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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.


Publication Date: 9/93


Some trade names include AC 222705, Cybolt and Pay-Off (discontinued).


Some applications of flucythrinate may be classified as Restricted Use Pesticides (RUP) by the EPA (1). Restricted Use Pesticides may be purchased and used only by certified applicators. Pesticides containing flucythrinate must bear the signal word "Danger" on the product label (1) because of this active ingredient's potential to cause eye irritation and because of its high oral toxicity (3).


Flucythrinate is a synthetic pyrethroid used to control insect pests in apples, cabbage, field corn, head lettuce and pears, and to control Heliothis spp. in cotton (1). It is used primarily on cotton (3). It is available in emulsifiable concentrate and wettable powder formulations (1).



Flucythrinate is a highly toxic pesticide (1). Rats fed 15 mg/kg/day for 28 days showed severe motor symptoms (involuntary muscular movement), and rats fed 7.5 mg/kg/day showed moderate motor symptoms. In both cases, symptoms disappeared within 48 hours after resumption of a normal diet (2). Symptoms exhibited by animals in short-term feeding studies include vomiting, diarrhea, incoordination, excessive salivation and urination, and hypersensitivity (12).

Flucythrinate can cause extreme eye irritation (3) and mild to severe skin irritation (12). It failed to produce allergic reactions in guinea pigs (3, 12). When 130 ug/cm2 was applied to the ear lobes of human volunteers, flucythrinate caused severe paresthesia (i.e. abnormal sensations such as burning or tingling) which began 30 minutes after the application and continued for 24 hours. Of four pyrethroids tested in this way, flucythrinate produced the most severe paresthesia (2). Skin on the forearm proved to be less sensitive than the earlobes. When 13.8 mg/cm2 was applied to the forearms of volunteers, paresthesia appeared 4 to 5 hours later and lasted for 3 days (2).

In a 21-day delayed neurotoxicity study with hens, the NOEL was 5,000 mg/kg, the highest dose tested (5).

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 technical flucythrinate in male rats is 81 mg/kg (5), 67 mg/kg in female rats (1, 2), and 76 mg/kg in mice (2). The dermal LD50 in rabbits is >1,000 mg/kg (1), and on guinea pigs is >2,000 mg/kg (3). The 4-hour inhalation LC50 for technical flucythrinate in rats is 0.064 mg/l (12).


No adverse effects were observed when rats and dogs were fed flucythrinate for 90 days at doses of up to 3 mg/kg for rats and 3.75 mg/kg for dogs (5). Dogs fed 7.5 mg/kg/day for 2 years exhibited vomiting and decreased body weight gain. The NOEL for this study was 0.75 mg/kg/day (12). Rats fed 6 mg/kg/day for 2 years also exhibited decreased body weight gain. The systemic NOEL for this study was 3 mg/kg/day (12).

Reproductive Effects

In a 3-generation reproductive study, rats given 1.5, 3 or 6 mg/kg doses showed reduced parental and pup weights, and decreased pup survival. Reduced litter size occurred at 3 and 6 mg/kg. The NOEL was 1.5 mg/kg (5, 12).

Teratogenic Effects

Flucythrinate does not cause birth defects (2). No teratological effects were observed in studies with rats or rabbits. The highest dose tested was 8.0 mg/kg/day for rats and 60 mg/kg/day for rabbits (5).

Mutagenic Effects

Flucythrinate is not mutagenic (2). An Ames test using several strains of bacteria exposed to concentrations as high as 1,000 micrograms (ug)/plate and a rat dominant-lethal test at up to 10.0 mg/kg both showed no evidence that flucythrinate causes mutations (5, 12).

Carcinogenic Effects

No tumor formation was observed in mice or rats fed doses of up to 6 mg/kg for 24 months (5, 12).

Organ Toxicity

Pyrethroids may cause adverse effects on the central nervous system. Long-term feeding studies have shown increased liver and kidney weights and adverse changes in liver tissues in test animals (9).

Fate in Humans and Animals

Flucythrinate is rapidly metabolized by ester cleavage and oxidation (2). When radio-labeled flucythrinate was administered orally to rats, 15 to 24% was eliminated in the urine and 37 to 65.6% was eliminated in the feces during the first 24 hours. Within 8 days, 95.8 to 100% of the dose was eliminated in either urine or feces. A large amount of the chemical recovered in the feces was unaltered flucythrinate, suggesting that this portion passed through the gut without being absorbed into the bloodstream (3). Metabolites of flucythrinate are considered to be of no toxicological significance (12).


Effects on Birds

Pyrethroids are practically non-toxic to bird species.

Effects on Aquatic 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 (9).

Flucythrinate accumulated in the edible tissues of bluegill sunfish to 487 times the concentration in surrounding waters (11).

Generally, the lethality of pyrethroids to fish increases with increasing octanol/water partition coefficients (10).

Effects on Other Animals (Nontarget species)

No information was found.


Breakdown of Chemical in Soil and Groundwater

Flucythrinate is nearly insoluble in water and it has a strong tendency to bind to soil particles. It is therefore unlikely to contaminate groundwater (6). A soil half-life of 21 days has been reported (6).

When applied to a sandy loam soil, 80% of the parent compound was recovered after 2 months, indicating that flucythrinate decomposes slowly in soil. The only degradate found at the end of 2 months was m-phenoxy benzoic acid (11). In field soils, dissipation occurred within 2.2 months, with most residues found within the top 3 inches of soil (11).

Following multiple applications to sand, clay and loam soils, there was no accumulation of flucythrinate in the upper 6 inches of soil. Residues were found in the upper 3 inches of soil from 47 to 50 days following application (11).

Barley, snapbeans and beets grown in the greenhouse contained residues of less than 0.01 ppm after application of 0.05 pounds of flucythrinate per acre. No residues were found in treated crops grown in the field (11).

Breakdown of Chemical in Surface Water

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 (8).

Breakdown of Chemical in Vegetation

No information was found.


Flucythrinate is a dark amber, viscous liquid. It is stable in neutral and acidic conditions (1, 3) and it is stable in light (2).

Because this compound is an eye irritant, workers handling flucythrinate should wear goggles or a face shield (1).

Exposure Guidelines:

No occupational exposure limits have been established for flucythrinate by OSHA, NIOSH or ACGIH (7).

ADI: 0.025 mg/kg/day, based on a NOEL of 2.5 mg/kg in a 2-year rat feeding study and a safety factor of 100 (4).

Physical Properties:

CAS #: 70124-77-5
Chemical Name: alpha-Cyano-3-phenoxybenzyl-(S)-2-[4-(di-fluoromethoxy)phenyl]-3-methylbutyrate (2)
Chemical Class/Use: Synthetic pyrethroid insecticide
Density: 1.19 gm/ml at 22 degrees C (2)
H20 solubility: 0.5 ppm at 21 degrees C; 0.48 ppm at 25 degrees C (1, 3)
Solubility in other solvents: soluble in most organic solvents (1); soluble in acetone, xylene and isopropanol (3).
Boiling point: 108 degrees C at 0.35 mm Hg (3)
Vapor pressure: 8.7 x 10-9 mm Hg at 25 degrees C (2, 6); 2.4 x 10-7 mm Hg at 45 degrees C (3)
Koc: 100,000 gm/ml (6)


DuPont Agricultural Products
Walker's Mill
Barley Mill Plaza
P.O. Box 80038
Wilmington, DE 19880-0038

Review by Basic Manufacturer:

Comments solicited: June, 1993
Comments received:


  1. Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister Publishing Company, Willoughby, OH.
  2. Hayes, W.J. and E.R. Laws (eds.). 1990. Handbook of Pesticide Toxicology, Classes of Pesticides, Vol. 2. Academic Press, Inc., NY.
  3. Mehler, L.N. 1989 (March 17). Assessment of Human Exposure to Flucythrinate, HS-1510. California Department of Food and Agriculture, Sacramento, CA.
  4. U.S. Environmental Protection Agency. Jan. 25, 1988. Pesticide tolerances for cyano(4-fluoro-3-phenoxyphenyl)methyl 3-(2,2- dichloroethenyl)-2,2-dimethyl-cyclopropanecarboxylate). Federal Register, 53 (15): 1916-7.
  5. _____. May 22, 1985. Pesticide tolerance on an agricultural commodity; flucythrinate. Federal Register, 50 (99): 21050-1.
  6. 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.
  7. Occupational Health Services, Inc. 1993 (Nov. 17). MSDS for Resmethrin. OHS Inc., Secaucus, NJ.
  8. 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.
  9. Bradbury, S.P. and J.R. Coats. 1989. Toxicokinetics and toxicodynamics of pyrethroid insecticides in fish. Environmental Toxicology and Chemistry 8: 373-380.
  10. Haya, K. 1989. Toxicity of pyrethroid insecticides to fish. Environmental Toxicology and Chemistry 8: 381-391.
  11. US Environmental Protection Agency. Sept. 27, 1989. Pesticide Environmental Fate One Line Summary. Environmental Fate and Effects Division, US EPA, Washington, DC.
  12. US Environmental Protection Agency. Nov. 15, 1989. Tox Oneliners: Pay-off. Office of Pesticides/HED/SACB, US EPA, Washington, DC.