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
Publication Date: 9/93
TRADE OR OTHER NAMES
Some trade names include Chrysron, Crossfire, Pynosect, Raid Flying
Insect Killer, Scourge, Sun-Bugger #4, SPB-1382, Synthrin, Syntox, Vectrin and
Pesticides containing resmethrin must bear the signal word "Caution"
on the product label (1). All products containing resmethrin for mosquito or
other pest control at aquatic sites are classified as Restricted Use
Pesticides (RUP) by the EPA because resmethrin is toxic to fish (11).
Restricted Use Pesticides may be purchased and used only by certified
Resmethrin is a synthetic pyrethroid used for control of flying and
crawling insects in homes, greenhouses, indoor landscapes, mushroom houses,
industrial sites, stored product insects and for mosquito control (1). It is
also used for fabric protection, pet sprays and shampoos, and it is applied to
horses or in horse stables (11).
Resmethrin is moderately toxic by ingestion and slightly toxic through
the skin (2). Dermal exposure may lead to numbness, itching, burning,
tingling sensations. Symptoms of exposure by any route may include
incoordination, twitching, loss of bladder control, and seizures (2).
Resmethrin may cause eye irritation (2). It failed to cause allergic skin
reactions in guinea pigs (1), but may cause skin irritation (11).
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 resmethrin in rats is > 2,500 mg/kg (1) or
1,244 mg/kg (2). Its oral LD50 in mice is 300 mg/kg (2). The dermal LD50
for technical resmethrin on rats is > 3,000 mg/kg (1), on rabbits is > 2,500
mg/kg, and on mice is > 5,000 mg/kg (2).
The lethal concentration fifty, or LC50, is that concentration of a
chemical in air or water that kills half of the experimental animals exposed
to it for a set time period. The 4-hour inhalation LC50 for resmethrin is >
9.49 mg/l (11).
In a chronic feeding study with rats, the lowest dose tested (500 ppm
or 25 mg/kg/day) caused liver enlargement. At 2,500 ppm (125 mg/kg/day),
there were pathological liver changes in addition to increased liver weights.
Doses of 5,000 ppm (250 mg/kg/day) caused increased thyroid weight and thyroid
The NOEL in a chronic feeding study with dogs was 10 mg/kg/day (11).
In a 90-day inhalation study with rats, 0.1 mg/l, the lowest dose
tested, produced behavioral changes, decreased blood glucose levels in males,
and decreased boy weights and increased serum urea levels in females (11).
A 3-generation study with rats showed a slight increase in premature
stillbirths and a decrease in pup weight at 25 mg/kg, the lowest dose tested
No birth defects were observed in the offspring of rabbits given doses
as high as 100 mg/kg (5). Skeletal aberrations were seen in the offspring of
rats given doses higher than 40 mg/kg/day (11).
Resmethrin was not mutagenic in a test performed with the bacterium,
Salmonella typhimurium (8).
No evidence of tumor formation was observed in a 2-year rat feeding
study with doses as high as 250 mg/kg/day, nor in an 85-week study with mice
given doses as high as 50 mg/kg/day (5, 11).
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 (2). However, EPA reports
that resmethrin was not neurotoxic to rats at doses of 62.5 mg/kg for 32
weeks, 250 mg/kg for 30 days, or 632 mg/kg for 7 days (5). In a 2-year
feeding study with rats fed up to 250 mg/kg of resmethrin, increases in
liver weight and liver lesions occurred at 125 mg/kg (5). Increased liver
weights occurred in dogs fed 30 mg/kg/day for 180 days. The NOEL in this
study was 10 mg/kg/day (5).
Fate in Humans and Animals
When oral doses of 10 mg/kg radio-labeled resmethrin were given to
laying hens, 90% of the dose was eliminated in urine and feces within 24 hours
(7). In another study with hens given the same treatment, radioactive
residues were low in hens sacrificed 12 hours after the treatment, with the
highest levels found in the liver and kidneys. Low levels of radioactivity
were found in the hens' eggs, with levels peaking on 1 day after treatment in
the whites and 4 to 5 days after treatment in the yolks (10).
Effects on Birds
Resmethrin is slightly toxic to birds. Its LD50 in California quail
is > 2,000 mg/kg (11).
Effects on Aquatic Organisms
Resmethrin is highly toxic to fish. The LC50 for resmethrin in
mosquito fish is 0.007 ppm (6). The LC50 for resmethrin synergized with
piperonyl butoxide in red swamp crawfish, Procambarus clarkii, is 0.00082 ppm
(9). The LC50 in bluegill sunfish is 0.75 to 2.6 ug/l, and 0.28 to 2.4 ug/l
in rainbow trout (11).
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 (13).
Generally, the lethality of pyrethroids to fish increases with increasing
octanol/water partition coefficients (14).
Effects on Other Animals (Nontarget species)
Resmethrin is highly toxic to bees, with an LD50 of 0.063 ug/bee (11).
Resmethrin breaks down in the presence of light and humidity. Its
half-life in the environment is 15 minutes (3). Degradation end-products
reported for resmethrin are chrysanthemic acid, benzaldehyde, benzyl alcohol,
benzoic acid, phenylacetic acid, and various esters (4).
Breakdown of Chemical in Soil and Groundwater
No information was found.
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 (12).
Breakdown of Chemical in Vegetation
No information was found.
PHYSICAL PROPERTIES AND GUIDELINES
Resmethrin is a waxy, off-white to tan solid with an odor
characteristic of chrysanthemums (1). It is stable under normal
temperatures and pressures,
but decomposes in the presence of alkalis and light. It poses a fire and
explosion hazard in the presence of strong oxidizers and a slight fire hazard
if exposed to heat or flame. It may burn, but does not readily ignite.
Thermal decomposition may release toxic oxides of carbon (2). Resmethrin
dust-air mixtures may ignite or explode. Contact with strong oxidizers,
excessive heat, sparks and open flame should be avoided (2). Protect
formulations containing resmethrin from exposure to air or light. Containers
should be kept tightly closed (2).
Workers handling resmethrin should wear protective clothing to prevent
contact with the skin (1).
No occupational exposure limits have been established for resmethrin
by OSHA, NIOSH or ACGIH (2).
|ADI: ||0.1250 mg/kg/day based on chronic feeding and 3-generation reproduction studies with rats and a 200-fold safety factor (5).
|MPI: ||7.50 mg/day for a 60 kg person (5)
|CAS #: ||10453-86-8
|Chemical Name: ||([5-(phenylmethyl)-3-furanyl] methyl 2,2-dimethyl-3-(2-methyl-1-propenyl(cyclopropanecarboxylate) or 5-benzyl-3-furylmethyl (1RS)-cis,trans-chrysanthemate
|Chemical Class/Use: ||Synthetic pyrethroid insecticide
|Specific gravity: ||1.044 (technical) (4)
|Density: ||8.70 pounds/gal (11)
|H20 solubility: ||insoluble in water (1); < 1 ppm at 30 degrees C (2)
|Solubility in other solvents: ||10% in kerosene; soluble in hexane, xylene, methylene chloride, isopropyl alcohol and aromatic petroleum hydrocarbons; moderately soluble in methanol (1, 2).
|Melting point: ||109-118 degrees F (43-48 degrees C) (2)
|Boiling point: ||345 degrees F (174 degrees C) at 0.0008 mm Hg (2); 180 degrees C at 0.1 mm Hg (3, 4)
|Flashpoint: ||> 200 (technical) (4).
|Vapor pressure: ||negligible; 2.58 mm Hg at 200 degrees C (11)
Fairfield American Corp.
201 Route 17 N.
Rutherford, NJ 07070
Review by Basic Manufacturer:
Comments solicited: April, 1993
Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister
Publishing Company, Willoughby, OH.
Occupational Health Services, Inc. 1993 (Nov. 17). MSDS for
Resmethrin. OHS Inc., Secaucus, NJ.
National Coalition Against the Misuse of Pesticides. Resmethrin.
Pesticides and You, Dec. 1987: page 6. NCAMP, Washington, DC.
Penick Corp. 1976. Technical Information Sheet: SBP-1382*
(Resmethrin) Pesticide Technology Dept., Penick Corp., Orange, NJ.
U.S. Environmental Protection Agency. August 10, 1983. Tolerances
for pesticides in food administered by EPA; Resmethrin. Federal Register 48
Tietze N.S., et al. 1991. Acute toxicity of mosquitocidal compounds
to young mosquitofish, Gambusia affinis. J. of the American Mosquito
Control Assoc. 7 (2): 290-293.
Christopher, R.J., et al. 1989. Metabolism of cis- and trans-
resmethrin in laying hens. J. Agric. Food Chem. 37 (3): 800-808.
Herrera, A. and E. Laborda. 1988. Mutagenic activity in synthetic
pyrethroids in Salmonella typhimurium. Mutagenesis 3 (6): 509-514.
Holck, A.R. and C.L. Meek. 1987. Dose-mortality responses of
crawfish and mosquitoes to selected pesticides. J. of the American Mosquito
Control Assoc. 3 (3): 407-411.
Christopher, R.J., et al. 1985. Distribution and depletion of
carbon-14 resmethrin isomers administered orally to laying hens. Pesticide
Science 16 (4): 378-382.
U.S. Environmental Protection Agency. Dec. !988. Pesticide Fact
Sheet Number 193: Resmethrin. 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.
Haya, K. 1989. Toxicity of pyrethroid insecticides to fish.
Environmental Toxicology and Chemistry 8: 381-391.