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
TRADE OR OTHER NAMES
Cyfluthrin is the active ingredient in many insecticide products
including Baythroid, Baythroid H, Attatox, Contur, Laser, Responsar, Solfac,
Tempo and Tempo H. Combination products include Baythroid TM (+
methamidophos) and Aztec (+ tebupirimphos) (1).
First registered by EPA in 1987, cyfluthrin is found in both restricted
use (RUP) and general use insecticides (2). Cyfluthrin containing products
may be classified by EPA as acute Toxicity Category II (bearing the signal
word "Warning") or Toxicity Category I (bearing the signal word "Danger")
based on its potential to cause eye damage (1). Currently, there are
tolerances for residues of cyfluthrin in or on raw agricultural products
ranging from 0.05 (hog meat) to 4.0 ppm (hops) (3). Note: These are subject
to change. Check with specific state regulations for local restrictions which
Cyfluthrin is a synthetic pyrethroid insecticide that has both contact
and stomach poison action. It is a non-systemic chemical used to control
cutworms, ants, silverfish, cockroaches, termites, grain beetles, weevils,
mosquitoes, fleas, flies, corn earworms, tobacco budworm, codling moth,
European corn borer, cabbageworm, loopers, armyworms, boll weevil, alfalfa
weevil, Colorado potato beetle, and many others. Its primary agricultural
uses have been for control of chewing and sucking insects on crops such as
cotton, turf, ornamentals, hops, cereal, corn, deciduous fruit, peanuts,
potatoes, and other vegetables. Cyfluthrin is also used in public health
situations and for structural pest control (4).
Cyfluthrin based insecticide formulations are available in the form of
emulsifiable concentrates, wettable powder, aerosol, granules, liquid, oil-in-
water emulsion and ULV oilspray (1). Typical application rates for
agricultural use range from 0.0125 - 0.05 pounds/acre, substantially lower
than many other commonly used insecticides. Pyrethrin and pyrethroid
formulations typically contain piperonyl butoxide which acts as a chemical
synergist. Typical carriers include organic solvents and water. It is
incompatible with azocyclotin.
Cyfluthrin is considered moderately toxic to mammals. The oral dose of
cyfluthrin that resulted in mortality to half of the test animals (LD50)
ranged from 869 - 1271 mg/kg in rats, 291 - 609 mg/kg in mice, >1000 mg/kg in
sheep, > 100 mg/kg in dogs and > 1000 mg/kg in rabbits (6). In inhalation
toxicity tests with rats, the concentration of cyfluthrin in air that resulted
in mortality to half of the test animals (LC50) was >1,089 ug/l in 1 hour
tests, and ranged from 469 - 592 ug/l in 4 hour tests (6). Although cyfluthrin
is an irritant to human skin, especially facial skin, it is not considered to
have high dermal toxicity. The dermal LD50 in tests with rats was > 5,000
mg/kg, and was not found to be a skin irritant or sensitizer in guinea pigs
and rabbits (5, 6).
Signs and Symptoms of Acute Poisoning
Although cyfluthrin is a skin and eye irritant in humans, pyrethroid
poisonings are rare. The main reason for their low toxicity in humans, is
that they are rapidly broken down in the human body by liver proteins, and
eliminated fairly quickly (see fate in humans and animals section). Also,
pyrethroids are not well absorbed into the bloodstream, contributing to their
moderate acute toxicity in mammals.
In laboratory tests where animals have been exposed to very large doses
of pyrethroids orally or by injection, there have been effects on the nervous
system. Symptoms of acute poisoning include irritability, excessive
salivation, uncoordinated gait, tremors, convulsions, and death. Cyfluthrin
may cause itching, burning, or stinging if it comes in contact with human
skin.These sensations can progress to a numbing effect that may last up to 24
hours. Usually, there is a 1-2 hour delay of skin irritation following
exposure, but it may occur immediately. Dermal irritation may be worsened by
sweating, exposure to sun or heat and application of water (7).
Long-term feeding studies have been conducted with mice, rats and dogs.
Invest-igations of blood chemistry, and necropsies of vital organs did not
indicate any organ specific toxicity. The only long-term effects of exposure
to cyfluthrin were the retardation of weight gain, and changes in some organ
weights associated with body weight effects in the high dose groups (6). In a
two-year feeding study with rats fed up to 450 ppm Baythroid, decreased body
weights were observed in males, and some inflamation of the kidney was
observed in females (8).
A three generation reproductive study in rats produced a systemic No
Observable Effect Level (NOEL) of 50 ppm (2 mg/kg/day), and a Low Observable
Effect Level (LOEL) of 150 ppm (7.5 mg/kg/day) based on decreased body weights
in pups. It was also determined that the NOEL and LOEL for viability of
offspring were 50 ppm and 150 ppm, respectively (8).
A developmental toxicity study in rats given doses of up to 30 mg/kg
cyfluthrin over days 6-15 of gestation resulted in a maternal NOEL of 3
mg/kg/day based on behavioral changes in gait and coordination, and a
teratogenic NOEL of 30 mg/kg/day (highest dose tested). Another study in
rabbits resulted in a maternal NOEL of 15 mg/kg/day based on fetal abortion
and resorption. No developmental abnormalities were observed at the highest
dose tested of 45 mg/kg/day (8).
There was no evidence of carcinogenicity in rats or mice.
Cyfluthrin was negative for mutagenicity.
Short and long term studies of the effects of cyfluthrin on mammalian
systems have resulted in pockets of inflamation in the kidneys of females, and
reversible damage to the sciatic nerve (this nerve controls sensation in the
Fate in Humans and Animals
Cyfluthrin metabolism in mammals occurs in two phases (biphasic), an
initial fast phase, and a slower second phase. Laboratory tests show that
about 60% of an intravenous dose of cyfluthrin is eliminated in the urine in
the first 24 hours, with only an additional 6% eliminated in the next 24
hours. Similarly, 20% of the administered dose was eliminated in the feces in
the first day, followed by 3-4% the next day. Another test with a single oral
dose of cyfluthrin showed that 98% of the material was eliminated by 48 hours
Effects on Birds
Cyfluthrin is of low toxicity to upland game birds and waterfowl. LD50
values range from >2,000 mg/kg in acute oral tests with bobwhite quail, to
>5,000 mg/kg in subacute tests with both mallard ducks and bobwhite quail (2).
Other tests with chicken hens have resulted in LD50 values of 4,500 - >5,000
mg/kg depending on the vehicle of administration (6). Little information was
found concerning the toxicity of cyfluthrin to songbirds. LD50 values for
canaries range from 250-1000 mg/kg (5).
Effects on Aquatic Organisms
Cyfluthrin is highly toxic to marine and freshwater organisms. The
concentration of cyfluthrin in water that resulted in the mortality of half of
the test organisms (LC50) was 0.00068 mg/l in rainbow trout, 0.0015 mg/l in
bluegill, 0.022 mg/l in carp, and 0.0032 mg/l in golden orfe (2, 5).
Cyfluthrin is exceptionally toxic to the freshwater invertebrate Daphnia
magna, (LC50 = 0.14 ng/l or .00000014 mg/l). Marine and estuarine
invertebrates are also extremely sensitive to cyfluthrin. The LC50 for mysid
shrimp was 2.42 ng/l and the EC50 for the eastern oyster was 3.2 ng/l. The
LC50 for the sheepshead minnow was 0.004 mg/l (2).
Effects on Other Animals (Nontaret species)
Cyfluthrin is highly toxic to bees with an LD50 of 0.037 mg/bee (2).
Pyrethroids are known to be highly toxic to other beneficial insects.
Breakdown of Chemical in Soil and Groundwater
Cyfluthrin is sensitive to breakdown by sunlight. On the surface of
soils, its half-life is 48-72 hours. It has a half-life of 56-63 days in
German loam and sandy loam soils, respectively, and has similar persistence in
soils under conditions of low oxygen (anaerobic). Cyfluthrin is very immobile
in soils, and is not considered a threat to contaminate groundwater (9). The
primary breakdown products of cyfluthrin are carbon dioxide and 4-fluoro-3-
phenyl-benzaldehyde (a compound of considerably lower toxicity than the parent
Breakdown of Chemical in Surface Water
Cyfluthrin is broken down quickly in surface water. Beacuse it is
realtively non-soluble, and less dense than water, it will float on the
surface film of natural waters. At the surface, it is subject to breakdown by
exposure to sunlight (1 day). It is stable to breakdown by water at acidic
pH, and quickly hydrolyzed in water under basic conditions (9).
Breakdown of Chemical in Vegetation
There is little information available about the breakdown of cyfluthrin
in vegetation. One study determined that very small amounts of cyfluthrin
residues remained on strawberries 7 days after the last of 3 weekly
applications (10). Another researcher identified a protein in tomatoes that
is capable of breaking down cyfluthrin (11). Researchers in Australia
demonstrated that cyfluthrin is stable and resistant to breakdown when used on
wheat in storage for up to 52 weeks (12).
PHYSICAL PROPERTIES AND GUIDELINES
|NOEL: ||50 ppm (2.5 mg/kg/day)
|LOEL: ||150 ppm (7.5 mg/kg/day)
|RfD: ||0.025 mg/kg/day
|CAS #: ||68359-37-5
|Form: ||pasty yellow mass
|Melting Point: ||60 degrees C
|Vapor Pressure: ||1.62 x 10 to the minus 8 mmHg
|Density: ||0.830 g/ml
|Solubility in Water: ||0.002 mg/ml @ 20 degrees C.
|Solubility in Other Solvents: ||> 200 g/l in dichloromethane and toluene, 10-20 g/l hexane, 20-50 g/l propan-2-ol
|Log Kow: ||5.62
|Chemical Name: ||Cyano(4-fluoro-3-phenoxy-phenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate.
|Molecular Formula: ||C22H18Cl2FNO3
Bayer Agricultural Products
PO Box 4913
Kansas City, MO 64120
Review by Basic Manufacturer:
Comments solicited: May and October, 1995
Comments received: not received
Meister, R.T. 1995. Farm Chemicals Handbook '95. Meister Publishing
Company. Willoughby, OH.
U.S. Environmental Protection Agency. 1987. Pesticide Fact Sheet
Number 164: Cyfluthrin. U.S. EPA, Office of Pesticide Programs. Washington,
U.S. Environmental Protection Agency. 1993. Complete Tolerance
Listing. Office of Pesticide Programs. U.S. EPA. Washington, DC.
Thomson, W.T. 1992. Agricultural Chemicals Handbook, Book 1. Thomson
Publications. Fresno, CA.
Worthing, C.E. (ed.). 1991. The Pesticide Manual: A World Compendium.
Ninth edition. Published by The British Crop Protection Council.
Pesticide Residues in Food-1987. Evaluations Part II Toxicology.
Cyfluthrin. pp. 53-78. JMPR.
Moran, D.P. 1989. Recognition and Management of Pesticide Poisonings.
Fourth edition. Health Effects Division, Office of Pesticide Programs, U.S.
EPA. Washington, DC.
IRIS Accession number 132. October 1993. Baythroid.
U.S. Environmental Protection Agency. 1992. Pesticide Environmental
Fate One Line Summary: Cyfluthrin. U.S. EPA, Environmental Fate and Effects
Division. Washington, DC.
McEwen, F.L., H.E. Braun, G.M. Richey, and R. Frank. 1986. Residues of
Synthetic Pyrethroid Insecticides on Horticultural Crops. Pestic. Sci.
Preiss, U., P.R. Wallnofer and G. Engelhardt. 1988. Partial
Purification and Properties of an Esterase From Tomato Cell Suspension
Cultures Hydrolyzing the Pyrethroid Insecticide Cyfluthrin. Pestic. Sci.
Noble, R.M. and D.J. Hamilton. 1985. Stability of Cypermethrin and
Cyfluthrin on Wheat in Storage. Pestic. Sci. 16:179-185.
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