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CYHALOTHRIN
CASRN: 68085-85-8
For other data, click on the Table of Contents
Human Health Effects:
Toxicity Summary:
Metabolic studies have been carried out on /various mammalian species/. In
rats and dogs, cyhalothrin has been shown to be well absorbed after oral administration,
extensively metabolized, and eliminated as polar conjugates in urine. ... Residues
in fats were eliminated with a half-life of 23 days. ... In all mammalian species
investigated, cyhalothrin has been found to be extensively metabolized as a
result of ester cleavage to the cyclopropanecarboxylic acid and 3-phenoxybenzoic
acid, and eliminated as conjugates. In fish, the main residue in tissues consists
of unchanged cyhalothrin, and there are lower levels of the ester cleavage products.
Under laboratory conditions of constant toxicant concentrations, cyhalothrin
and lambda-cyhalothrin are highly toxic to fish and to aquatic invertebrates.
... Accumulation studies conducted under laboratory conditions with constant
concentration show that rapid uptake takes place in fish ... Since the compound
is rapidly absorbed and degraded under natural conditions, there will not be
any practical problems concerning the accumulation of residues or the toxicity
of cyhalothrin or lambda-cyhalothrin in aquatic species. Cyhalothrin and lambda-cyhalothrin
are virtually non-toxic to birds ... Under laboratory conditions, cyhalothrin
and lambda-cyhalothrin are toxic to honey bees ... However, in the field the
hazard is lower ... Cyhalothrin and lambda-cyhalothrin are type II pyrethroids;
clinical signs /of toxicity/ include ataxia, unsteady gait, and hyperexcitability.
In the rabbit, cyhalothrin is a moderate eye irritant and lambda-cyhalothrin
is a mild eye irritant; both are mild skin irritants. /Cyhalothrin/ is a moderate
skin sensitizer in the guinea pig. Lambda-cyhalothrin is not a skin sensitizer.
... Cyhalothrin and lambda-cyhalothrin gave negative results in a range of in
vivo and in vitro assays designed to detect gene mutations, chromosomal damage,
and other genotoxic effects. When orally administered to the rat and rabbit
during the period of major organogenesis, cyhalothrin was neither embryotoxic
or teratogenic at dose levels that elicited maternal toxicity ... In manufacturing,
formulation, laboratory work and field usage, /human/ symptoms of subjective
facial sensation have been reported. ... Subjective facial skin sensations,
which may be experienced by people who handle cyhalothrin and lambda-cyhalothrin
are believed to be brought about by repetitive firing of sensory nerve terminals
in the skin. They may be considered as an early warning signal indicating that
overexposure of the skin has occurred. ... The exposure of the general population
to cyhalothrin and lambda-cyhalothrin is expected to be very low and is not
likely to present a hazard under recommended conditions of use. ... Cyhalothrin
and lambda-cyhalothrin are unlikely to present a hazard to those occupationally
exposed. ... Under laboratory conditions cyhalothrin and lambda-cyhalothrin
are highly toxic to fish, aquatic arthropods, and honey bees. However, under
field conditions, lasting adverse effects are not likely to occur under recommended
conditions of use.
Human Toxicity Excerpts:
Laboratory workers and manufacturing plant and field operators handling natural
and synthetic pyrethroids, including cyhalothrin and lambda-cyhalothrin, have
noticed a transient skin sensation in the periorbital area of the face and other
sites after direct skin exposure. It has been suggested that these sensations
are caused by spontaneous repetitive firing of sensory nerve fibres or nerve
endings, whose threshold has been transiently lowered by the compound, localized
around the sites of exposure. Symptoms from exposure to a synthetic pyrethroid
generally start 30 min to 1 hr after exposure and last for several hours, sometimes
up to 2 days. They almost always affect the facial area, producing a tingling,
burning, or numb sensation that has been variously described as paraesthesia,
dysaesthesia, or subjective facial sensation The latter term appears most appropriate
as no objective signs of abnormality of nerve function have been found in workers
suffering from these effects and the facial area is by far the most commonly
affected.
Cyhalothrin is known to produce an effect described as subjective facial sensation
in some people working with this compound. Subjective facial sensation is a
transient phenomenon; symptoms are not associated with objective physical signs
and recovery appears to be complete. It is likely that subjective facial sensation
arises from direct facial contact with the chemical particularly from touching
the face with contaminated gloves or hands. This would also help to explain
the effect of formulation or concentration as these could affect the rate of
dermal penetration and therefore access of the chemical to the nerve endings.
It appears unlikely that individual sensitivity is important in the development
of symptoms following exposure. It is more likely to be related to the amount
of the chemical that comes into contact with the facial skin.
In March 1990 a study was carried out in the village of Kicheba, United Republic
of Tanzania, in which the pyrethroid insecticide lambda-cyhalothrin was sprayed
on all the internal surfaces of houses and other shelters at a coverage of about
25 mg of active ingredient per sq m. Every day for 6 days, 12 spraymen and 3
squad leaders were interviewed about symptoms of overexposure to the insecticide.
Each sprayman used up to 62 g of lambda-cyhalothrin over 2.7-5.1 hr every day.
All the spraymen complained at least once of symptoms that were related to exposure
to lambda-cyhalothrin, the commonest being itching and burning of the face,
and nose or throat irritation frequently accompanied by sneezing or coughing.
Facial symptoms occurred on non-protected areas only. The symptoms were experienced
at various times after the beginning of exposure and disappeared before the
following morning. The number of subjects affected and the duration of their
facial symptoms were proportional to the amount of compound sprayed. A sample
of individuals was interviewed 1 day and 5-6 days after their houses had been
sprayed. One woman, who entered her house 30 min after the end of spraying,
complained of periorbicular itching, but this lasted only a few minutes. No
other significant, insecticide related adverse effect was reported by the inhabitants
of the sprayed houses.
Contact allergy from pyrethroids ... has not been observed. /Pyrethroids/
The allergenic properties of pyrethroids /with early pyrethrum preparations/
are marked in comparison with other pesticides. Many cases of contact dermatitis
and respiratory allergy have been reported. Persons sensitive to ragweed pollen
are particularly prone to such reactions. Preparations containing synthetic
pyrethroids are less likely to cause allergic reactions than are the preparations
made from pyrethrum powder. /Pyrethroids/
Some pyrethroid (eg, deltamethrin, fenvalerate, cyhalothrin, lambda-cyhalothrin,
flucythrinate, and cypermethrin) may cause a transient itching and/or burning
sensation in exposed human skin. /Synthetic pyrethroids/
Synthetic pyrethroids are neuropoisons acting on the axons in the peripheral
and central nervous systems by interacting with sodium channels in mammals and/or
insects. A single dose produces toxic signs in mammals, such as tremors, hyperexcitability,
salivation, choreoathetosis, and paralysis. ... At near-lethal dose levels,
synthetic pyrethroids cause transient changes in the nervous system, such as
axonal swelling and/or breaks and myelin degeneration in sciatic nerves. They
are not considered to cause delayed neurotoxicity of the kind induced by some
organophosphorus compounds. /Synthetic prethroids/
The clinical manifestations of inhalation exposure to pyrethrins can be local
or systemic. Localized reactors confined to the upper respiratory tract include
rhinitis, sneezing, scratchy throat, oral mucosal edema, and even laryngeal
mucosal edema. Localized reaction of the lower respiratory tract include cough,
shortness of breath, wheezing, and chest pain. An asthmalike reaction occurs
with acute exposures in sensitized patients. Hypersensitivity pneumonitis characterized
by chest pain, cough, dyspnea, & bronchospasm may occur in an individual
chronically exposed. /Pyrethrum and synthetic pyrethroids/
The low toxicity of pyrethroids in mammals is due largely to their rapid biotransformation
by ester hydrolysis and/or hydroxylation. /Pyrethroids/
Skin, Eye and Respiratory Irritations:
Immediately irritating to the eye. /Pyrethrins/
The chief effect from exposure ... is skin rash particularly on moist areas
of the skin. ... May irritate the eyes. /Pyrethroids/
Medical Surveillance:
Initial medical screening: Employees should be screened for history of certain
medical conditions ... which might place the employee at increased risk from
/pyrethroid/ exposure. Chronic respiratory disease: In persons with chronic
respiratory disease, especially asthma, the inhalation of /pyrethroids/ might
cause exacerbation of symptoms due to its sensitizing properities. Skin disease:
/Pyrethroids/ can cause dermatitis which may be allergic in nature. Persons
with pre-existing skin disorders may be more susceptible to the effects of this
agent. Any employee developing the above-listed conditions should be referred
for further medical examination. /Pyrethrum/
Populations at Special Risk:
Chronic respiratory disease: In persons with chronic respiratory disease,
especially asthma, the inhalation of /pyrethroids/ might cause exacerbation
of symptoms due to its sensitizing properities. Skin disease: /Pyrethroids/
can cause dermatitis which may be allergic in nature. Persons with pre-existing
skin disorders may be more susceptible to the effects of this agent. ... /Pyrethroids/
Probable Routes of Human Exposure:
Occupational exposure to cyhalothrin may occur through inhalation of dust
and dermal contact with this compound at workplaces where cyhalothrin is produced
or used. Monitoring data indicate that the general population may be exposed
to cyhalothrin via ingestion of food containing residues of this compound. (SRC)
Emergency Medical Treatment:
Emergency Medical Treatment:
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The following Overview, *** PYRETHRINS ***, is relevant for this HSDB record chemical. |
| Life Support: |
o This overview assumes that basic life support measures
have been instituted.
|
| Clinical Effects: |
SUMMARY OF EXPOSURE
0.2.1.1 ACUTE EXPOSURE
o The mammalian toxicity of natural pyrethrins is
generally low. Very young children are perhaps more
susceptible to poisoning because they may not hydrolyze
the pyrethrum esters efficiently. In humans, allergic
reactions are the main toxic manifestations of
pyrethrin exposure.
1. Pyrethrum and the pyrethrins produce typical type I
motor symptoms in mammals. Severe type I poisoning
may include the following signs in humans:
Severe fine tremor
Marked reflex hyperexcitability
Sympathetic activation
Paresthesia (dermal exposure)
o DERMAL - These compounds are not primary irritants.
The chief effect, however, from exposure is dermatitis.
The usual lesion is a mild erythematous dermatitis with
vesicles, papules in moist areas, and intense pruritus;
a bulbous dermatitis may also occur. Pyrethrins can
cause allergic dermatitis and systemic allergic
reactions.
o INHALATION is the major route of exposure, with airway
irritation as the primary toxic effect. Following
inhalation, a stuffy, runny nose and scratchy throat
are common. Hypersensitivity reactions including
wheezing, sneezing, shortness of breath and
bronchospasm may be noted.
o OCULAR - Eye exposures may result in mild to severe
corneal damage that generally resolves with
conservative care.
o Piperonyl butoxide and other compounds are often added
to pyrethrin insecticides as synergists and may
contribute to toxicity.
o Synthetic pyrethroids, which are related to pyrethrins,
are covered in a separate management.
HEENT
0.2.4.1 ACUTE EXPOSURE
o A stuffy, runny nose and scratchy throat following
inhalational exposure may be noted.
o Eye exposures may result in mild to severe corneal
damage, decreased visual acuity and periorbital edema.
CARDIOVASCULAR
0.2.5.1 ACUTE EXPOSURE
o Hypotension and tachycardia, associated with
anaphylaxis, may occur.
RESPIRATORY
0.2.6.1 ACUTE EXPOSURE
o Hypersensitivity reactions characterized by
pneumonitis, cough, dyspnea, wheezing, chest pain, and
bronchospasm may occur. Rare cases of respiratory
failure and cardiopulmonary arrest have been reported.
NEUROLOGIC
0.2.7.1 ACUTE EXPOSURE
o Paresthesias, headaches, and dizziness are common.
Massive exposure may result in hyperexcitability and
seizures, but this is rare.
GASTROINTESTINAL
0.2.8.1 ACUTE EXPOSURE
o Nausea, vomiting and abdominal pain commonly occur and
develop within 10 to 60 minutes following ingestion.
DERMATOLOGIC
0.2.14.1 ACUTE EXPOSURE
o Irritant and contact dermatitis may develop. Erythema
which mimics sunburn has also been noted after
prolonged repeated exposure.
ENDOCRINE
0.2.16.1 ACUTE EXPOSURE
o Type I motor symptoms following severe poisoning may
result in sympathetic activation.
IMMUNOLOGIC
0.2.19.1 ACUTE EXPOSURE
o Sudden bronchospasm, swelling of oral and laryngeal
mucous membranes, and anaphylactoid reactions have been
reported after pyrethrum inhalation. Hypersensitivity
pneumonitis characterized by cough, shortness of
breath, chest pain, and bronchospasm may be noted.
GENOTOXICITY
o Pyrethrum is not mutagenic in bacterial reversion tests
(Ray, 1991).
|
| Laboratory: |
o Pyrethrin plasma levels are not clinically useful or
readily available.
o Monitor for allergic responses such as asthma or contact
dermatitis.
|
| Treatment Overview: |
ORAL EXPOSURE
o There is no specific antidote for pyrethrin poisoning.
Treatment is symptomatic and supportive and includes
monitoring for the development of hypersensitivity
reactions with respiratory distress. Provide adequate
airway management when needed. Gastric decontamination
is usually not required unless the pyrethrin product is
combined with a hydrocarbon.
o ALLERGIC REACTION: MILD: antihistamines with or
without epinephrine. SEVERE: oxygen, aggressive
airway management, antihistamines, epinephrine (ADULT:
0.3 to 0.5 mL of a 1:1000 solution subcutaneously;
CHILD: 0.01 mL/kg; may repeat in 20 to 30 min),
corticosteroids, ECG monitoring, and IV fluids.
INHALATION EXPOSURE
o INHALATION: Move patient to fresh air. Monitor for
respiratory distress. If cough or difficulty breathing
develops, evaluate for respiratory tract irritation,
bronchitis, or pneumonitis. Administer oxygen and
assist ventilation as required. Treat bronchospasm with
beta2 agonist and corticosteroid aerosols.
EYE EXPOSURE
o DECONTAMINATION: Irrigate exposed eyes with copious
amounts of tepid water for at least 15 minutes. If
irritation, pain, swelling, lacrimation, or photophobia
persist, the patient should be seen in a health care
facility.
DERMAL EXPOSURE
o DECONTAMINATION: Remove contaminated clothing and wash
exposed area thoroughly with soap and water. A
physician may need to examine the area if irritation or
pain persists.
o Vitamin E topical application is highly effective in
relieving paresthesias.
|
| Range of Toxicity: |
o The minimal lethal dose of pyrethrum is not established,
but is probably in the range of 10 to 100 grams.
o Hypersensitivity reactions may be noted, especially
following a chronic dermal or inhalation exposure.
Patients with underlying asthma may be predisposed to
severe bronchospastic reactions after exposure.
|
Antidote and Emergency Treatment:
No specific antidote known. Symptomatic treatment.
Treatment is supportive, and most casual exposures require only decontamination.
Topical vitamin E may ameliorate the paresthesias that accompany contact with
synthetic pyrethroids containing an alpha-cyano group (eg, fenvalerate, cypermethrin,
flucythrinate). /Synthetic pyrethroids/
The additives (e.g. petroleum distillate), when present, represent a greater
toxic threat to the patient than the active ingredient itself. ... Emesis should
not be induced when petroleum distillate additives are present unless the product
ingested is estimated to contain a near lethal dose (1 g/kg) of pyrethrum or
pyrethrins. The alert person with an intact gag reflex & a sublethal pyrethrum
ingestion without other toxic constituents may have emesis induced by ipecac,
followed by a saline cathartic & slurry of activated charcoal. ... Pulmonary
& allergic sequelae are treated symptomatically with airway maintenance,
oxygen, & ventilatory assistance as required. Standard drugs and management
protocols may be used for treatment of bronchospasm & anaphylaxis. Seizures
are treated with diazepam. /Pyrethrum and synthetic pyrethroids/
Skin decontamination. Wash skin promptly with soap and water ... . If irritant
or paresthetic effects occur, obtain treatment by a physician. Because volatilization
of pyrethroids apparently accounts for paresthesia affecting the face, strenuous
measures should be taken (ventilation, protective face mask and hood) to avoid
vapor contact with the face and eyes. Vitamin E oil preparations (dL-alpha tocopheryl
acetate) are uniquely effective in preventing and stopping the paresthetic reaction.
They are safe for application to the skin under field conditions. Corn oil is
somewhat effective, but possible side effects with continuing use make it less
suitable. Vaseline is less effective than corn oil. Zinc oxide actually worsens
the reaction. /Pyrethroids/
Eye contamination. Some pyrethroid compounds can be very corrosive to the
eyes. Extraordinary measures should be taken to avoid eye contamination. the
eye should be treated immediately by prolonged flushing of the eye with copious
amounts of clean water or saline. If irritation persists, obtain professional
ophthalmologic care. /Pyrethroids/
Other treatments. Several drugs are effective in relieving the pyrethroid
neurotoxic manifestations observed in deliberately poisoned laboratory animals,
but none has been tested in human poisonings. Therefore, neither efficacy nor
safety under these circumstances is known. Furthermore, moderate neurotoxic
symptoms and signs are likely to resolve spontaneously if they do occur. /Pyrethroids/
Animal Toxicity Studies:
Toxicity Summary:
Metabolic studies have been carried out on /various mammalian species/. In
rats and dogs, cyhalothrin has been shown to be well absorbed after oral administration,
extensively metabolized, and eliminated as polar conjugates in urine. ... Residues
in fats were eliminated with a half-life of 23 days. ... In all mammalian species
investigated, cyhalothrin has been found to be extensively metabolized as a
result of ester cleavage to the cyclopropanecarboxylic acid and 3-phenoxybenzoic
acid, and eliminated as conjugates. In fish, the main residue in tissues consists
of unchanged cyhalothrin, and there are lower levels of the ester cleavage products.
Under laboratory conditions of constant toxicant concentrations, cyhalothrin
and lambda-cyhalothrin are highly toxic to fish and to aquatic invertebrates.
... Accumulation studies conducted under laboratory conditions with constant
concentration show that rapid uptake takes place in fish ... Since the compound
is rapidly absorbed and degraded under natural conditions, there will not be
any practical problems concerning the accumulation of residues or the toxicity
of cyhalothrin or lambda-cyhalothrin in aquatic species. Cyhalothrin and lambda-cyhalothrin
are virtually non-toxic to birds ... Under laboratory conditions, cyhalothrin
and lambda-cyhalothrin are toxic to honey bees ... However, in the field the
hazard is lower ... Cyhalothrin and lambda-cyhalothrin are type II pyrethroids;
clinical signs /of toxicity/ include ataxia, unsteady gait, and hyperexcitability.
In the rabbit, cyhalothrin is a moderate eye irritant and lambda-cyhalothrin
is a mild eye irritant; both are mild skin irritants. /Cyhalothrin/ is a moderate
skin sensitizer in the guinea pig. Lambda-cyhalothrin is not a skin sensitizer.
... Cyhalothrin and lambda-cyhalothrin gave negative results in a range of in
vivo and in vitro assays designed to detect gene mutations, chromosomal damage,
and other genotoxic effects. When orally administered to the rat and rabbit
during the period of major organogenesis, cyhalothrin was neither embryotoxic
or teratogenic at dose levels that elicited maternal toxicity ... In manufacturing,
formulation, laboratory work and field usage, /human/ symptoms of subjective
facial sensation have been reported. ... Subjective facial skin sensations,
which may be experienced by people who handle cyhalothrin and lambda-cyhalothrin
are believed to be brought about by repetitive firing of sensory nerve terminals
in the skin. They may be considered as an early warning signal indicating that
overexposure of the skin has occurred. ... The exposure of the general population
to cyhalothrin and lambda-cyhalothrin is expected to be very low and is not
likely to present a hazard under recommended conditions of use. ... Cyhalothrin
and lambda-cyhalothrin are unlikely to present a hazard to those occupationally
exposed. ... Under laboratory conditions cyhalothrin and lambda-cyhalothrin
are highly toxic to fish, aquatic arthropods, and honey bees. However, under
field conditions, lasting adverse effects are not likely to occur under recommended
conditions of use.
Non-Human Toxicity Excerpts:
The type II pyrethroids /including cyhalothrin/ produce a complex poisoning
syndrome & act on a wide range of tissues. They give sodium tail currents
with relatively long time constants, which may be the reason for their ability
to act on the whole range of excitable tissues. Type II poisoning in rats involves
progressive development of nosing & exaggerated jaw opening similar to that
seen in response to an irritant placed on the tongue, salivation which may be
profuse, incr extensor tone in the hind limbs causing a rolling gait, incoordination
progressing to a very coarse tremor, choreoform movements of the limbs &
tail often precipitated by sensory stimuli, generalized choreoathetosis (writhing
spasms), tonic seizures, apnea, & death. At lower doses more subtle repetitive
behavior is seen. In dogs, similar symptoms are seen but salivation & upper
airway hypersecretion & GI symptoms are more prominent.
Moderate eye irritant; mild skin irritant (rabbits).
No significant toxicological effect observed in feeding trials with rats (2
yr) or dogs (0.5 yr) at 2.5 mg/kg/day.
In a 90-day feeding study in which rats were fed cyhalothrin at dose levels
up to 250 mg/kg diet, reduced body weight gains were observed in males at 250
mg/kg diet. Marginal effects on mean erythrocyte volumes were noted in some
treated groups, as well as some liver changes, which were considered to be an
adaptive response. In a 90-day feeding study in which rats were fed lambdacyhalothrin
at dose levels up to 250 mg/kg diet, reduced body weight gain was observed in
both sexes at 250 mg/kg diet. Some effects on clinical chemistry were observed
as well as liver effects similar to thse noted with cyhalothrin. The no-observed-effect
level was 50 mg/kg diet.
In a 26-week oral study in which cyhalothrin doses of up to 10 mg/kg body
weight per day were administered to dogs, signs of pyrethroid toxicity were
observed at 10 mg per kg body weight per day. The no-observed-effect level was
2.5 mg/kg body weight per day. A similar study was conducted in which up to
3.5 mg lambda-cyhalothrin/kg body weight per day was administered to dogs for
52 weeks. Clinical signs of pyrethroid toxicity (neurological signs) were observed
in all animals dosed with 3.5 mg/kg body weight per day. The no-observed-effect
level was 0.5 mg/kg body weight per day.
When groups of 24 mated female rats (Charles River CD-1) were given cyhalothrin
orally (in corn oil), at 0, 5, 10, or 15 mg/kg body weight per day, from day
6 to 15 inclusive of gestation and were killed on day 20, there was reduced
body weight gain at the highest dose level and evidence of mild pyrethroid toxicity
in two of these animals. There were no other effects on the clinical or litter
parameters attributable to treatment with cyhalothrin, and examination of the
viscera and skeletons showed no effects of treatment. At the highest dose level,
there was maternal toxicity, but there was no effect on any aspect of fetal
development at any dose level.
Groups of 52 male and 52 female Charles River CD-1 mice were maintained for
104 weeks on diets containing 0, 20, 100, or 500 mg cyhalothrin/kg and further
groups of 12 males and 12 females were designated for interim sacrifice after
52 weeks. During the study there were no deaths attributable to treatment with
cyhalothin. Signs of toxicity ascribable to cyhalothrin included piloerection
and hunched posture in both sexes at 500 mg/kg and in males at 100 mg/kg and
reduced body weight gain, higher food intake, and reduced efficiency of food
utilization in males receiving 500 mg/kg. There was statistically significant
increase, compared to the controls, in the incidence of mammary adenocarcinoma
in females at the two highest dose levels. However, the frequency of these tumors
was not unduly at variance with that normally seen in the strain of mouse used,
and no dose relationship was apparent. Thus, there were no neoplastic findings
that could be attributed to the long-term administration of cyhalothrin. There
was a clear NOEL of 20 mg/kg corresponding to a mean calculated daily intake
of 1.8 mg/kg body weight per day in males and 2.0 mg/kg body weight per day
in females.
Cyhalothrin in polyethylene glycol (PEG 300) (10, 100, or 1000 mg/kg body
weight per day) was applied to the skin of groups of 10 male and 10 female New
Zealand White rabbits and kept in contact with the skin 6 hr day, 5 days per
week for 3 weeks (i.e. a total of 15 applications) by means of an occulisve
dressing. A group of 14 male and 14 female control rabbits was treated with
polyethylene glycol (PEG 300) using the same procedure. The skin of half the
animals in each group was abraded prior to the application of cyhalothrin. Repeated
application of the vehicle alone (polyethylne glycol) and the vehicle plus cyhalothrin
caused slight to severe skin irritation. At the highest dose level there was
an increased incidence of edema and erythema. A small number of animals given
the highest dose showed pyrethroid-like symptoms, but only when the skin was
unabraded. The NOEL was considered to be 100 mg/kg/day.
Groups of 72 male and 72 female Alpk/AP strain rats were fed diets containing
cyhalothrin at levels of 0, 10, 50, or 250 mg/kg diet for up to 104 weeks. All
the surviving animals were sacrificed, and histopathological and gross postmortem
examinations were carried out. Decreased body weight gain, accompanied by a
small decrease in food consumption, was evident in rats of both sexes fed the
highest dose. This was accompanied by minor changes in blood biochemistry. Increase
liver weight was seen in rats of both sexes fed cyhalothrin at 250 mg/kg at
the interim sacrifice but this was not evident at termination. There was no
histopathological evidence of a chronic toxic effect due to cyhalothrin. In
particular clinical and histopathological evaluation gave no indication of an
effect on the nervous system. There was no evidence for a carcinogenic effect
of cyhalothrin. The toxicological NOEL for this study was 50 mg cyhalothrin/kg
diet, corresponding to a minimum dose rate of approximately 1.7 mg/kg body weight
per day for male rats and 1.9 mg/kg/day for female rats.
Groups of at least 18 pregnant New Zealand White rabbits received cyhalothrin
orally in corn oil daily at 0, 3, 10, or 30 mg/kg body weight, from days 6 to
18 (inclusive) of gestation and were killed on day 28. There was reduced body
weight gain at the highest dose, accompanied by reduced food intake during dosing.
There were no clinical signs and no changes in pregnancy incidence or in litter
parameters attributable to treatment with cyhalothrin. Examinations of the viscera
and skeletons revealed no effects of treatment. At the highest dose level, there
was maternal toxicity, but there was no effect on any aspect of fetal development
at any dose level.
Five test strains, TA1535, TA1537, TA1538, TA98, and TA100, were employed
to evaluate the mutagenic potential of cyhalothrin using the salmonella reverse
mutation assay of Ames. The assay was conducted in the presence and absence
of metabolic activation (S9 mix) with cyhalothrin at levels up to 2500 ug/plate.
The mean numbers of revertant colonies of Salmonella typhimurium observed in
the five test strains indicated an unequivocal negative response. Lambda-cyhalothrin
at dose levels of up to 5000 ug/plate, both in the presence and absence of metabolic
activation, gave a non-mutagenic response in the same test using the same strains.
A skin sensitization test with cyhalothrin on guinea pigs, using the procedure
of Buehler, indicated that cyhalothrin has skin-sensitizing potential. In guinea
pigs that had been previously induced with undiluted cyhalothrin technical material,
using the Magnusson and Kligman maximization test, a moderate sensitization
response was elicited. When lambda-cyhalothrin was tested for skin sensitization
on guinea pigs, using the maximization procedure of Magnusson and Kligmann,
it was shown to have no sensitization potential.
When cyhalothrin was tested in a modification of the cell culture transformation
test of Styles, using Syrian Hamster kidney cell line BHK21C13, the response
in the presence of metabolic activation was unequivocally negative. In the absence
of metabolic transformation there was an erratic increase in numbers of transformed
colonies together with a poor dose response. These data were not thought to
indicate a significant positive response, and it was concluded that cyhalothrin
does not appear to possess significant cell transforming properties. In addition,
the significance of the results from the BHK cell system is doubtful in view
of the questionable interlaboratory reproducibility of this assay.
The mutagenic potential of lambda-cyhalothrin has been assessed in vitro with
L51787 mouse lymphoma cells, both in the presence and absence of auxiliary metabolic
activation (S9) mix, using dose levels of 125-1000, 2000, and 4000 ug/ml. There
was no increase in mutation frequency either in the presence or absence of S9
mix.
Three groups of male mice were dosed with cyhalothrin by gavage, at dose levels
of 1, 5, or 10 mg/kg daily, for 5 consecutive days. A further group received
the known mutagen cyclophosphamide intraperitoneally at 200 mg/kg daily for
five days. The animals were then mated with groups of females at weekly intervals
for eight weeks. Pregnancy incidence, pre- and post- implantation loss, clinical
condition, body weight, and gross necropsy were assessed. There was no evidence
of an increase in the dominant lethal mutation frequency following treatment.
The NOEL was 10 mg/kg per day. Although these studies showed no clastogenic
or mutagenic effect it is not clear whether sufficiently high dose levels were
used.
Male rats were given a single dose or five consecutive daily doses by gavage
of cyhalothrin at levels of 1.5, 7.5, or 15 mg/kg, and bone marrow samples were
taken and examined for chromosomal abnormalties. The results indicated that
cyhalothrin has no clastogenic potential.
When lambda-cyhalothrin was administered to mice at levels of up to 35 mg/kg
and bone marrow preparations were examined for the formulation of micronuclei
in polychromatic erythrocytes, there was no statistically significant increase
in the frequency of micronuclei, compared to control animals. The positive control
substance, cyclophosphamide, showed the expected response.
Groups of 15 male and 30 female (F0 parents) weaning Alderley Park rats were
fed diets containing 0, 10, 30, or 100 mg cyhalothrin per kg. After 12 weeks,
the animals were mated to produce the first (F1a) litter and subsequently remated
to produce a second (F1b) litter. The breeding programme was repeated with F1
parents selected from the F1b offspring and F2 parents selected from the F2b
offspring. Test diets were fed continuously throughout the study. There were
minor effects on body weight gain of parents from all generations receiving
100 mg/kg, but no clinical signs of neurological effects were seen in either
parents or offspring. No effects of treatment were seen on indices of male and
female fertility, gestation period, live born index, or pup survival. There
was a small reduction in mean total litter weight of the F2 and F3 generations
from rats receiving the highest dose which was attributable to minor decreases
in litter size and a small reduction in weight gain of the pups. No effect was
seen in litters from rats receiving 30 mg/kg. There was no evidence of gross
or histopathological change attributable to the treatment. The reproductive
effects seen in rats receiving the highest dose were of a minor nature. A clear
NOEL of 30 mg/kg (corresponding to a dosage in the range of 1.5 to 1.9 mg/kg
body weight per day) was established.
The physical and behavioral effects of cyhalothrin were studied in rats. Pregnant
Wistar rats were administered 0 or 0.018% cyhalothrin topically throughout pregnancy.
After delivery the neonates were monitored for development of fur, testes descent,
and ear, eye, and vaginal opening. Body weights were recorded on postnatal days
2, 7, 14, and 21. The effects on locomotor activity and inhibitory avoidance
behavior were evaluated on postnatal days 21 and 90. The number of head dips
occurring in a hole board test was recorded on postnatal day 90. Development
of fur and times to testes descent and ear and eye opening were significantly
delayed in cyhalothrin exposed pups. Time to vaginal opening was not affected.
Body wt of cyhalothrin exposed pups were significantly increased at postnatal
days 2, 7, and 14, but not at postnatal day 21. Cyhalothrin did not significantly
affect locomotor activity or inhibitory avoidance behavior. Cyhalothrin exposed
rats had a significantly smaller number of head dips in the hole board test.
The authors conclude that prenatal exposure to cyhalothrin delays development
of fur, eye and ear opening, and testes descent and affects motivational behavior.
The delays induced in fur development and eye and ear opening suggest that cyhalothrin
interferes with maternal or neonatal epidermal growth factor activity. The delay
in testes descent suggests that prenatal cyhalothrin exposure induces changes
in male sexual development.
Synthetic pyrethroids have been shown to be toxic for fish, aquatic arthropods,
and honeybees in laboratory tests. But, in practical usage, no serious adverse
effects have been noticed because of the low rates of application and lack of
persistence in the environment. The toxicity of synthetic pyrethroids in birds
and domestic animals is low. /Synthetic pyrethroids/
The in vitro effects of pyrethroids on the mitogenic responsiveness of murine
splenic lymphocytes to concanavalin A and lipopolysaccharide were determined.
Allethrin was the most potent inhibitor, with effective concn in the range of
1X10-6 to 1.5X10-5 M. The results support the possibility of immune suppression
by pyrethroid exposure. /Pyrethroids/
Following absorption through the chitinous exoskeleton of arthropods, pyrethrins
stimulate the nervous system, apparently by competitively interfering with cationic
conductances in the lipid layer of nerve cells, thereby blocking nerve impulse
transmissions. Paralysis and death follow. /Pyrethrins/
Non-systemic insecticide with contact action. Causes paralysis initially,
with death occurring later. Has some acaricidal activity. /Pyrethrins/
Non-systemic insecticide with contact & stomach action, & repellent
properties. Gives rapid knockdown & long residual activity.
Non-Human Toxicity Values:
LD50 Rat (male) oral 166 mg/kg
LD50 Rat (female) oral 114 mg/kg
LD50 Rabbit oral >1000 mg/kg
LD50 Rat (male) percutaneous 1000-2000 mg/kg
LD50 Rat (female) percutaneous 200-2000 mg/kg
LD50 Rabbit (male) percutaneous >2000 mg/kg
LD50 Rabbit (female) percutaneous >2000 mg/kg
LD50 Rat (male) oral 243 mg/kg
LD50 Rat (female) oral 144 mg/kg
LD50 Mouse (male) oral 36.7 mg/kg
LD50 Mouse (female) oral 62.3 mg/kg
LD50 Guinea pig (male) oral >5000 mg/kg
LD50 Rabbit (female) oral >1000 mg/kg
LC50 Rat inhalation 83 mg/cu m/4 hr
Ecotoxicity Values:
LC50 Rainbow trout 0.00054 mg/l/96 hr /Conditions of bioassay not specified/
LD50 Mallard duck oral >5000 mg/kg
LC50 Salmo gairdneri (Rainbow trout) (weight= 0.32.1.37 g) @ 12 deg C 0.54
ug/l/96 hr /Technical cyhalothrin dispersed via acetone/
LC50 Cyprinus Carpio (Carp) (weight= 5.2 g) @ 25-35 deg C, 1.34 ug/l/72 hr
/Technical cyhalothrin dispersed via dimethylformamide/
LC50 Lepomis macrochirus (Bluegill sunfish) (weight= 0.23-0.04 g) @ 22 deg
C, 0.46 ug/l/96 hr /Technical cyhalotrin dispersed via acetone/
LC50 Daphnia Pulex (stage < 24 hr). Static system @ 20 deg C, 160 ng/l/
48 hr /Cyhalotrin 5% WP/
LC50 Daphnia magna (stage 12 h), Static system @ 20 deg C, 380 mg/l/48 hr
/Technical cyhalothrin/
Metabolism/Pharmacokinetics:
Metabolism/Metabolites:
In common with other structurally related pyrethroids, the main routes of
metabolism of cyhalothrin in the cow have been found to be similar to those
observed in rats and dogs, i.e cleavage of the ester bond with subsequent excretion
of the cyclopropyl carboxylic moiety, either free, hydroxylated, or as a glucuronide
conjugate. The phenoxybenzyl moiety was further metabolized by loss of the nitrile
group and excreted as free 3-phenoxybenzoic acid and its amino acid conjugate,
or after aromatic hydroxylation probably at the 4'position. Cyhalothrin itself
gives rise to residues in fats; this is consistent with lipophilic properties
of cyhalothrin compared to those of its more polar metabolites.
Identification of the metabolites produced in the rat studies revealed that,
following oral administration, unabsorbed cyhalothrin was eliminated unchanged
via the feces. The absorbed material was rapidly and extensively metabolized
and no unchanged cyhalothrin was present in urine or bile. The main route of
metabolism was, as anticipated, via hydrolysis of the ester linkage. The cyclopropanecarboxylic
acid moiety was subsequently excreted via the urine as the glucuronide conjugate.
This material accounted for about 50% of the radioactivity in urine following
dosing with (14)C-cyclopropyl-labelled cyhalothrin. The 3-phenoxybenzyl moiety
was further metabolized by loss of the nitrile group, oxidation of the aldehyde
formed to a carboxylic acid, aromatic hydroxylation at the 4'-position, and
formation of the 4-O-sulfate conjugate of 3-(4-hydroxyphenoxy)benzoic acid.
This conjugate accounted for approximately 75% of the urinary radioactivity
following dosing with (14)C-benzyl-labelled cyhalothrin. No metabolite containing
the ester function was detected.
The main route of metabolism after oral administration is, as in the rat,
via cleavage of the ester bond. After intravenous administration (0.1 mg/kg
body weight), the patterns of metabolites in urine were very similar to those
seen in the oral studies. Very little unchanged compound was present in the
feces or urine. The phenoxybenzyl moiety was further metabolized as in the rat;
the main metabolites were N-(3-phenoxybenzyl) glycine, 3-(4-hydroxyphenoxy)benzoic
acid and its sulfate conjugate, 3-phenoxybenzoyl glucuronide, and a little free
3-phenoxybenzoic acid. Other conjugated metabolites were also present. The cyclopropane
acid moiety was extensively metabolized to produce 11 metabolites. These included
the cyclopropane acid glucuronide and other conjugated metabolites. Thus, the
metabolism of cyhalothrin is dominated by cleavage of the ester bond. Subsequent
metabolism of the products is similar both to that of other pyrethroids and
to the fate of cyhalothrin in other species.
The relative resistance of mammals to the pyrethroids is almost wholly attributable
to their ability to hydrolyze the pyrethroids rapidly to their inactive acid
& alcohol components, since direct injection into the mammalian CNS leads
to a susceptibility similar to that seen in insects. Some additional resistance
of homeothermic organisms can also be attributed to the negative temperature
coefficient of action of the pyrethroids, which are thus less toxic at mammalian
body temperatures, but the major effect is metabolic. Metabolic disposal of
the pyrethroids is very rapid, which means that toxicity is high by the iv route,
moderate by slower oral absorption, & often unmeasureably low by dermal
absorption. /Pyrethroids/
FASTEST BREAKDOWN IS SEEN WITH PRIMARY ALCOHOL ESTERS OF TRANS-SUBSTITUTED
ACIDS SINCE THEY UNDERGO RAPID HYDROLYTIC & OXIDATIVE ATTACK. FOR ALL SECONDARY
ALCOHOL ESTERS & FOR PRIMARY ALCOHOL CIS-SUBSTITUTED CYCLOPROPANECARBOXYLATES,
OXIDATIVE ATTACK IS PREDOMINANT. /PYRETHROIDS/
Pyrethrins are reportedly inactivated in the GI tract following ingestion.
In animals, pyrethrins are rapidly metabolized to water soluble, inactive compounds.
/Pyrethrins/
Synthetic pyrethroids are generally metabolized in mammals through ester hydrolysis,
oxidation, and conjugation, and there is no tendency to accumulate in tissues.
In the environment, synthetic pyrethroids are fairly rapidly degraded in soil
and in plants. Ester hydrolysis and oxidation at various sites on the molecule
are the major degradation processes. /Synthetic pyrethroids/
Absorption, Distribution & Excretion:
In rats, following oral admin, cyhalothrin is rapidly eliminated in urine
& feces. The ester group is hydrolyzed, both moieties forming polar conjugates.
After twice daily oral ingestion fo (14)C-benzyl- or (14)C-cyclopropyl-labelled
cyhalothrin (1 mg/kg/day for 7 days), absorption of the insecticide by cows
was apparently slow and incomplete. Approximately 50% of the dosed radioactivity
was excreted in the feces, mainly as unchanged cyhalothrin, but only small amounts
were detected in the bile. With both labelled forms, most of the radioactive
material was rapidly eliminated in the urine (27%) and feces (49%) within 24
hr of each daily dose. Only a very small proportion of the dose was secreted
in the milk (0.8%) and this was found to be unchanged cyhalothrin. Tissue residues
of radioactive material were low and were in the following order: fats> liver>
blood> muscle. Residues in fat consisted of unchanged cyhalothrin. The liver
and kidney contained small amounts of cyhalothrin, but the residues were largely
due to a number of ester-cleavage metabolites that were probably present because
the animals were still actively metabolizing and eliminating a significant fraction
of the most recent day's intake of cyhalothrin. The almost two-fold difference
in the plasma levels of total radiolabelled components obtained with the different
labelled forms suggests that little cyhalothrin was present in blood. The ester
link must therefore be hydrolysed very rapidly, apart from a small fraction
that is distributed into fatty tissues.
The absorption,distribution, excretion, and metabolism of cyhalothrin have
been studied in the dog using cyhalothrin labelled either in the acid (14)C-cyclopropyl
or alcohol (14)C-benzyl moieties of the molecule. Groups of three male and three
female beagle dogs were given a single oral dose of cyhalothrin (1 mg/kg or
10 mg/kg) and, after a 3-week interval, a further single intravenous administration
of 0.1 mg/kg. Samples of blood and excreta were collected for 7 days after dosing
and were analysed for total radioactivity. The proportions of unchanged cyhalothrin
and of metabolites in urine and feces were determined by thin-layer chromatography.
The identity of major metabolites was confirmed by mass spectrometry. The absorption
of cyhalothrin after oral administration was variable. The degree of absorption
was difficult to assess but was within the range 48%-80%. Excretion of radioactivity
after both oral and intravenous dosing was initially rapid, with most of the
administered radioactivity being excreted in the first 48 hr after dosing. After
7 days, a mean of 82-93% had been excreted.
Groups of six male and six female Alderly Park rats received a single oral
dose (1 or 25 mg/kg) of radiolabelled cyhalothrin in corn oil. As it was known
that the metabolism of related poyrethroids involves extensive cleavage of the
ester bond, duplicate experiments were performed using two forms of cyhalothrin
labelled with (14)C in the acid (14)C-cyclopropyl or alcohol (14C-benzyl) portions
of the ester. ... Following oral administration of cyhalothrin, absorption was
variable but accounted for about 55% of the dose. The proportions absorbed were
similar at both dose levels. Excretion was rapid for both (14)C-cyclopropyl-
and (14)C-benzyl- labelled cyhalothrin at both dose levels, although excretion
rates were faster with the (14)C-benzyl label than with the (14)C-cyclopropyl
label. Urinary excretion accounted for approximately 20-40% of the dose and
fecal excretion for 40-65% of the dose during the first 7 days. Peak blood concentrations
of radioactivity were reached within 4-7 hr, and by 48 hr these concentrations
had declined to 10% or less of peak values. A small proportion of an oral dose
(2-3%) was retained in the animals after seven days; analysis of twelve different
tissues indicated that this radioactivity was present mainly in white fat.
Results from a study in which rats were dosed subcutaneously indicated that
some of the dose was excreted via the bile.
To study the excretion and tissue accumulation of cyhalothrin (1 mg/kg/day
by gavage), groups of six male and six female rats received daily doses of (14)C-benzyl-labelled
or (14)C-cyclopropyl-labelled cyhalothrin for 14 days. Urine and fecal samples
were collected every 24 hr up to 7 days after the final dose. Groups of animals
were killed 2, 5, and 7 days after the final dose and a range of tissues were
removed for measurement of residual radioactivity. Fat samples were analysed
by HPLC for unchanged cyhalothrin. The results demonstrated that the excretion
of (14)C-material after multiple oral dosing was similar to that which followed
a single dose. Slightly higher overall excretion in urine (up to 50% of the
administered dose) was probalbly due to more consistent oral absorption in this
study. A large proportion of the oral dose of cyhalothrin was rapidly eliminated
from the body. Analysis of tissue residues revealed that the small proportion
(< 5%) of the dose retained in white fat was unchanged cyhalothrin, which
was eliminated from this tissue with a half-life of about 23 days.
To explore the retention, in fat, of cyhalothrin and lambda-cyhalothrin, groups
of male rats received daily oral doses of (14)C-cyclopropyl-labelled cyhalothrin
(1 mg/kg/day) for up to 119 days. ... Levels of radioactivity in the blood remained
fairly constant and low (approximately 0.2 ug cyhalothrin equivalents per g)
throughout the dosing period. In the liver and kidney, the radioactivity reached
a plateau, after approximately 70 days, at a level corresponding to approximately
2.5 ug cyhalothrin equivalents per g liver and 1.2 ug/g kidney. The concentration
of cyhalothrin in fat at the end of the dosing period was approximately 10 ug/g.
After the cesstation of dosing, levels of radioactivity in the liver, kidney,
and blood declined rapidly. In fat, the levels declined more slowly with an
elimination half-life of 30 days. The radioactive material in fat was unchanged
cyhalothrin; the ratio of enantiomeric pairs, one of which was lambdacyhalothrin,
was not significantly different from that in the dosing solution, indication
that the rate of metabolism of lambda-cyhalothrin was the same as cyhalothrin
and that there was no preferential accumulation of lambda-cyhalothrin.
A comparison ofthe absorption, distribution, excretion, and metabolism of
lambda-cyhalothrin and cyhalotrhin was made to establish whether the single
enantiomer pair lambda-cyhalothrin differed form cyhalothrin (a 50:50 mixture
of lambda-cyhalothrin and the opposite enantiomer pair A). One group of four
male rats given a single oral dose of (14)C-cyclopropyl-labelled lambda-cyhalothrin
(1 mg/kg); a second group of four male rats was given (14)C-cyclopropyl-labelled
lambda-cyhalothrin (1 mg/kg) plus the unlabelled enantiomeric pair A (1 mg/kg);
and a third group of four male rats was given a single oral dose of a 50:50
mixture of (14)C-cyclopropyl-labelled lambda-cyhalothrin and (14)C-labelled
enantiomeric pair A (ie (14)C- cyclopropyl-labelled cyhalothrin at 1 mg/kg).
The urinary and faecal excretion of radioactivity was monitored in all three
groups for three days and the residual radioactivity was then determined in
selected tissues. The metabolite profile of the excreta was determined by thin-layer
chromatography. The results of this study indicate that co-administration of
enantiomer pair A with lambda-cyhalothrin had little or no effect upon the absorption,
distribution, or tissue retention of radioactivity, and there was no effect
upon the metabolite profile of lambda-cyhalothrin. Similarly, the absorption,
distribution, excretion, and metabolism of cyhalothrin was indistinguishable
from that of lambda-cyhalothrin.
Carp were maintained in a flow-through water system containing (14)C-cyclopropyl-labelled
cyhalothrin (at a level of 20 ng/g) for 28 days. Results showed that radioactive
residues in muscle, head, and viscera were 0.035, 0.050, and 0.115 mg/kg, respectively.
The major part of the (14)C-residue (50-65%) was characterized as cyhalothrin.
/PYRETHROIDS/ READILY PENETRATE INSECT CUTICLE AS SHOWN BY TOPICAL LD50 TO
PERIPLANETA (COCKROACH) ... /PYRETHROIDS/
WHEN RADIOACTIVE PYRETHROID IS ADMIN ORALLY TO MAMMALS, IT IS ABSORBED FROM
INTESTINAL TRACT OF THE ANIMALS & DISTRIBUTED IN EVERY TISSUE EXAMINED.
EXCRETION OF RADIOACTIVITY IN RATS ADMIN TRANS-ISOMER: DOSAGE: 500 MG/KG; INTERVAL
20 DAYS; URINE 36%; FECES 64%; TOTAL 100%. /PYRETHROIDS/
Pyrethrins are absorbed through intact skin when applied topically. When animals
were exposed to aerosols of pyrethrins with piperonyl butoxide being released
into the air, little or none of the combination was systemically absorbed. /Pyrethrins/
Mechanism of Action:
The synthetic pyrethroids delay closure of the sodium channel, resulting in
a sodium tail current that is characterized by a slow influx of sodium during
the end of depolarization. Apparently the pyrethroid molecule holds the activation
gate in the open position. Pyrethroids with an alpha-cyano group (e.g., fenvalerate)
produce more prolonged sodium tail currents than do other pyrethroids (e.g.,
permethrin, bioresmethrin). The former group of pyrethroids causes more cutaneous
sensations than the latter. /Synthetic pyrethroids/
Interaction with sodium channels is not the only mechanism of action proposed
for the pyrethroids. Their effects on the CNS have led various workers to suggest
actions via antagonism of gamma-aminobutyric acid (GABA)-mediated inhibition,
modulation of nicotinic cholinergic transmission, enhancement of noradrenaline
release, or actions on calcium ions. Since neurotransmitter specific pharmacological
agents offer only poor or partial protection against poisoning, it is unlikely
that one of these effects represents the primary mechanism of action of the
pyrethroids, & most neurotransmitter release is secondary to incr sodium
entry. /Pyrethroids/
The symptoms of pyrethrin poisoning follow the typical pattern ... : (1) excitation,
(2) convulsions, (3) paralysis, and (4) death. The effects of pyrethrins on
the insect nervous system closely resemble those of DDT, but are apparently
much less persistent. Regular, rhythmic, and spontaneous nerve discharges have
been observed in insect and crustacean nerve-muscle preparations poisoned with
pyrethrins. The primary target of pyrethrins seems to be the ganglia of the
insect central nervous system although some pyrethrin-poisoning effect can be
observed in isolated legs. /Pyrethrins/
Electrophysiologically, pyrethrins cause repetitive discharges and conduction
block. /Pyrethrins/
The interaction of a series of pyrethroid insecticides with the sodium channels
in myelinated nerve fibers of the clawed frog, Xenopus laevis, was investigated
using the voltage clamp technique. Of 11 pyrethroids, 9 insecticidally active
cmpd induced a slowly decaying sodium tail current on termination of a step
depolarization, whereas the sodium current during depolarization was hardly
affected. /Pyrethroids/
Mode of action of pyrethrum & related cmpd has been studied more in insects
& in other invertebrates than in mammals. This action involves ion transport
through the membrane of nerve axons &, at least in invertebrates & lower
vertebrates, it exhibits a negative temperature coefficient. In both of these
important ways & in many details, the mode of action of pyrethrin &
pyrethroids resembles that of DDT. Esterases & mixed-function oxidase system
differ in their relative importance for metabolizing different synthetic pyrethroids.
The same may be true of the constituents of pyrethrum, depending on strain,
species, & other factors. /Pyrethrins and pyrethroids/
The interactions of natural pyrethrins and 9 pyrethroids with the nicotinic
acetylcholine (ACh) receptor/channel complex of Torpedo electronic organ membranes
were studied. None reduced (3)H-ACh binding to the receptor sites, but all inhibited
(3)H-labeled perhydrohistrionicotoxin binding to the channel sites in presence
of carbamylcholine. Allethrin inhibited binding noncompetitively, but (3H)-labeled
imipramine binding competitively, suggesting that allethrin binds to the receptor's
channel sites that bind imipramine. The pyrethroids were divided into 2 types
according to their action: type A, which included allethrin, was more potent
in inhibiting (3)H-H12-HTX binding and acted more rapidly. Type B, which included
permethrin, was less potent and their potency increased slowly with time. The
high affinities that several pyrethroids have for this nicotinic ACh receptor
suggest that pyrethroids may have a synaptic site of action in addition to their
well known effects on the axonal channels. /Pyrethrins and Pyrethroids/
The primary target site of pyrethroid insecticides in the vertebrate nervous
system is the sodium channel in the nerve membrane. Pyrethroids without an alpha-cyano
group (allethrin, d-phenothrin, permethrin, and cismethrin) cause a moderate
prolongation of the transient increase in sodium permeability of the nerve membrane
during excitation. This results in relatively short trains of repetitive nerve
impulses in sense organs, sensory (afferent) nerve fibers, and, in effect, nerve
terminals. On the other hand the alpha-cyano pyrethroids cause a long lasting
prolongation of the transient increase in sodium permeability of the nerve membrane
during excitation. This results in long-lasting trains of repetitive impulses
in sense organs and a frequency-dependent depression of the nerve impulse in
nerve fibers. The difference in effects between permethrin and cypermethrin,
which have identical molecular structures except for the presence of an alpha-cyano
group on the phenoxybenzyl alcohol, indicates that it is this alpha-cyano group
that is responsible for the long-lasting prolongation of the sodium permeability.
Since the mechanisms responsible for nerve impulse generation and conduction
are basically the same throughout the entire nervous system, pyrethroids may
also induce repetitive activity in various parts of the brain.
The difference in symptoms of poisoning by alpha-cyano pyrethroids, compared
with the classical pyrethroids, is not necessarily due to an exclusive central
site of action. It may be related to the long-lasting repetitive activity in
sense organs and possibly in other parts of the nervous system, which, in a
more advance state of poisoning, may be accompanied by a frequency-dependent
depression of the nervous impulse. /Synthetic pyrethroids/
Pyrethroids also cause pronounced repetitive activity and a prolongation of
the transient increase in sodium permeability of the nerve membrane in insects
and other invertebrates. Available information indicates that the sodium channel
in the nerve membrane is also the most important target site of pyrethroids
in the invertebrate nervous system. /Synthetic pyrethroids/
In the electrophysiological experiments using giant axons of cray-fish, the
Type II pyrethroids retain sodium channels in a modified continuous open state
persistently, depolarize the membrane, and block the action potential without
causing repetitive firing. /Pyrethroids type II/
Interactions:
/Pyrethroid/ detoxification ... important in flies, may be delayed by the
addition of synergists ... organophosphates or carbamates ... to guarantee a
lethal effect. ... /Pyrethroid/
Piperonyl butoxide potentiates /insecticidal activity/ of pyrethrins by inhibiting
the hydrolytic enzymes responsible for pyrethrins' metabolism in arthropods.
When piperonyl butoxide is combined with pyrethrins, the insecticidal activity
of the latter drug is increased 2-12 times /Pyrethrins/
At dietary level of 1000 ppm pyrethrins & 10000 ppm piperonyl butoxide
... /enlargement, margination, & cytoplasmic inclusions in liver cells of
rats/ were well developed in only 8 days, but ... were not maximal. Changes
were proportional to dosage & similar to those produced by DDT. Effects
of the 2 ... were additive. /Pyrethrins/
Pharmacology:
Therapeutic Uses:
Pyrethrins with piperonyl butoxide are used for topical treatment of pediculosis(lice
infestations). Combinations of pyrethrins with piperonyl butoxide are not effective
for treatment of scabies (mite infestations). Although there are no well-controlled
comparative studies, many clinicians consider 1% lindane to be pediculicide
of choice. However, some clinicians recommend use of pyrethrins with piperonyl
butoxide, esp in infants, young children, & pregnant or lactating women
... . If used correctly, 1-3 treatments ... are usually 100% effective ... Oil
based (eg, petroleum distillate) combinations ... produce the quickest results.
... For treatment of pediculosis, enough gel, shampoo, or solution ... should
be applied to cover affected hair & adjacent areas ... After 10 min, hair
is ... washed thoroughly ... treatment should be repeated after 7-10 days to
kill any newly hatched lice. /Pyrethrins/
Interactions:
/Pyrethroid/ detoxification ... important in flies, may be delayed by the
addition of synergists ... organophosphates or carbamates ... to guarantee a
lethal effect. ... /Pyrethroid/
Piperonyl butoxide potentiates /insecticidal activity/ of pyrethrins by inhibiting
the hydrolytic enzymes responsible for pyrethrins' metabolism in arthropods.
When piperonyl butoxide is combined with pyrethrins, the insecticidal activity
of the latter drug is increased 2-12 times /Pyrethrins/
At dietary level of 1000 ppm pyrethrins & 10000 ppm piperonyl butoxide
... /enlargement, margination, & cytoplasmic inclusions in liver cells of
rats/ were well developed in only 8 days, but ... were not maximal. Changes
were proportional to dosage & similar to those produced by DDT. Effects
of the 2 ... were additive. /Pyrethrins/
Environmental Fate & Exposure:
Environmental Fate/Exposure Summary:
Cyhalothrin's production and use as an insecticide is expected to result in
its direct release to the environment. If released to air, a vapor pressure
of 7.5X10-9 mm Hg at 20 deg C indicates cyhalothrin will exist solely in the
particulate phase in the ambient atmosphere. Particulate-phase cyhalothrin will
be removed from the atmosphere by wet and dry deposition. If released to soil,
cyhalothrin is expected to have no mobility based upon an estimated Koc of 120,000.
Volatilization from moist soil surfaces may be an important fate process based
upon an estimated Henry's Law constant of 1.5X10-6 atm-cu m/mole. However, adsorption
to soil is expected to attenuate volatilization. Cyhalothrin is not expected
to volatilize from dry soil surfaces based upon its vapor pressure. In soil,
biodegradation half-lives have been found to range between 4 and 12 weeks. If
released into water, cyhalothrin is expected to adsorb to suspended solids and
sediment based upon its estimated Koc. Volatilization from water surfaces may
be an important fate process based upon this compound's estimated Henry's Law
constant. Estimated volatilization half-lives for a model river and model lake
are 35 and 400 days, respectively. However, volatilization from water surfaces
is expected to be attenuated by adsorption to suspended solids and sediment
in the water column. The volatilization half-life from a model pond is about
630 years when adsorption is considered. An estimated BCF of 770 suggests the
potential for bioconcentration in aquatic organisms is high. Base-catalyzed
second-order hydrolysis half-lives of 36 and 4 years were estimated for pH values
of 7 and 8, respectively. Occupational exposure to cyhalothrin may occur through
inhalation and dermal contact with this compound at workplaces where cyhalothrin
is produced or used. Monitoring data indicate that the general population may
be exposed to cyhalothrin via ingestion of food containing residues of this
compound. (SRC)
Probable Routes of Human Exposure:
Occupational exposure to cyhalothrin may occur through inhalation of dust
and dermal contact with this compound at workplaces where cyhalothrin is produced
or used. Monitoring data indicate that the general population may be exposed
to cyhalothrin via ingestion of food containing residues of this compound. (SRC)
Artificial Pollution Sources:
Cyhalothrin's production and use as an insecticide(1) is expected to result
in its direct release to the environment(SRC).
Environmental Fate:
TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value
of 120,000(SRC), determined from a measured log Kow of 6.8(2) and a regression-derived
equation(3), indicates that cyhalothrin is expected to be immobile in soil(SRC).
Volatilization of cyhalothrin from moist soil surfaces may be an important fate
process(SRC) given an estimated Henry's Law constant of 1.5X10-6 atm-cu m/mole(SRC),
determined from its vapor pressure, 7.5X10-9 mm Hg at 20 deg C(2), and water
solubility, 0.005 mg/l(4). Cyhalothrin is not expected to volatilize from dry
soil surfaces(SRC) based upon a vapor pressure of 7.5X10-9 mm Hg(2). In soil,
biodegradation half-lives range between 4 to 12 weeks(2). Degradation products
are rapidly mineralized to carbon dioxide. Leaching of cyhalothrin and its degradation
products through a range of soil types is negligible(2).
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value
of 120,000(SRC), determined from a measured log Kow of 6.8(2) and a regression-derived
equation(3), indicates that cyhalothrin is expected to adsorb to suspended solids
and sediment(SRC). Volatilization from water surfaces may occur(3) based upon
an estimated Henry's Law constant of 1.5X10-6 atm-cu m/mole(SRC), determined
from its vapor pressure, 7.5X10-9 mm Hg at 20 deg C(2), and water solubility,
0.005 mg/l(4). Using this Henry's Law constant and an estimation method(3),
volatilization half-lives for a model river and model lake are 35 and 390 days,
respectively(SRC). However, volatilization from water surfaces is expected to
be attenuated by adsorption to suspended solids and sediment in the water column(SRC).
Photodegradation of cyhalothrin in light was <10% after 1.67 years(2). According
to a classification scheme(5), an estimated BCF of 770(SRC), from its log Kow
of 6.8(2) and a regression-derived equation(6), suggests the potential for bioconcentration
in aquatic organisms is high(SRC). Although environmental biodegradation data
specific to cyhalothrin are not available, the pyrethroid class of insecticides
is readily degraded by environmental organisms(7,8); based upon its structure,
cyhalothrin is also expected to readily biodegrade in aquatic environments(7,8).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile
organic compounds in the atmosphere(1), cyhalothrin, which has a vapor pressure
of 7.5X10-9 mm Hg at 20 deg C(2), will exist solely in the particulate phase
in the ambient atmosphere. Particulate-phase cyhalothrin may be removed from
the air by wet and dry deposition(SRC).
Environmental Biodegradation:
Biodegradation half-lives for cyhalothrin have been found to range between
4-12 weeks(1). Although no additional environmental biodegradation data specific
to cyhalothrin were found, the pyrethroid class of insecticides is degraded
readily by environmental organisms(2,3); based upon its structure, cyhalothrin
is also expected to biodegrade readily(2,3).
Environmental Abiotic Degradation:
A base-catalyzed second-order hydrolysis rate constant of 0.006 L/mole-sec(SRC)
was estimated using a structure estimation method(1); this corresponds to half-lives
of 36 and 4 years at pH values of 7 and 8, respectively(1). No decomposition
or change in the cis/trans ratios occurred in the dark after 4 years at 50 deg
C(2). Loss of cyhalothrin in the light was <10% after 1.67 years(2). Hydrolysis
in water is slow at pHs of 7-9 but is more rapid at a pH of 9(2). Solution and
solid phase photodecomposition of cyhalothrin with the chloro(trifluoromethyl)vinyl
substituent involves cis/trans isomerization reactions and free-radical processes
leading to decarboxylation, ester cleavage, proton abstraction, oxygen scavenging,
and reactions with solvent generated radicals(3). Similar results are obtained
in hydrocarbon solvents, aqueous acetonitrile anionic and cationic micelles,
and on glass and soil surfaces(3).
Environmental Bioconcentration:
An estimated BCF of 770 was calculated for cyhalothrin(SRC), using a log Kow
of 6.8(1) and a regression-derived equation(2). According to a classification
scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms
is high(SRC). Concentrations of DOC (Aldrich humic acid) as low as 3.1 mg/l
resulted in a significant decrease in bioaccumulation using Daphnia magna from
3.8% accumulation with 1.3 mg/l DOC to 20% accumulation with 3.1 mg/l DOC(4).
Soil Adsorption/Mobility:
The Koc of cyhalothrin is estimated as 120,000(SRC), using a measured log
Kow of 6.8(1) and a regression-derived equation(2). According to a classification
scheme(3), this estimated Koc value suggests that cyhalothrin is expected to
be immobile in soil.
Volatilization from Water/Soil:
The Henry's Law constant for cyhalothrin is estimated as 1.5X10-6 atm-cu m/mole(SRC)
based upon its vapor pressure, 7.5X10-9 mm Hg(1), and water solubility, 0.005
mg/l(2). This Henry's Law constant indicates that cyhalothrin may volatilize
from water surfaces(3). Based on this Henry's Law constant, the volatilization
half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3
m/sec)(3) is estimated as 35 hours(SRC). The volatilization half-life from a
model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(3) is
estimated as 390 days(SRC). However, volatilization from water surfaces is expected
to be attenuated by adsorption to suspended solids and sediment in the water
column. The estimated volatilization half-life from a model pond is 630 years
if adsorption is considered(4). Cyhalothrin's estimated Henry's Law constant
indicates that volatilization from moist soil surfaces may occur(SRC). Cyhalothrin
is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor
pressure of 7.5X10-9 mm Hg(1).
Food Survey Values:
Cyhalothrin residues have been detected in domestic apples (16 out of 2,464
samples) at a maximum concn of 0.4 ppm, imported apples (6 out of 735 samples)
at a maximum concn of 0.50 ppm, domestic pears (14 out of 571 samples) at a
maximum concn of 0.4 ppm, imported pears (5 out of 816 samples) at a maximum
concn of 0.5 ppm, and imported oranges (4 out of 474 samples) at a maximum concn
of 0.5 ppm in a survey of domestic and imported foods which may be eaten by
infants/children during 1985-1991(1). Cyhalothrin concns were measured by means
of capillary gas chromatography using extraction with ethyl acetate and dichloromethane
from an assortment of vegetable and fruit samples(2). Cyhalothrin concns ranged
from 68.2 to 91.6 ppm for those samples measured with ethyl acetate extraction(2),
while concns ranged from 61.2 to 94 ppm for those samples measured with dichloromethane
extraction(2). Cyhalothrin was detected, concn unreported, in one out of 18
dried bean samples in the 1995-1996 Danish National Pesticide Monitoring Program(3).
The compound was detected at an avg concn of 0.07 ug/g in peas from farms in
Delhi, India during 1992-93(4).
Environmental Standards & Regulations:
Acceptable Daily Intakes:
OPP RfD= 0.005 mg/kg; EPA RfD= 0.005 mg/kg; WHO RfD= 0.02 mg/kg
Chemical/Physical Properties:
Molecular Formula:
C23-H19-Cl-F3-N-O3
Molecular Weight:
449.86
Color/Form:
Viscous liquid yellow-brown
Odor:
Mild
Boiling Point:
187-190 deg C @ 0.2 mm Hg
Melting Point:
Below 10 deg C
Density/Specific Gravity:
1.25 @ 25 deg C
Octanol/Water Partition Coefficient:
log Kow = 6.8
Solubilities:
In acetone, dichloromethane, methanol, diethyl ether, ethyl acetate, hexane,
toluene, all >500 g/l at 20 deg C.
In water, 5.0X10-3 mg/l, temp not specified.
Spectral Properties:
Index of refraction: 1.534 at 24 deg C/D
Vapor Pressure:
7.5X10-9 mm Hg @ 20 deg C
Other Chemical/Physical Properties:
Yellow to brown viscous oil /Technical cyhalothrin/
Decomposes at 275 deg C
Chemical Safety & Handling:
Skin, Eye and Respiratory Irritations:
Immediately irritating to the eye. /Pyrethrins/
The chief effect from exposure ... is skin rash particularly on moist areas
of the skin. ... May irritate the eyes. /Pyrethroids/
Fire Fighting Procedures:
Use carbon dioxide, foam, or dry chemical /on fires involving pyrethroids/.
/Pyrethrum/
Fire-fighting: Self-contained breathing apparatus with a full facepiece operated
in pressure-demand or other positive-pressure mode. /Pyrethrum/
Extinguish fire using agent suitable for type of surrounding fire. /Pyrethrins/
Explosive Limits & Potential:
An explosive.
Hazardous Reactivities & Incompatibilities:
Incompatibility: Strong oxidizers. /Pyrethrins/
... Incompatible with lime & ordinary soaps because acids & alkalies
speed up processes of hydrolysis. /Pyrethrins/
Slowly hydrolyzed by water in sunlight at pH 7-9, more rapidly at pH >9.
Hazardous Decomposition:
Decomposes at 275 deg C
When heated to decomp it emits toxic vapors of /nitrogen oxides, hydrogen
fluoride, hydrogen chloride/.
Protective Equipment & Clothing:
Employees should be provided with and required to use dust- and splash-proof
safety goggles where /pyrethroids/ ... may contact the eyes. /Pyrethroids/
Employees should be provided with and be required to use impervious clothing,
gloves, and face shields (eight-inch minimum). /Pyrethroids/
Wear appropriate equipment to prevent: Repeated or prolonged skin contact.
/Pyrethrum and pyrethrins/
Wear eye protection to prevent: Reasonable probability of eye contact. /Pyrethrins/
Recommendations for respirator selection. Max concn for use: 50 mg/cu m: Respirator
Classes: Any chemical cartridge respirator with organic vapor cartridge(s) in
combination with a dust, mist, and fume filter. May require eye protection.
Any supplied-air respirator. May require eye protection. Any self-contained
breathing apparatus. May require eye protection. /Pyrethrins/
Recommendations for respirator selection. Max concn for use: 125 mg/cu m:
Respirator Classes: Any supplied-air respirator operated in a continuous flow
mode. May require eye protection. Any powered, air-purifying respirator with
organic vapor cartridge(s) in combination with a dust, mist, and fume filter.
May require eye protection. /Pyrethrins/
Recommendations for respirator selection. Max concn for use: 250 mg/cu m:
Respirator Classes: Any chemical cartridge respirator with a full facepiece
and organic vapor cartridge(s) in combination with a high-efficiency particulate
filter. Any self-contained breathing apparatus with a full facepiece. Any supplied-air
respirator with a full facepiece. Any powered, air-purifying respirator with
a tight-fitting facepiece and organic vapor cartridge(s) in combination with
a high-efficiency particulate filter. May require eye protection. /Pyrethrins/
Recommendations for respirator selection. Max concn for use: 5,000 mg/cu m:
Respirator Class: Any supplied-air respirator with a full facepiece and operated
in a pressure-demand or other positive pressure mode. /Pyrethrins/
Recommendations for respirator selection. Condition: Emergency or planned
entry into unknown concn or IDLH conditions: Respirator Classes: Any self-contained
breathing apparatus that has a full facepiece and is operated in a pressure-demand
or other positive pressure mode. Any supplied-air respirator with a full face
piece and operated in pressure-demand or other positive pressure mode in combination
with an auxiliary self-contained breathing apparatus operated in pressure-demand
or other positive pressure mode. /Pyrethrins/
Recommendations for respirator selection. Condition: Escape from suddenly
occurring respiratory hazards: Respirator Classes: Any air-purifying, full-facepiece
respirator (gas mask) with a chin-style, front- or back-mounted organic vapor
canister having a high-efficiency particulate filter. Any appropriate escape-type,
self-contained breathing apparatus. /Pyrethrins/
Preventive Measures:
SRP: The scientific literature for the use of contact lenses in industry is
conflicting. The benefit or detrimental effects of wearing contact lenses depend
not only upon the substance, but also on factors including the form of the substance,
characteristics and duration of the exposure, the uses of other eye protection
equipment, and the hygiene of the lenses. However, there may be individual substances
whose irritating or corrosive properties are such that the wearing of contact
lenses would be harmful to the eye. In those specific cases, contact lenses
should not be worn. In any event, the usual eye protection equipment should
be worn even when contact lenses are in place.
Skin that becomes contaminated with /pyrethrum/ should be promptly washed
or showered with soap or mild detergent and water. /Pyrethrum/
Clothing contaminated with /pyrethrum/ should be placed in closed containers
for storage until provision is made for the removal of /pyrethrum/ from the
clothing. /Pyrethrum/
Respirators may be used when engineering and work practice controls are not
technically feasible, when such controls are in the process of being installed,
or when they fail or need to be supplemented. Respirators may also be used for
operations which require entry into tanks or closed vessels, and in emergency
situations. /Pyrethrum/
Employees who handle /pyrethrum/ ... should wash their hands thoroughly with
soap or mild detergent and water before eating, smoking, or using toilet facilities.
/Pyrethrum/
Avoid contact with skin. Keep out of any body of water. Do not contaminate
water by cleaning of equipment or disposal of waste. Do not reuse empty container.
Destroy it by perforating or crushing. /Pyrethrum/
Contact lenses should not be worn when working with this chemical. /Pyrethrins/
Workers should wash: Promptly when skin becomes contaminated. /Pyrethrins/
Work clothing should be changed daily: If it is reasonably probable that the
clothing may be contaminated. /Pyrethrins/
Remove clothing: Promptly if it is non-impervious clothing that becomes contaminated.
/Pyrethrins/
SRP: Contaminated protective clothing should be segregated in such a manner
so that there is no direct personal contact by personnel who handle, dispose,
or clean the clothing. Quality assurance to ascertain the completeness of the
cleaning procedures should be implemented before the decontaminated protective
clothing is returned for reuse by the workers. Contaminated clothing should
not be taken home at end of shift, but should remain at employee's place of
work for cleaning.
Stability/Shelf Life:
Stable to decomp & cis-trans isomerization for at least 4 yr in the dark
at 50 deg C. Stable to light; loss on storage in the light is < 10% in 20
months. Decomposes at 275 deg C. Slowly hydrolyzed by water in sunlight at pH
7-9, more rapidly at pH >9.
Pyrethrins ... /are/ stable for long periods in water-based aerosols where
... emulsifiers give neutral water systems. /Pyrethrins/
Storage Conditions:
Pyrethrins with piperonyl butoxide topical preparations should be stored in
well-closed containers at a temperature less than 40 deg C, preferably between
15-30 deg C. /Pyrethrins/
Disposal Methods:
SRP: At the time of review, criteria for land treatment or burial (sanitary
landfill) disposal practices are subject to significant revision. Prior to implementing
land disposal of waste residue (including waste sludge), consult with environmental
regulatory agencies for guidance on acceptable disposal practices.
Occupational Exposure Standards:
Manufacturing/Use Information:
Major Uses:
For Cyhalothrin (USEPA/OPP Pesticide Code: 128867) there are 0 labels match.
/SRP: Not registered for current use in the U.S., but approved pesticide uses
may change periodically and so federal, state and local authorities must be
consulted for currently approved uses./
Insecticide; acaricide
Control of animal ectoparasites, especially Boophilus microplus or Haematobia
irritans on cattle, and Bovicola ovis, Linognathus spp. and Melophagus ovinus
on sheep. Applied as an animal dip or as a spray around animal houses.
Cyhalothrin is a pyrethroid insecticide with a high level of activity (application
rate up to 20 g/ha) against a wide range of Lepidoptera, Hemiptera, Diptera,
and Coleoptera species.
Cyhalothrin has also found uses in public and animal health applications where
it effectively controls a broad spectrum of insects, including cockroaches,
flies, mosquitos, and ticks. It has high activity as a residual spray on inert
surfaces.
MEDICATION
Methods of Manufacturing:
Prepared by esterification of 3-(2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-
dimethylcyclopropanecarboxylic acid chloride with alpha-cyano-3-phenoxybenzyl
alcohol.
Prepn: R. K. Huff, Ger. pat 2,802,962; idem, U.S. pat 4,183,948 (1977, 1980
both to ICI).
General Manufacturing Information:
Synthetic pyrethroid insecticide
Cyhalothrin has two asymmetric centres in the acid moiety and one in the alcohol
moiety, as well as Z and E forms. Thus, there are 16 possible isomeric forms
(eight enantiomeric pairs). However, in practice cyhalothrin is produced only
in the Z and cis forms, reducing the number of isomers to four. These comprise
two cis enantiomeric pairs: Enantiomer pair A: (Z), (1R, 3R), R-a-cyano (Z);
Enantiomer pair B: (Z), )1R, 3R), S-a-cyano (Z), (IS, 3S) R-a-cyano.
/Pyrethroids/ are modern synthetic insecticides similar chemically to natural
pyrethrins, but modified to increase stability in the natural environment. /Pyrethroids/
Formulations/Preparations:
USEPA/OPP Pesticide Code 128867; Trade Names: ICI 146,814, Grenade, R114563,
PP 563.
Emulsifiable concentrate; wettable powder
Tech. grade cyhalothrin has purity greater than/equal to 90%, of which purity
greater than/equal to 95% is cis-isomers.
Commercial product exists as a mixture consisting of 95% cis-isomers
Technical grade cyhalothrin contains more than 90% of the pesticide and is
formulated in 5%, 10%, and 20% emulsifiable concentrates. Technical grade lambda-cyhalothrin
also contains more than 90% active ingredient. It is formulated as 2.5%, 5.0%,
8.3%, and 12% emulsifiable concentrates and as a 0.8% ultra-low volume concentrate.
Laboratory Methods:
Analytic Laboratory Methods:
Product analysis of pyrethroids is by high performance liquid chromatography.
Residues may be determined by gas liquid chromatography with electron capture
detection.
Special References:
Special Reports:
Miyamoto J; Environ Health Perspect 14: 15-28 (1976). Degradation, metabolism,
and toxicity of synthetic pyrethroids.
Miyamoto J, et al; Pure Appl Chem 53: 1967-2022 (1981). The chemistry, metabolism,
and residue analysis of synthetic pyrethroids.
Hutson DH; Progress in Drug Metabolism 3: 215-252 (1979). The metabolic fate
of synthetic pyrethroid insecticides in mammals.
Casida JE et al; Ann Rev Pharmacol Toxicol 23: 413-38 (1983). The mechanisms
of selective action of pyrethroid insecticide are discussed.
Papadopoulou-Mourkidou E; Residue Rev 89: 179-208 (1983). A review with many references on analysis of allethrin & other pyrethroid insecticides.
Synonyms and Identifiers:
Synonyms:
3-(2-Chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylic
acid cyano(3-phenoxyphenyl)methyl ester.
**PEER REVIEWED**
[1alpha,3alpha(z)]-(+-)-Cyano-(3-phenoxyphenyl)methyl 3-(2-chloro-3,3,3- trifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate.
**PEER REVIEWED**
Cyhalothrine (French spelling)
**PEER REVIEWED**
Pesticide Code: 128867
**PEER REVIEWED**
Grenade
**PEER REVIEWED**
ICI 146 814
**PEER REVIEWED**
PP 563
**PEER REVIEWED**
(RS)-Alpha-cyano-3-phenoxybenzyl(z)-(1RS)-cis-3-(2-chloro-3,3,3- trifluoropropenyl)-2,2-dimethylcyclopropanecarboxylate
**PEER REVIEWED**
(RS)-Alpha-cyano-3-phenoxybenzyl (Z)-(1RS,3RS)-(2-chloro-3,3,3- trifluoropropenyl)-2,2-dimethylcyclopropanecarboxylate
**PEER REVIEWED**
Associated Chemicals:
Lambda-cyhalothrin;91465-08-6
Formulations/Preparations:
USEPA/OPP Pesticide Code 128867; Trade Names: ICI 146,814, Grenade, R114563,
PP 563.
Emulsifiable concentrate; wettable powder
Tech. grade cyhalothrin has purity greater than/equal to 90%, of which purity
greater than/equal to 95% is cis-isomers.
Commercial product exists as a mixture consisting of 95% cis-isomers
Technical grade cyhalothrin contains more than 90% of the pesticide and is
formulated in 5%, 10%, and 20% emulsifiable concentrates. Technical grade lambda-cyhalothrin
also contains more than 90% active ingredient. It is formulated as 2.5%, 5.0%,
8.3%, and 12% emulsifiable concentrates and as a 0.8% ultra-low volume concentrate.
Administrative Information:
Hazardous Substances Databank Number: 6791
Last Revision Date: 20011010
Last Review Date: Reviewed by SRP on 5/10/2001
Update History:
Complete Update on 10/10/2001, 51 fields added/edited/deleted.
Field Update on 08/08/2001, 1 field added/edited/deleted.
Field Update on 05/16/2001, 1 field added/edited/deleted.
Complete Update on 09/12/2000, 1 field added/edited/deleted.
Complete Update on 06/12/2000, 1 field added/edited/deleted.
Complete Update on 02/08/2000, 1 field added/edited/deleted.
Complete Update on 02/02/2000, 1 field added/edited/deleted.
Complete Update on 09/21/1999, 1 field added/edited/deleted.
Complete Update on 08/27/1999, 1 field added/edited/deleted.
Complete Update on 06/08/1999, 6 fields added/edited/deleted.
Field Update on 06/03/1998, 1 field added/edited/deleted.
Field Update on 11/01/1997, 1 field added/edited/deleted.
Field Update on 05/09/1997, 1 field added/edited/deleted.
Complete Update on 03/17/1997, 1 field added/edited/deleted.
Complete Update on 10/20/1996, 1 field added/edited/deleted.
Complete Update on 05/14/1996, 1 field added/edited/deleted.
Complete Update on 03/25/1996, 23 fields added/edited/deleted.
Field Update on 02/01/1996, 1 field added/edited/deleted.
Field Update on 08/21/1995, 1 field added/edited/deleted.
Complete Update on 03/01/1994, 54 fields added/edited/deleted.