PMEP Home PagePesticide Active Ingredient InformationEXTOXNET: The Extension Toxicology NetworkCarbaryl to DicrotophosCypermethrin E X T O X N E T Extension Toxicology Network A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program. Pesticide Information Profile Cypermethrin Publication Date: 9/93 TRADE OR OTHER NAMESSome trade names include Ammo, Arrivo, Barricade, Basathrin, CCN52,Cymbush, Cymperator, Cynoff, Cypercopal, Cyperguard 25EC, Cyperhard Tech,Cyperkill, Cypermar, Demon, Flectron, Fligene CI, Folcord, Kafil, NRDC 149,Polytrin, PP383, Ripcord, Siperin, Stockade and Super.REGULATORY STATUSSome or all products containing cypermethrin may be classified asRestricted Use Pesticides (RUP) by the EPA (1) because of cypermethrin'stoxicity to fish (9). Restricted Use Pesticides may be purchased and usedonly by certified applicators. Pesticides containing cypermethrin must bearthe signal word "Danger" or "Caution" on the product label, depending on thecontent of the particular formulation (1).INTRODUCTIONCypermethrin is a synthetic pyrethroid insecticide used to control manypests, including moth pests of cotton, fruit and vegetable crops (1). It isalso used for crack, crevice and spot treatment for control of insect pests instores, warehouses, industrial buildings, houses, apartment buildings,greenhouses, laboratories and on ships, railcars, buses, trucks and aircraft.It may also be used in non-food areas in schools, nursing homes, hospitals,restaurants, hotels, and in food processing plants and as a barrier treatmentinsect repellent for horses (9). Cypermethrin is available in emulsifiableconcentrate, ULV, and wettable powder formulations (1). Technicalcypermethrin is a mixture of eight different isomers, each of which may haveits own chemical and biological properties.TOXICOLOGICAL EFFECTSACUTE TOXICITYCypermethrin is a moderately toxic material by dermal absorption oringestion (1, 3). It may cause irritation to the skin and eyes. Symptoms ofdermal exposure include numbness, tingling, itching, burning sensation, lossof bladder control, incoordination, seizures and possible death (3).Pyrethroids may adversely effect the central nervous system (3). Humanvolunteers given dermal doses of 130 ug/cm2 on the earlobe experienced localtingling and burning sensations (2). One man died after eating a mealcooked in a 10% cypermethrin concentrate that was mistakenly used for cookingoil. Shortly after the meal, the victim experienced nausea, prolongedvomiting, stomach pains, and diarrhea which progressed to convulsions,unconsciousness and coma. Other family members exhibited milder symptoms andsurvived after hospital treatment (2). Rats fed high doses of 37.5 mg/kg ofthe cis-isomer of cypermethrin for 5 weeks exhibited severe motorincoordination, while 20-30% of rats fed 85 mg/kg died 4 to 17 days aftertreatment began (2). Cypermethrin is not a skin or eye irritant, but itmay cause allergic skin reactions (9).The amount of a chemical that is lethal to one-half (50%) of experimentalanimals fed the material is referred to as its acute oral lethal dose fifty,or LD50. The oral LD50 for cypermethrin in rats is 250 mg/kg (in corn oil) or4,123 mg/kg (in water) (1). EPA reports an oral LD50 of 187 to 326 mg/kg inmale rats and 150 to 500 mg/kg in female rats (9). The oral LD50 also variesfrom 367 to 2,000 mg/kg in female rats, and from 82 to 779 mg/kg in mice,depending on the ratio of cis/trans-isomers present (2). This widevariation in toxicity may reflect different mixtures of isomers in thematerials tested. The oral LD50 reported in rabbits is 3,000 mg/kg (3).The dermal LD50 in rats is 1,600 mg/kg (3), and in rabbits is > 2,000 mg/kg(1) or > 4,800 mg/kg (2).CHRONIC TOXICITYLong-term exposure to cypermethrin may cause liver changes. Pathologicalchanges in the cortex of the thymus, liver, adrenal glands, lungs and skinwere observed in rabbits repeatedly fed cypermethrin (3).Reproductive EffectsNo adverse effects on reproduction were observed in a 3-generationstudy with rats given doses of 37.5 mg/kg, the highest dose tested (9).Teratogenic EffectsFAO has reported that cypermethrin is not teratogenic (2). No birthdefects were observed in the offspring of rats given doses as high as 70mg/kg/day nor in the offspring of rabbits given doses as high as 30mg/kg/day (9).Mutagenic EffectsFAO has reported that cypermethrin is not mutagenic, but tests with veryhigh doses on mice caused a temporary increase in the number of bone marrowcells with micronuclei. Other tests for mutagenic effects in human, bacterialand hamster cell cultures and in live mice have been negative (2).Carcinogenic EffectsEPA has classified cypermethrin as a weak possible human carcinogenbecause there is some evidence that it caused benign lung tumors in only onesex and one species (female mice) tested, and then only at the highest dosetested (1,600 ppm). No tumors occurred in rats given doses of up to 75 mg/kg(9).Organ ToxicityPyrethroids may cause adverse effects on the central nervous system.Long-term feeding studies have caused increased liver and kidney weights andadverse changes to liver tissues in test animals (3).Fate in Humans and AnimalsIn humans, urinary excretion of cypermethrin metabolites was complete 48hours after the last of 5 daily doses of 1.5 mg (2). Studies in rats haveshown that cypermethrin is rapidly metabolized by hydroxylation and cleavage,with over 99% being eliminated within hours. The remaining 1% becomessequestered in body fat. This portion is eliminated slowly, with ahalf-life of 18 days for the cis-isomer and 3.4 days for thetrans-isomer (2, 4).ECOLOGICAL EFFECTSEffects on BirdsCypermethrin is practically non-toxic to birds. Its acute oral LD50 inmallard ducks is > 4,640 mg/kg (9). The dietary LC50 for mallards andbobwhite quail is > 20,000 ppm (9). No adverse reproductive effectsoccurredin mallards or bobwhite quail given 50 ppm, the highest dose tested (9).Effects on Aquatic OrganismsCypermethrin is extremely toxic to fish and aquatic invertebrates. The96-hour LC50 for cypermethrin in rainbow trout is 0.82 ppb, and in bluegillsunfish is 1.78 ppb. Its acute LC50 for Daphnia magna, a small freshwatercrustacean, is 0.2 ppb. The bioconcentration factor for cypermethrin inrainbow trout was 1200 times in a flow through study (9).Cypermethrin is metabolized and eliminated significantly more slowly byrainbow trout than by mammals or birds (11), which may explain thiscompound's higher toxicity in fish than in other organisms.The pyrethroid insecticides are extremely toxic to fish with 96-hourLC50 values generally below 10 ug/l. Corresponding LD50 values in mammals andbirds are in the range of several hundred to several thousand mg/kg. Fishsensitivity to the pyrethroids may be explained by their relatively slowmetabolism and elimination of these compounds. The half-lives for eliminationof several pyrethroids by trout are all greater than 48 hours, whileelimination half-lives for birds and mammals range from 6 to 12 hours (15).Generally, the lethality of pyrethroids to fish increases withincreasing octanol/water partition coefficients (16).Effects on Other Animals (Nontarget species)Cypermethrin is highly toxic to bees (8, 9).ENVIRONMENTAL FATEBreakdown of Chemical in Soil and GroundwaterCypermethrin is not soluble in water and has a strong tendency toadsorb to soil particles. It is therefore unlikely to cause groundwatercontamination (5, 9).On soils, cypermethrin photodegrades rapidly with a half-life of 8 to 16days. Its major photodegradation products are DCVA, 3-phenoxybenzaldehyde,and 3-phenoxybenzoic acid. Cypermethrin is also subject to microbialdegradation under aerobic conditions (9).Under laboratory conditions, cypermethrin degrades more rapidly on sandyclay and sandy loam soils than on clay soils and more rapidly in soils lowin organic material (9). In aerobic conditions, its soil half-life is 2to 8 weeks. Cypermethrin is more persistent under anaerobic conditions (9).Its soil half-life is 63 days (5) or, under field conditions, 4 to 12days (9). When applied to a sandy soil under laboratory conditions, its half-life was 2.5 weeks and declined to 6% of the amount applied within 48 weeks(6). When applied to soil at 125 g of active ingredient per ha, residues ofcypermethrin were detectable 15 days later, but were not detectable 30 daysafter the application (7).Breakdown of Chemical in Surface WaterIn neutral or acid aqueous solution, cypermethrin hydrolyzes slowly, withhydrolysis being more rapid at pH 9. Slow photodegradation occurred in asterile solution exposed to sunlight (< 10% in 32 days). Under normalenvironmental temperatures and pH, cypermethrin is stable to hydrolysis with ahalf-life of > 50 days and to photodegradation with a half-life of > 100 days(9).When applied to open water at 125 g of active ingredient per ha, theconcentration of cypermethrin in the water dropped by 95% within 24 hours (7).This rapid loss was probably due to adsorption of cypermethrin to sedimentand suspended soil particles (10). The remaining residues persisted for30 days when measurements were ceased (7).In pond waters and in laboratory degradation studies, pyrethroidconcentrations decrease rapidly due to sorption to sediment, suspendedparticles and plants. Microbial and photodegradation also occur.Breakdown of Chemical in VegetationWhen a 4.5 ml/100 l solution of Cymbush 250 EC was applied to strawberryplants until run-off, 40% of the applied cypermethrin remained after 1 day,12% remained after 3 days, and 0.5% remained after 7 days, with a light rainoccurring on day 3 (12).When cypermethrin was applied to wheat at 28 g of active ingredient/ ha,residues on the wheat were 4 ppm immediately after spraying and declined to0.2 ppm 27 days later. No cypermethrin was detected in the grain. Similarresidue loss patterns have been observed on treated lettuce and celery crops.In another study with cypermethrin applied to wheat at 0.25 to 1.5 kg/ha, itshalf-life was 4.8 days (13).PHYSICAL PROPERTIES AND GUIDELINESPure isomers of cypermethrin form colorless crystals. When mixedisomers are present, cypermethrin is a viscous semi-solid (1) or aviscous, yellow liquid (2). Cypermethrin is light stable (2).Workers handling products containing cypermethrin should wear protectiveclothing as directed on the product label.Cypermethrin may pose a slight fire hazard if exposed to heat or flame.It may burn, but does not readily ignite. Avoid contact with strongoxidizers, excessive heat, sparks and open flame. Thermal decomposition mayrelease toxic fumes of hydrogen cyanide, chlorine, and oxides of nitrogen andcarbon (3).Exposure Guidelines:No occupational exposure limits have been established for cypermethrin byOSHA, NIOSH or ACGIH (3).ADI: 0.01 mg/kg/day based on a dog study with a NOEL of 1.0 mg/kg/day and a 100 fold safety margin (9).MPI: 0.60 mg/kg/day for a 60 kg person (9).Physical Properties:CAS #: 52315-07-8Chemical Name: (R,S)-alpha-Cyano-3-phenoxybenzyl-2,2-dimethyl (1R, 1S)-cis,trans-3-(2,2-dichlorovinyl) cyclopropane-carboxylateChemical Class/Use: Synthetic pyrethroid insecticideDensity: 1.12 gm/ml at 22 degrees C (2); 1.249 g/cm3 at 20 degrees C (9).H20 solubility: insoluble in water (1); 9 ug/liter (2)Solubility in other solvents: soluble in methanol, acetone, xylene, methylene dichloride (1)Melting point: 60-80 degrees C (pure isomers) (1, 2); 177 degrees F (81 degrees C)(3).Boiling point: 170-195 degrees C (9)Flashpoint: > 572 degrees F (> 300 degrees C) (3)Vapor pressure: 4 x 10-8 mm Hg at 70 degrees C (2); 1.3 x 10-3 mm Hg at 20 degrees C (3); 8 x 10-4 mm Hg at 80 degrees C and 1 x 10-7 mm Hg at 20 degrees C (9).Koc: 160,000 gm/ml (5)BASIC MANUFACTURERBASF Corp.Agricultural Products GroupPO Box 135282505 Meridian Pkwy.Research Triangle Park 27709-3528Review by Basic Manufacturer - BASF Corp.:Comments solicited: April, 1993Comments received:Zeneca Ag ProductsWilmington DE 19897Telephone: 800-759-4500Review by Basic Manufacturer - Zeneca:Comments solicited: April, 1993Comments received:REFERENCES Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. MeisterPublishing Company, Willoughby, OH. Hayes, W.J. and E.R. Laws (ed.). 1990. Handbook of PesticideToxicology, Classes of Pesticides, Vol. 3. Academic Press, Inc., NY Occupational Health Services, Inc. 1993 (Nov. 17). MSDS forCypermethrin. OHS Inc., Secaucus, NJ. National Coalition Against the Misuse of Pesticides. October 1989.Chemical Watch Fact Sheet: Cypermethrin. NCAMP, Washington, DC. U. S. Department of Agriculture, Soil Conservation Service. 1990(Nov.). SCS/ARS/CES Pesticide Properties Database: Version 2.0(Summary). USDA - Soil Conservation Service, Syracuse, NY. Harris, C.R. et al. 1981. Laboratory studies on the persistenceandbehavior in soil of four pyrethroid insecticides. Canadian Entomologist113: 685-94. Agnihotri, N.P. et al. 1986. Persistence of some syntheticpyrethroid insecticides in soil, water and sediment, Part I. J. Ent.Res. 10 (2): 147-51. Waller, G.D. et al. 1988. Pyrethroid residues and toxicity tohoneybees of selected pyrethroid formulations applied to cotton inArizona. J. of Economic Entomology 81 (4): 1022-6. U.S. Environmental Protection Agency. Jan. 3, 1989. Pesticide FactSheet Number 199: Cypermethrin. US EPA, Office of Pesticide Programs,Registration Div., Washington, DC. Muir, D.C.G., et al. 1985. Bioconcentration of cypermethrin,deltamethrin, fenvalerate and permethrin by Chironomus tentans larvae insediment and water. Environmental Toxicology and Chemistry 4: 51-61. Bradbury, S.P. and J.R. Coats. 1989. Toxicokinetics andtoxicodynamics of pyrethroid insecticides in fish. EnvironmentalToxicology and Chemistry 8: 373-380. Belanger, A. et al. 1990. A field study of four insecticides usedin strawberry protection. J. of Environmental Science and health, Part B25 (5): 615-25. Westcott, N.D. and R.A. Reichle. 1987. Persistence of deltamethrinand cypermethrin on wheat and sweet clover. J. of Environmental Scienceand health, Part B 22 (1): 91-101. Muir, D.C.G., et al. 1985. Bioconcentration of cypermethrin,deltamethrin, fenvalerate and permethrin by Chironomus tentans larvae insediment and water. Environmental Toxicology and Chemistry 4: 51-61. Bradbury, S.P. and J.R. Coats. 1989. Toxicokinetics andtoxicodynamics of pyrethroid insecticides in fish. EnvironmentalToxicology and Chemistry 8: 373-380. Haya, K. 1989. Toxicity of pyrethroid insecticides to fish.Environmental Toxicology and Chemistry 8: 381-391.
