E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
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University of California at Davis. Major support and funding was provided
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Pesticide
Information
Profile
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Cypermethrin
Publication Date: 9/93
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TRADE OR OTHER NAMES
Some 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 STATUS
Some or all products containing cypermethrin may be classified as
Restricted Use Pesticides (RUP) by the EPA (1) because of cypermethrin's
toxicity to fish (9). Restricted Use Pesticides may be purchased and used
only by certified applicators. Pesticides containing cypermethrin must bear
the signal word "Danger" or "Caution" on the product label, depending on the
content of the particular formulation (1).
INTRODUCTION
Cypermethrin is a synthetic pyrethroid insecticide used to control many
pests, including moth pests of cotton, fruit and vegetable crops (1). It is
also used for crack, crevice and spot treatment for control of insect pests in
stores, 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 treatment
insect repellent for horses (9). Cypermethrin is available in emulsifiable
concentrate, ULV, and wettable powder formulations (1). Technical
cypermethrin is a mixture of eight different isomers, each of which may have
its own chemical and biological properties.
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Cypermethrin is a moderately toxic material by dermal absorption or
ingestion (1, 3). It may cause irritation to the skin and eyes. Symptoms of
dermal exposure include numbness, tingling, itching, burning sensation, loss
of bladder control, incoordination, seizures and possible death (3).
Pyrethroids may adversely effect the central nervous system (3). Human
volunteers given dermal doses of 130 ug/cm2 on the earlobe experienced local
tingling and burning sensations (2). One man died after eating a meal
cooked in a 10% cypermethrin concentrate that was mistakenly used for cooking
oil. Shortly after the meal, the victim experienced nausea, prolonged
vomiting, stomach pains, and diarrhea which progressed to convulsions,
unconsciousness and coma. Other family members exhibited milder symptoms and
survived after hospital treatment (2). Rats fed high doses of 37.5 mg/kg of
the cis-isomer of cypermethrin for 5 weeks exhibited severe motor
incoordination, while 20-30% of rats fed 85 mg/kg died 4 to 17 days after
treatment began (2). Cypermethrin is not a skin or eye irritant, but it
may cause allergic skin reactions (9).
The amount of a chemical that is lethal to one-half (50%) of experimental
animals 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) or
4,123 mg/kg (in water) (1). EPA reports an oral LD50 of 187 to 326 mg/kg in
male rats and 150 to 500 mg/kg in female rats (9). The oral LD50 also varies
from 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 wide
variation in toxicity may reflect different mixtures of isomers in the
materials 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 TOXICITY
Long-term exposure to cypermethrin may cause liver changes. Pathological
changes in the cortex of the thymus, liver, adrenal glands, lungs and skin
were observed in rabbits repeatedly fed cypermethrin (3).
Reproductive Effects
No adverse effects on reproduction were observed in a 3-generation
study with rats given doses of 37.5 mg/kg, the highest dose tested (9).
Teratogenic Effects
FAO has reported that cypermethrin is not teratogenic (2). No birth
defects were observed in the offspring of rats given doses as high as 70
mg/kg/day nor in the offspring of rabbits given doses as high as 30
mg/kg/day (9).
Mutagenic Effects
FAO has reported that cypermethrin is not mutagenic, but tests with very
high doses on mice caused a temporary increase in the number of bone marrow
cells with micronuclei. Other tests for mutagenic effects in human, bacterial
and hamster cell cultures and in live mice have been negative (2).
Carcinogenic Effects
EPA has classified cypermethrin as a weak possible human carcinogen
because there is some evidence that it caused benign lung tumors in only one
sex and one species (female mice) tested, and then only at the highest dose
tested (1,600 ppm). No tumors occurred in rats given doses of up to 75 mg/kg
(9).
Organ Toxicity
Pyrethroids may cause adverse effects on the central nervous system.
Long-term feeding studies have caused increased liver and kidney weights and
adverse changes to liver tissues in test animals (3).
Fate in Humans and Animals
In humans, urinary excretion of cypermethrin metabolites was complete 48
hours after the last of 5 daily doses of 1.5 mg (2). Studies in rats have
shown that cypermethrin is rapidly metabolized by hydroxylation and cleavage,
with over 99% being eliminated within hours. The remaining 1% becomes
sequestered in body fat. This portion is eliminated slowly, with a
half-life of 18 days for the cis-isomer and 3.4 days for the
trans-isomer (2, 4).
ECOLOGICAL EFFECTS
Effects on Birds
Cypermethrin is practically non-toxic to birds. Its acute oral LD50 in
mallard ducks is > 4,640 mg/kg (9). The dietary LC50 for mallards and
bobwhite quail is > 20,000 ppm (9). No adverse reproductive effects
occurred
in mallards or bobwhite quail given 50 ppm, the highest dose tested (9).
Effects on Aquatic Organisms
Cypermethrin is extremely toxic to fish and aquatic invertebrates. The
96-hour LC50 for cypermethrin in rainbow trout is 0.82 ppb, and in bluegill
sunfish is 1.78 ppb. Its acute LC50 for Daphnia magna, a small freshwater
crustacean, is 0.2 ppb. The bioconcentration factor for cypermethrin in
rainbow trout was 1200 times in a flow through study (9).
Cypermethrin is metabolized and eliminated significantly more slowly by
rainbow trout than by mammals or birds (11), which may explain this
compound's higher toxicity in fish than in other organisms.
The pyrethroid insecticides are extremely toxic to fish with 96-hour
LC50 values generally below 10 ug/l. Corresponding LD50 values in mammals and
birds are in the range of several hundred to several thousand mg/kg. Fish
sensitivity to the pyrethroids may be explained by their relatively slow
metabolism and elimination of these compounds. The half-lives for elimination
of several pyrethroids by trout are all greater than 48 hours, while
elimination half-lives for birds and mammals range from 6 to 12 hours (15).
Generally, the lethality of pyrethroids to fish increases with
increasing octanol/water partition coefficients (16).
Effects on Other Animals (Nontarget species)
Cypermethrin is highly toxic to bees (8, 9).
ENVIRONMENTAL FATE
Breakdown of Chemical in Soil and Groundwater
Cypermethrin is not soluble in water and has a strong tendency to
adsorb to soil particles. It is therefore unlikely to cause groundwater
contamination (5, 9).
On soils, cypermethrin photodegrades rapidly with a half-life of 8 to 16
days. Its major photodegradation products are DCVA, 3-phenoxybenzaldehyde,
and 3-phenoxybenzoic acid. Cypermethrin is also subject to microbial
degradation under aerobic conditions (9).
Under laboratory conditions, cypermethrin degrades more rapidly on sandy
clay and sandy loam soils than on clay soils and more rapidly in soils low
in organic material (9). In aerobic conditions, its soil half-life is 2
to 8 weeks. Cypermethrin is more persistent under anaerobic conditions (9).
Its soil half-life is 63 days (5) or, under field conditions, 4 to 12
days (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 of
cypermethrin were detectable 15 days later, but were not detectable 30 days
after the application (7).
Breakdown of Chemical in Surface Water
In neutral or acid aqueous solution, cypermethrin hydrolyzes slowly, with
hydrolysis being more rapid at pH 9. Slow photodegradation occurred in a
sterile solution exposed to sunlight (< 10% in 32 days). Under normal
environmental temperatures and pH, cypermethrin is stable to hydrolysis with a
half-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, the
concentration of cypermethrin in the water dropped by 95% within 24 hours (7).
This rapid loss was probably due to adsorption of cypermethrin to sediment
and suspended soil particles (10). The remaining residues persisted for
30 days when measurements were ceased (7).
In pond waters and in laboratory degradation studies, pyrethroid
concentrations decrease rapidly due to sorption to sediment, suspended
particles and plants. Microbial and photodegradation also occur.
Breakdown of Chemical in Vegetation
When a 4.5 ml/100 l solution of Cymbush 250 EC was applied to strawberry
plants 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 rain
occurring 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 to
0.2 ppm 27 days later. No cypermethrin was detected in the grain. Similar
residue 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, its
half-life was 4.8 days (13).
PHYSICAL PROPERTIES AND GUIDELINES
Pure isomers of cypermethrin form colorless crystals. When mixed
isomers are present, cypermethrin is a viscous semi-solid (1) or a
viscous, yellow liquid (2). Cypermethrin is light stable (2).
Workers handling products containing cypermethrin should wear protective
clothing 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 strong
oxidizers, excessive heat, sparks and open flame. Thermal decomposition may
release toxic fumes of hydrogen cyanide, chlorine, and oxides of nitrogen and
carbon (3).
Exposure Guidelines:
No occupational exposure limits have been established for cypermethrin by
OSHA, 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 #: | 52315-07-8 |
| Chemical Name: | (R,S)-alpha-Cyano-3-phenoxybenzyl-2,2-dimethyl (1R, 1S)-cis,trans-3-(2,2-dichlorovinyl) cyclopropane-carboxylate |
| Chemical Class/Use: | Synthetic pyrethroid insecticide |
| Density: | 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 MANUFACTURER
BASF Corp.
Agricultural Products Group
PO Box 13528
2505 Meridian Pkwy.
Research Triangle Park 27709-3528
Review by Basic Manufacturer - BASF Corp.:
Comments solicited: April, 1993
Comments received:
Zeneca Ag Products
Wilmington DE 19897
Telephone: 800-759-4500
Review by Basic Manufacturer - Zeneca:
Comments solicited: April, 1993
Comments received:
REFERENCES
Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister
Publishing Company, Willoughby, OH.
Hayes, W.J. and E.R. Laws (ed.). 1990. Handbook of Pesticide
Toxicology, Classes of Pesticides, Vol. 3. Academic Press, Inc., NY
Occupational Health Services, Inc. 1993 (Nov. 17). MSDS for
Cypermethrin. 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 persistence
and
behavior in soil of four pyrethroid insecticides. Canadian Entomologist
113: 685-94.
Agnihotri, N.P. et al. 1986. Persistence of some synthetic
pyrethroid 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 to
honeybees of selected pyrethroid formulations applied to cotton in
Arizona. J. of Economic Entomology 81 (4): 1022-6.
U.S. Environmental Protection Agency. Jan. 3, 1989. Pesticide Fact
Sheet 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 in
sediment and water. Environmental Toxicology and Chemistry 4: 51-61.
Bradbury, S.P. and J.R. Coats. 1989. Toxicokinetics and
toxicodynamics of pyrethroid insecticides in fish. Environmental
Toxicology and Chemistry 8: 373-380.
Belanger, A. et al. 1990. A field study of four insecticides used
in strawberry protection. J. of Environmental Science and health, Part B
25 (5): 615-25.
Westcott, N.D. and R.A. Reichle. 1987. Persistence of deltamethrin
and cypermethrin on wheat and sweet clover. J. of Environmental Science
and 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 in
sediment and water. Environmental Toxicology and Chemistry 4: 51-61.
Bradbury, S.P. and J.R. Coats. 1989. Toxicokinetics and
toxicodynamics of pyrethroid insecticides in fish. Environmental
Toxicology and Chemistry 8: 373-380.
Haya, K. 1989. Toxicity of pyrethroid insecticides to fish.
Environmental Toxicology and Chemistry 8: 381-391.
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criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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