrin is a type II pyrethroid: a functional neurotoxin slowing the inactivation of voltage-gated sodium channels leading to a state of hyperexcitability, which in turn causes fine tremor, salivation, and choreoathetosis. Other proposed contributory actions include antagonism of g-aminobutyric acid A (GABAA) inhibition, and voltage-gated chloride and calcium channels.
Acute and Short-Term Toxicity Cypermethrin produces a syndrome in both insects and mammals known as chorea salivation. The effects are hyperexcitability, fine tremor, hypersalivation, choreoathetosis, ataxia, seizures, and death. Humans experience the same effects as other animals, but are also able to report paresthesia after dermal exposure and nausea after ingestion.
Uses Cypermethrin is a potent broad-spectrum insecticide used in a range of agricultural, public health, and domestic applications. For arable farming, cypermethrin is one of the most widely used pesticides in terms of total land area treated. Cypermethrin is available as a powder, emulsion, or a concentrate for ultra-low-volume application. Technical cypermethrin is a mixture of eight isomers that includes two active isomers (1R cis S and 1S cis R isomers).
Chronic Toxicity, Genotoxicity, and Carcinogenicity Studies of mice have demonstrated possible genotoxicity in spleen and bone marrow. The US Environmental Protection Agency has classified cypermethrin as a possible human carcinogen based on benign lung adenomas found in mice. Chronic effects following cypermethrin exposure have not been reported in humans.
Environmental Fate Clinical Management Cypermethrin is sixfold more persistent in soil than in aquatic environments. Depending on conditions, the environmental half-life ranges from 2 days (for hydrolysis at pH 9) to 165 days (for photolysis in soil).
Exposure Dermal exposure is the most common route, although ingestion and inhalation can occur.
Toxicokinetics Absorption of pyrethroids is poor through the skin and not much more effective through the gastrointestinal tract. Pyrethroids are
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Dermal exposure can be treated by washing the contaminated skin with oils. Application of vitamin E cream preparations can be used for both prophylaxis and treatment of paresthesia. With cases of ingestion, gastric decontamination with activated charcoal may be of benefit within the first hour. Gastric lavage should be avoided when formulations contain solvents. If systemic toxicity does occur, the central signs of poisoning can be difficult to control and may be confused with intoxication by other pesticides such as anticholinesterases, which also cause hyperexcitability, although pyrethroids do not inhibit acetylcholinesterase. Respiratory support may be needed and control of metabolic acidosis may require sodium bicarbonate. Atropine may be useful to control
Encyclopedia of Toxicology, Volume 1
http://dx.doi.org/10.1016/B978-0-12-386454-3.00120-2
Cypermethrin
hypersalivation. Single short-lived seizures may not require treatment. Since pyrethroids do not produce morphological damage, only symptomatic treatment is needed. Frequent or prolonged convulsions may be controlled with intravenous diazepam or lorazepam. If unresponsive, consider phenobarbital or phenytoin (before thiopental or general anesthesia). Pentobarbitone has been shown to be more effective than phenobarbitone in animal studies. Complete recovery usually occurs following symptomatic treatment in cases of mild– moderate intoxication.
Ecotoxicology Birds have a comparatively low susceptibility to cypermethrin, whereas bees, crustaceans, and fish are all highly susceptible under experimental conditions. However, environmental factors such as sediment binding may reduce the actual susceptibility of nontarget aquatic species.
Exposure Standards and Guidelines The acceptable daily intake set by the Food and Agriculture Organization (FAO)/World Health Organization (WHO) Joint
1121
Meeting on Pesticide Residues (JMPR) for cypermethrin is 0–0.02 mg kg 1 body weight.
See also: Cyfluthrin; Deltamethrin; Neurotoxicity; Permethrin; Pesticides; Pyrethrins/Pyrethroids.
Further Reading WHO/IPCS, 1989. Environmental Health Criteria 82: Cypermethrin. World Health Organization, Geneva.
Relevant Websites http://toxnet.nlm.nih.gov – TOXNET, Toxicology Data Network, National Library of Medicine, Search for Cypermethrin. http://www.who.int – World Health Organization, Search for Cypermethrin.
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Chemical Abstracts Service Registry Number: CAS 52315-07-8 Synonyms: [Cyano-(3-phenoxyphenyl)methyl] 3-(2,2dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate; Ammo; Asymmethrin; Barricade; Cymperator; Cypercopal; Cypermethrine; Hilcyperin; Neramethrin; Ripcord; CID 2912 Classification: Type II pyrethroid insecticide Molecular Formula: C22H19Cl2NO3, molecular weight 416.29716 Chemical Structure:
rapidly metabolized through ester cleavage and hydroxylation. Pyrethroids accumulate in adipose tissue, which has a varying affinity for the different isomeric forms of cypermethrin. In rat, elimination half-lives of 3.4 and 18 days have been measured for trans and cis isomers, respectively. Urinary excretion is the primary route of elimination. Fecal excretion can also be significant depending on the animal species and isomeric form.
Mechanism of Toxicity Cypermethrin is a type II pyrethroid: a functional neurotoxin slowing the inactivation of voltage-gated sodium channels leading to a state of hyperexcitability, which in turn causes fine tremor, salivation, and choreoathetosis. Other proposed contributory actions include antagonism of g-aminobutyric acid A (GABAA) inhibition, and voltage-gated chloride and calcium channels.
Acute and Short-Term Toxicity Cypermethrin produces a syndrome in both insects and mammals known as chorea salivation. The effects are hyperexcitability, fine tremor, hypersalivation, choreoathetosis, ataxia, seizures, and death. Humans experience the same effects as other animals, but are also able to report paresthesia after dermal exposure and nausea after ingestion.
Uses Cypermethrin is a potent broad-spectrum insecticide used in a range of agricultural, public health, and domestic applications. For arable farming, cypermethrin is one of the most widely used pesticides in terms of total land area treated. Cypermethrin is available as a powder, emulsion, or a concentrate for ultra-low-volume application. Technical cypermethrin is a mixture of eight isomers that includes two active isomers (1R cis S and 1S cis R isomers).
Chronic Toxicity, Genotoxicity, and Carcinogenicity Studies of mice have demonstrated possible genotoxicity in spleen and bone marrow. The US Environmental Protection Agency has classified cypermethrin as a possible human carcinogen based on benign lung adenomas found in mice. Chronic effects following cypermethrin exposure have not been reported in humans.
Environmental Fate Clinical Management Cypermethrin is sixfold more persistent in soil than in aquatic environments. Depending on conditions, the environmental half-life ranges from 2 days (for hydrolysis at pH 9) to 165 days (for photolysis in soil).
Exposure Dermal exposure is the most common route, although ingestion and inhalation can occur.
Toxicokinetics Absorption of pyrethroids is poor through the skin and not much more effective through the gastrointestinal tract. Pyrethroids are
1120
Dermal exposure can be treated by washing the contaminated skin with oils. Application of vitamin E cream preparations can be used for both prophylaxis and treatment of paresthesia. With cases of ingestion, gastric decontamination with activated charcoal may be of benefit within the first hour. Gastric lavage should be avoided when formulations contain solvents. If systemic toxicity does occur, the central signs of poisoning can be difficult to control and may be confused with intoxication by other pesticides such as anticholinesterases, which also cause hyperexcitability, although pyrethroids do not inhibit acetylcholinesterase. Respiratory support may be needed and control of metabolic acidosis may require sodium bicarbonate. Atropine may be useful to control
Encyclopedia of Toxicology, Volume 1
http://dx.doi.org/10.1016/B978-0-12-386454-3.00120-2
Cypermethrin
hypersalivation. Single short-lived seizures may not require treatment. Since pyrethroids do not produce morphological damage, only symptomatic treatment is needed. Frequent or prolonged convulsions may be controlled with intravenous diazepam or lorazepam. If unresponsive, consider phenobarbital or phenytoin (before thiopental or general anesthesia). Pentobarbitone has been shown to be more effective than phenobarbitone in animal studies. Complete recovery usually occurs following symptomatic treatment in cases of mild– moderate intoxication.
Ecotoxicology Birds have a comparatively low susceptibility to cypermethrin, whereas bees, crustaceans, and fish are all highly susceptible under experimental conditions. However, environmental factors such as sediment binding may reduce the actual susceptibility of nontarget aquatic species.
Exposure Standards and Guidelines The acceptable daily intake set by the Food and Agriculture Organization (FAO)/World Health Organization (WHO) Joint
1121
Meeting on Pesticide Residues (JMPR) for cypermethrin is 0–0.02 mg kg 1 body weight.
See also: Cyfluthrin; Deltamethrin; Neurotoxicity; Permethrin; Pesticides; Pyrethrins/Pyrethroids.
Further Reading WHO/IPCS, 1989. Environmental Health Criteria 82: Cypermethrin. World Health Organization, Geneva.
Relevant Websites http://toxnet.nlm.nih.gov – TOXNET, Toxicology Data Network, National Library of Medicine, Search for Cypermethrin. http://www.who.int – World Health Organization, Search for Cypermethrin.