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A Pesticide Information Project of Cooperative Extension Offices of
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Pesticide
Information
Profile
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Lambda cyhalothrin
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TRADE OR OTHER NAMES
Trade names for products containing lambda cyhalothrin include Charge,
Excaliber, Grenade, Hallmark, Icon, Karate, Matador, OMS 0321, PP321, Saber,
Samurai and Sentinel (1, 2).
REGULATORY STATUS
Lambda cyhalothrin is a Restricted Use Pesticide and so may be purchased
and used only by certified applicators (1, 2). It is in EPA Toxicity Class
II, and products containing it must bear the signal word WARNING (3).
INTRODUCTION
Lambda cyhalothrin is a synthetic pyrethroid insecticide and acaricide
used to control a wide range of pests in a variety of applications. Pests
controlled include aphids, Colorado beetles and butterfly larvae (2). Crops
on which it may be applied include cotton, cereals, hops, ornamentals,
potatoes, vegetables or others (2). It may also be used for structural pest
management or in public health applications to control insects such as
cockroaches, mosquitoes, ticks and flies which may act as disease vectors (2).
Lambda cyhalothrin is available as an emulsifiable concentrate, wettable
powder or ULV liquid (1, 2), and is commonly mixed with buprofezin,
pirimicarb, dimethoate or tetramethrin (2). It is compatible with most other
insecticides and fungicides (2).
Unless otherwise stated, data presented herein refer to the technical
product.
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Lambda cyhalothrin is moderately toxic in the technical form, but may be
highly toxic via some routes in formulation (e.g., as Karate). Available data
indicate that lambda cyhalothrin is moderately toxic via the oral route in
test animals. Reported oral LD50 values are 79 mg/kg and 56 mg/kg for male
and female rats, respectively (2, 4). The vehicle used was corn oil. The rat
oral LD50 has also been reported as 144 mg/kg (5). The reported rat LD50 for
the technical product is similar, 64 mg/kg (4). These indicate moderate acute
toxicity via the oral route of exposure.
No data were available regarding the acute toxicity of the technical
compound via the inhalation route, but for Karate the reported 4-hour
inhalation LC50s were 0.175 mg/L and 0.315 mg/L for female and male rats,
respectively (4). These data indicate a moderate to high toxicity via the
inhalation route for the formulated product Karate.
The technical product has reported dermal LD50s of 632 mg/kg and 696
mg/kg for male and female rats (vehicle used was propane-1,2-diol) (2, 4). It
has also been found to be non-irritating to the skin of rabbits (2, 4) and
non-sensitizing to the skin of guinea pigs (4) but may cause mild eye
irritation in rabbits (2).
The formulated product, Karate, however, causes severe primary skin
irritation in rabbits and mild skin sensitization in guinea pigs (4). Primary
eye irritation also was observed with the technical product (4).
In addition to the corrosive effects to skin and eyes, other acute
effects due to exposure to lambda cyhalothrin, like those of other
pyrethroids, will be mainly neuropathy (effects on the nervous system) (4, 5).
Cyhalothrin may act on ion channels within the nerve cells (neurons) to
disrupt proper function of the cells of both the peripheral and central
nervous systems (5). At lower doses, this may take the form of stable,
repetitive firing of the neuron, but high doses may result in depolarization
of the nerve cell and blockage of conduction (5).
These effects may result in observable effects such as: tingling, burning
or numbness sensations (particularly at the point of skin contact); tremors,
incoordination of movement , paralysis or other disrupted motor function; and
confusion or loss of consciousness (5). Since most pyrethroids are generally
absorbed only poorly through the skin (5, 6), the latter two systemic effects
are unlikely unless the compound has been ingested. Effects are generally
reversible due to rapid breakdown of the compound in the body (5, 6).
Like many compounds of the pyrethroid family, the observed toxicity of
lambda cyhalothrin may vary according to not only the concentration of the
active ingredient, but also according to the solvent vehicle (1).
CHRONIC TOXICITY
The principal toxic effects noted in chronic studies were decreased body
weight gain and decreased food consumption. These effects occurred in rats at
oral doses of 1.5 mg/kg/day (the highest dose tested) in a three-generational
study conducted in 1984 (4, 7). In a two-year study in rats, no effects were
observed at oral doses of 2.5 mg/kg/day and doses of up to 8.5 mg/kg/day
produced no observable changes in the function or structure of the liver or
nervous system (4, 7). In this study, decreased body weight gain and
decreased food consumption occurred at doses of 12.5 mg/kg/day as did
elevation of plasma triglycerides (4, 7).
In a 26 week feeding study on dogs, doses of 2.5 mg/kg/day disrupted
water absorption from the small intestine resulting in liquid feces (4, 7),
and at doses of 3.5 mg/kg/day and higher, neurological effects were noted (6).
In two teratology studies, no maternal toxicity was observed at doses of 10
mg/kg/day in both rats and rabbits (4, 7). It is unlikely that lambda
cyhalothrin would cause chronic effects in humans under normal conditions.
Reproductive Effects
In two studies, lambda cyhalothrin caused reduced body weight gain at
doses of 15 mg/kg/day in pregnant rats (highest dose tested) and at doses of
30 mg/kg/day in pregnant rabbits (also the highest dose tested) (4, 7), but
these doses produced no observable reproductive effects. There were reduced
numbers of viable offspring at doses of 50 mg/kg/day in the second and third
generations in the three-generational rat study noted above (4, 7). It is
unlikely that lambda cyhalothrin would cause reproductive effects in humans
under normal conditions.
Teratogenic Effects
No teratogenic or fetotoxic effects were observed in teratology studies
of lambda cyhalothrin in rats and rabbits at the highest doses tested in both
species (15 mg/kg/day and 30 mg/kg/day, respectively; 4, 7). Based on these
data, it is unlikely that lambda cyhalothrin causes teratogenic effects.
Mutagenic Effects
Lambda cyhalothrin produced negative results in all Ames mutagenicity
assays using five different test strains, both with and without metabolic
activation (2, 6). Results of other in-vitro cytogenetic assays and
chromosomal structural aberration tests indicated no mutagenic or genotoxic
effects were caused by lambda cyhalothrin (4, 6). The available evidence
suggests that lambda cyhalothrin is non-mutagenic and non-genotoxic.
Carcinogenic Effects
No carcinogenic effects have been noted in studies of lambda cyhalothrin
on various test animals (rats, rabbits, dogs) (4). The evidence regarding the
carcinogenicity of lambda cyhalothrin is inconclusive, but suggests that it is
probably not carcinogenic.
Organ Toxicity
No specific target organs or organ systems have been identified in the
available studies of chronic toxicity. The nervous system may be affected
after acute exposure.
Fate in Humans & Animals
In rat studies, lambda cyhalothrin is rapidly metabolized and excreted
via the urine and feces (2). Hydrolytic cleavage of the ester bond occurs,
forming more polar, water-soluble compounds which are less toxic and more
easily eliminated (2, 7).
ECOLOGICAL EFFECTS
Effects on Birds
Lambda cyhalothrin's toxicity to birds ranges from slightly toxic to
practically non-toxic. In the mallard duck, the reported oral LD50 is greater
than 3,950 mg/kg (2, 4), and the reported dietary LC50 is 3,948 ppm (4). In
bobwhite quail the reported dietary LC50 is greater than 500 ppm (2, 4).
There is evidence that it does not accumulate in the eggs or tissues of birds
(2).
Effects on Aquatic Organisms
Lambda cyhalothrin is very highly toxic to many fish and aquatic
invertebrate species. Reported LC50s in these species are as follows:
bluegill sunfish, 0.21 ug/L (2, 4); rainbow trout, 0.24 ug/L (2, 4); Daphnia
magna, 0.36 ug/L (4); mysid shrimp, 4.9 ng/L (4); sheepshead minnow, 0.807
ng/L (4). A median effect concentration, EC50 (i.e. the concentration at
which the effect occurs in 50% of the test population), for the eastern oyster
of 0.59 ng/L has been reported (4).
Bioconcentration is possible in aquatic species, but bioaccumulation is
not likely. Bioconcentration in channel catfish has been reported as minimal,
with rapid depuration (elimination) (8). A bioconcentration factor of 858 has
been reported in fish (4, species unspecified), but concentration was confined
to non-edible tissues and rapid depuration was observed (4).
Effects on Other Animals (Nontarget species)
Lambda cyhalothrin is highly toxic to bees, with a reported oral LD50 of
38 ng/bee and reported contact LD50 of 909 ng/bee (0.9 ug/bee) (4).
Environmental Fate
Breakdown of Chemical in Soil and Groundwater
Lambda cyhalothrin is moderately persistent in the soil environment.
Reported field half-lives range from four to 12 weeks (4, 8, 9). Its field
half-life is probably close to 30 days in most soils (9). It shows a high
affinity for soil; the reported Koc is 180,000 (9). Lambda cyhalothrin is not
expected to be appreciably mobile in most soils. There is little potential for
groundwater contamination. Soils with high sand content or with very low
organic matter content may tend to retain the compound to a lesser degree. In
field studies of Karate, leaching of lambda cyhalothrin and its degradates
from the soil were minimal (2, 4).
Breakdown products formed in the soil environment are similar to those
formed in mammalian systems, via the hydrolysis of the central ester bond and
oxidation (2). Breakdown rates of both the technical product and Karate were
similar under aerobic and anaerobic conditions (4, 8).
Breakdown of Chemical in Surface Water
Lambda cyhalothrin has extremely low water solubility and is tightly
bound to soil, it is therefore not expected to be prevalent in surface waters.
One possible source of infiltration into surface waters would be surface
runoff. In this event, the compound would most probably remain bound to the
solid particle and settle to the bottom.
Breakdown of Chemical in Vegetation
No data were available regarding the breakdown of lambda cyhalothrin in
vegetation.
PHYSICAL PROPERTIES AND GUIDELINES
Lambda cyhalothrin is a colorless solid at room temperature, but may
appear yellowish in solution.
Exposure Guidelines:
| ADI: | Not Available |
| HA: | Not Available |
| RfD: | 0.005 mg/kg/day (3) |
| PEL/TLV: | Not Available |
Physical Properties:
| Chemical Name: | (RS)-alpha-cyano-3-phenoxybenzyl 3-(2-chloro-3,3,3-trifluoropropenyl)-2,2,-dimethylcyclopropanecarboxylate (2) |
| CAS: | 91465-08-6 (2) |
| Molecular Weight: | 449.9 (2) |
| Water solubility: | 0.005 mg/L @ pH 6.5 and 20 degrees C (2) |
| Solubility in other solvents: | acetone v.s, methanol v.s., toluene v.s., hexane v.s. (2) |
| Melting Point: | 49.2 degrees C |
| Vapor Pressure: | negligible at 20 degrees C (2) |
| Partition Coefficient (octanol/water): | 10,000,000 (2) |
| Adsorption Coefficient: | 180,000 (9) |
BASIC MANUFACTURER
Zeneca Agricultural Products
1800 Concorde Pike
Wilmington, DE 19897
Telephone: 800-759-4500
Review by Basic Manufacturer:
Comments solicited: June, 1995
Comments received: Not received
REFERENCES
Meister, R. T. (ed.) 1992. Farm Chemicals Handbook '92, Meister
Publishing Co. Willoughby, OH.
Royal Society of Chemistry. 1991 (as updated). The Agrochemicals
Handbook, Royal Society of Chemistry Information Services. Cambridge, UK.
US Archives and Records Administration. 1994. 40 CFR 156.10, US
Government Printing Office. Washington, DC.
US Environmental Protection Agency. 1988. Fact Sheet Number 171:
Karate (PP321). Washington, DC.
Ray, D.E. 1991. Pesticides Derived from Plants and Other Organisms In
Hayes Jr., Wayland, and Edward R. Laws, Jr. (eds.) Handbook of Pesticide
Toxicology. Academic Press, Inc. New York, NY.
US Environmental Protection Agency. 1995. File: Cyhalothrin,
Hazardous Substances Data Bank (HSDB). National Library of Medicine "Toxnet"
Database, 4/95.
US Environmental Protection Agency. 1995. File: Cyhalothrin,
Integrated Risk Information System (IRIS). National Library of Medicine
"Toxnet" Database, 4/95.
US Environmental Protection Agency. 1992. Environmental Fate and
Effects Division. Pesticide Environmental Fate One Line Summary:
Lambdacyhalothrin. Washington, DC.
Wauchope, R.D., Buttler, T.M., Hornsby A.G., Augustijn-Beckers, P.W.M.
and Burt, J.P. 1992. SCS/ARS/CES Pesticide Properties Database for
Environmental Decisionmaking. Reviews of Environmental Contamination and
Toxicology, Vol. 123.
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site is not a substitute for a pesticide label. Trade names used herein
are for convenience only; no endorsement of products is intended, nor is
criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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