It must be noted that the issue of a Data Sheet for a particular pesticide does not imply endorsement of the pesticide by WHO or FAO for any particular use, or exclude its use for other purposes not stated. While the information provided is believed to be accurate according to data available at the time when the sheet was compiled, neither WHO nor FAO are responsible for any errors or omissions, or any consequences therefrom.

The issue of this document does not constitute formal publication. It should not be reviewed, abstracted or quoted without the agreement of the Food and Agriculture Organization of the United Nations or of the World Health Organization.

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fenvalerate (BSI, E-ISO, F-ISO)

Fenvalerate is a mixture of four optical isomers which have different insecticidal activities. The 2-S alpha-S (or SS) configuration is the most insecticidally active isomer. Fenvalerate consists of about 23% of this isomer.

Synonyms and trade names: Belmark^R; Ectrin^R; Extrin; Fenkil; Fenvalethrin; Moscade^R; OMS-200; Pydrin^R; Pyrid; S-5602; Sanmarton^R; SD-43775; Sumibac^R; Sumicidin^R; Sumi-five^R; Sumifleece^R; Sumifly^R; Sumipower^R; Sumitick^R; Tirade^R; WL-43775.

Fenvalerate is a pyrethroid insecticide of moderate mammalian toxicity. In laboratory animals central nervous system toxicity is observed following acute or short-term exposure.

The stability of fenvalerate in sunlight allows its application against a wide range of pests. Residue levels are minimized by low application rates and poor translocation characteristics in plants and in soil. Fenvalerate is highly toxic to fish and bees.

The technical grade is a yellow-brown viscous liquid which may be partly crystallized at room temperature, and has a specific odour. Density at 25 ºC is 1.175 g/cm³. Not corrosive to metals.

Stable to moderate heat and sunlight. Rapidly hydrolysed above pH 8 but fenvalerate is relatively stable in acid media. Fenvalerate is not stable in alcohols.

0.037 mPa at 25 ºC.

Emulsifiable concentrates, flowable, ULV, wettable powders, slow release formulations, insecticidal fogs, granules and dusts.

A good contact and stomach insecticide for a wide range of pests including those resistant to organochlorine, organophosphorus and carbamate insecticides. Species controlled include flies, fleas, bollworms, leaf eaters, caterpillars, scale and other sucking insects.

Used to control insects on an extensive variety of leaves and fruits in food, feed and cotton production; and for the control of flies and ticks in barns and stables. Fenvalerate has no plant systemic activity but is active for a relatively long period. Re-application intervals should be based on levels of pest control attained rather than a rigid time interval. May be applied to walls or used as a slow release ear-tag formulation to control insects associated with animal husbandry.

Failure to observe specified application rate may produce phytotoxicity. Very toxic to fish and bees.

May be effective in the control of insects in public health programmes. No published information available on specific formulations, see Section 1.4 for general formulation and usage data.

No recommended usage reported.

Fenvalerate may be absorbed from the gastrointestinal tract, from the skin and following inhalation exposure. No quantitative data are available on the extent of absorption form the lung or across the skin.

Based on fenvalerate similarities with deltamethrin, toxicity is probably due to effects on both peripheral and central nervous system caused by interference with sodium ion permeability in stimulated nerve membranes. The toxic signs in laboratory animals include restlessness, tremors, piloerection, choreo-athetosis and salivation (CS-syndrome). Fenvalerate is classififed as type II pyrethroid.

In rats, fenvalerate undergoes extensive oxidative and hydrolytic metabolism to give hydoxylated phenoxy-esters; 3-phenoxybenzoic acid and 2-(4-chlorophenyl)-3-methylbutanoic acid and their hydroxylated derivatives and conjugates; thiocyanate and CO₂.

Following an oral dose of 8.4 mg/kg b.w. to male rats, excretion was approximately equally divided between the urine and the faeces. The 4'-hydroxy fenvalerate metabolite was excreted in the faeces only, but for the other major metabolites there were only quantitative differences between the two routes of excretion. At this dose very little fenvalerate was excreted unchanged and excretion of CO₂ accounted for <10% of the dose. Excretion was essentially rapid although small amounts of thiocyanate residues were more persistent in the skin and hair. Similar metabolites were excreted by mice, although the relative proportions of each metabolite showed a species difference. A taurine conjugate of 3-phenoxybenzoic acid was found in mouse but not in rat excreta. In both species the metabolic profile did not differ between the sexes, nor with magnitude of dose. In the rat the isomer composition did not affect the excretion pattern. Administration of 500 mg/kg diet to rats for two weeks prior to receipt of the radio-labelled dose had no effect on the metabolite profile, but caused a slightly increased excretion rate and lower thiocyanate residues in the skin and hair.

Lactating Holstein cows were fed fenvalerate at 5 and 15 mg/kg diet for 4 days and were then given ordinary diet for 6 days. Total excretion of the compound in the milk amounted to 0.44 and 0.64% of the total dose for the 5 and 15 mg/kg levels, respectively, when 25% of the dose was eliminated in the faeces. Single oral dose of 10 mg/kg b.w. to chickens resulted in maximum egg yolk concentration of 0.3 mg/kg and egg white of 0.24 mg/kg after 4 to 5 days.

Immediately after receipt of a toxic dose of fenvalerate, rats showed an abnormal gait affecting the hind limbs. Histopathologic changes of the nerves were seen in these rats (Section 2.1.7). Initial symptoms of poisoning also included restlessness, tremors, choreo-athetosis, piloerection, profuse salivation and occasional diarrhoea. Surviving animals were asymptomatic 3-4 days later.

Fenvalerate did not induce consistent cardiovascular effects when administered in acute toxic doses to dogs. Respiratory stimulation was noted at high dosage levels, and was not reduced by anaesthesia.

Severe skin and eye irritation was observed in rabbits following exposure to emulsifiable concentrate and ULV formulated products. Dermal irritation persisted for seven days following 24 hour contact. Severe conjunctivitis, corneal opacity and iritis occurred within 30 minutes of instillation of 0.2 ml of the formulation into the conjunctival sac.

Skin sensitization by pure fenvalerate (95%) has been tested on guinea-pigs. No sensitization was detected.

Oral: Rats receiving oral doses of 400 mg/kg b.w./day for 7 days and hamsters receiving 40 mg/kg b.w./day for five days, showed changes in motor function which were accompanied by biochemical and histopathological changes in the nerves.

Dermal: Dermal application of 400 mg/kg b.w./day for six hours, 14 times within 22 days, caused a severe weight loss in rabbits. Clinical signs of poisoning, mortalities and gross dermal effects were also observed. Minor, local dermatologic effects were observed at 100 mg/kg b.w. day.

Short-term: Administration of  500 mg/kg diet to rats for 90 days caused an increase in the relative liver and kidney weights. Decreased growth and food consumption were seen at doses  1000 mg/kg diet, accompanied by an increase in blood urea nitrogen. Deaths were recorded at 2000 mg/kg diet. No other adverse effects on biochemical, haematological or histopathogical parameters were observed. Dietary administration of fenvalerate to dogs for 90 days caused no observable effect on clinical chemistry or histopathology at concentrations equivalent to 12.5 mg/kg b.w./day.

Granulomatous changes were observed in the liver, spleen and mesenteric lymph node of ddY mice receiving 1000 or 3000 mg/kg diet for six weeks. The lesions progressively diminished after cessation of exposure, but were still apparent after a 12-month recovery period. The response has been defined as a foreign-body inflammatory reaction to cholesteryl esters of fenvalerate metabolites.

Long-term: A transient ataxia, abnormal gait and muscular incoordination of the hind limbs were observed in 6 of 50 male Sprague Dawley rats receiving 1000 mg/kg diet, 3-4 weeks after initiation of a two year feeding study. Decreased body weight and increased relative but not absolute organ weights were observed in both sexes at this dose. No other adverse effects on food consumption, biochemical or histopathological parameters are cited.

In B6C3F1 mice an adverse effect on body weight was observed following lifetime exposure to  250 mg/kg diet; at 1250 mg/kg diet longevity was decreased. These mice and ddY mice receiving  250 and  100 mg/kg diet respectively, for 12 months or longer showed evidence of an inflammatory response in the liver, lymph nodes or spleen. A similar response was observed in Wistar rats receiving 500 mg/kg diet but the adrenals also showed an inflammatory response. The response was typified by giant cell infiltration and/or multifocal microgranulomata. The reaction has been defined as a foreign-body type of response, elicited by deposition of crystals of cholesteryl 2-(4-chlorophenyl)-3-methylbutanoic ester in the tissues. In a differential metabolism study in rats and mice the concentration of a lipophilic metabolite (cholesteryl [2R]-2-(4-chlorophenyl)isovlaerate) was found to be highest in adrenals, liver and lymph nodes. A similar inflammatory response has also been observed in dogs, fed a diet containing up to 1000 mg fenvalerate/kg diet for a period of 6 months.

No evidence of carcinogenicity was observed in ddY and B6C3F1 mice fed on a diet containing up to 3000 mg/kg/diet and 1250 mg/kg/diet, respectively. An equivocal increase in spindle-cell sarcoma of the dermis and subcutis was observed in Sprague Dawley rats receiving 1000 mg/kg diet, but when reviewed and re-classified according to the cell-type involved the incidence was not significant.

No teratogenic effect was observed in mice and rabbits following oral administration of 50 mg/kg b.w./day on gestation days 6-15 and 6-18, respectively.

In a standard three-generation reproduction study in rats, a reduced body weight in the F2b generation at 250 mg/kg diet was the only adverse effect observed. The weight loss was not supported by histopathological findings.

Fenvalerate was not mutagenic in several strains of Salmonella typhimurium or Bacillus subtilis, nor in V79 Chinese Hamster cells, with or without metabolic activation.

No mutagenic effect was observed in a host-mediated assay with S. typhimurium following oral administration of 125 mg fenvalerate/kg b.w. to mice, nor in a host mediated assay with Saccharomyces cerevisiae following oral administration of 50 mg fenvalerate /kg b.w. to mice.

No evidence of chromosomal damage was seen in hamster bone marrow following receipt of two oral doses of 25 mg/kg b.w./day.

Equivocal evidence suggested that fenvalerate did not cause dominant lethal mutations in mice at oral doses of 100 mg/kg b.w./day.

Transient hypersensitivity, behavioural changes, hind limb ataxia and deficits in motor performance have been observed in rats, mice and hamsters following acute or chronic exposure to fenvalerate. Dose dependant histopathological changes include axonal breaks, swelling and degeneration of the myelin and increases in lysosomal enzyme activity in the posterior fibular and sciatic nerves.

No adverse clinical or histopathological findings were observed following a single oral administration of 200 mg/kg b.w. to rats. Lesions of the sciatic nerve were observed in rats following 10 days administration of 3000 mg/kg diet and were still apparent three weeks after cessation of exposure, but not after a six week recovery period. No adverse histopathological effects have been reported in the sciatic nerves of animals following chronic and subchronic exposure, confirming the recovery from the transient episodes of ataxia displayed during early stages of these studies.

The severity of the toxic symptoms elicited by acute fenvalerate poisoning in rats could be reduced by phenobarbital, diphenylhydantoin or pentobarbital administration.

Fenvalerate may be absorbed from the gastrointestinal tract, from the skin and following inhalation exposure.

No published information available.

Cutaneous sensations of stinging and burning have been reported by workers using fenvalerate formulations. The sensations were generally confined to exposed areas of the body such as the face and upper extremities. Symptoms usually occurred several hours after exposure, and persisted for less than 24 hours, while systemic symptoms could appear as late as 48 hours after exposure. No inflammatory reaction was observed. Neither tolerance nor potentiation of the reaction was reported with continued exposure. During 1983-1988 in China, 63 cases of occupational acute fenvalerate poisoning were reported.

No published information available.

Tingling, numbness and itching sensations were reported following application of fenvalerate solutions to the ear lobes of volunteers. No volunteer reported an immediate effect; peak effect was generally 3-6 hours after application, persisting for less than 24 hours. Erythema and oedema did not accompany the sensation. The non-steroidal anti-inflammatory drug indomethacin did not alleviate the paraesthesia. The effect appears to be due to direct stimulation of cutaneous nerve endings.

Accidental acute intoxications with 20% fenvalerate emulsion (10-500 ml) are reported in the literature. Most of the cases were related to acute fenvalerate poisoning following ingestion, although there are single cases reported on accidental dermal intoxication in children by spilling fenvalerate on head, face and eyes. After symptomatic and supportive treatment, patients usually recover after 1 to 6 days. However, lethal outcome due to convulsions and pulmonary oedema were reported as well.

Highly toxic to fish.

Highly toxic to honey bees. Contact LD₅₀ 0.23 μg/bee.

[For definition of categories see the "Introduction to data sheets".]

Formulations in categories 3 and 4: Should be transported in clearly labelled, rigid and leakproof containers, away from food and drink. Storage should be under lock and key and secure from access by children and other unauthorized persons.

Formulations in categories 3 and 4: Protective clothing (see section 4.1.3) should be used. Adequate washing facilities should be available at all times and should be close to the site of handling. Eating, drinking and smoking should be prohibited during handling and after handling before washing of hands and face.

Containers must be decontaminated (for method see section 4.3). Decontaminated containers should not be used for storage or transportation of any food or drink. Containers that are not contaminated should be burned or crushed and buried below topsoil. Care must be taken to avoid subsequent contamination of water sources.

All Formulations: Training of workers in techniques to avoid contact is essential, and account should be taken of the workers' ability to comprehend and follow instructions.

All formulations: Pilots and loaders should have special training in application methods and recognition of early warning symptoms of poisoning. Full protective clothing must be worn at all times and should include overalls, impermeable boots and gloves, a face mask and goggles. Flagmen should additionally wear an impermeable brimmed hat and be located well away from the dropping zone.

Formulations in categories 3 and 4 - minimum cautionary statement:

Fenvalerate is a pyrethroid insecticide. It is poisonous if swallowed causing neurotoxic effects. It may also be absorbed from the skin or by inhalation of sprays and mists. Fenvalerate is an irritant and contact with skin, the mouth and eyes should be avoided. Wash thoroughly after using. Keep out of reach of children and away from food and feedstuffs.

Maximum residue limits have been recommended by the Joint FAO/WHO Meeting on Pesticide Residues. An acceptable daily intake (ADI) of 0-0.02 mg/kg b.w. was established for fenvalerate by JMPR in 1986.

Fenvalerate is a pyrethroid insecticide of moderate toxicity. It may be absorbed from the gastrointestinal tract, from the lungs and through the skin. Concentrated solutions of fenvalerate may cause skin and eye irritation. Unpleasant tingling and itching of the skin may follow dermal contact with diluted formulations.

No published information available. Closed systems and forced ventilation may be required to reduce as much as possible the exposure of workers to fenvalerate.

When opening the container and when mixing, protective impermeable boots, clean overalls, gloves and a suitable respirator should be worn. Mixing, if not mechanical, should always be carried out with a paddle of appropriate length. When spraying tall crops or during aerial application, a face mask should be worn, as well as an impermeable hood, clothing, boots, and gloves. The applicator should avoid working in spray mist and avoid contact with the mouth. Particular care is needed when equipment is being washed after use. All protective clothing should be washed separately from other laundry immediately after use, including the insides of gloves. Splashes must be washed immediately from the skin, or eyes with large quantities of water. Before eating, drinking, or smoking, hands and other exposed skin should be washed.

Persons exposed to fenvalerate and associated with its application should wear protective clothing and observe the precautions described above in Section 4.1.3 under "Mixers and applicators". Flagmen should obey the additional protective clothing requirements detailed in Section 3.6.

With good agricultural practice, subject to 4.2 and 4.3 below, other persons should not be exposed to hazardous amounts of fenvalerate. Recommended time intervals between application and harvest have been stipulated by the FAO/WHO Joint Meeting on Pesticide Residues and range from 3-28 days.

Unprotected persons should be kept out of treated areas for 24 hours to reduce the risk of unpleasant numbness and tingling of the skin. Areas treated with fog formulations must be thoroughly ventilated before re-entry is allowed.

Residues in containers should be emptied in a diluted form into a deep pit, taking care to avoid contamination of water sources. The empty container may be decontaminated by rinsing three times with detergent and water and scrubbing the sides. An additional rinse should be carried out with 5% sodium hydroxide solution which should remain in the container overnight. Impermeable gauntlets should be worn during this work, and a soakage pit provided for the rinsings. Decontaminated containers must not be used for transportation or storage of food or drink.

Spillage of liquid formulations should be contained by absorbent material. This material, or spillage of solid formulations should be collected and burned or buried in a deep pit, taking care to avoid contamination of water sources. Fenvalerate residues should be removed from the spillage site by washing with 5% sodium hydroxide solution and then rinsing with large quantities of water.

In patients with occupational intoxication, the initial symptoms were burning or itching sensations of the face or dizziness which usually developed at 4-6 hours after exposure. In the case of ingestive poisoning, the symptoms were mainly digestive, such as epigastric pain, nausea and vomiting which developed within 10 minutes to 1 hour after ingestion. Spilling fenvalerate on the head, face and eyes immediately induced pain, lacrimation, photophobia, congestion and oedema of conjunctiva and eyelids. Severe exposure may cause an initial hypotension and slow heart rate, followed by hypertension, increased heart rate and convulsive muscle contractions.

The person should stop work immediately, remove contaminated clothing and thoroughly wash the affected skin with soap and water. For eye contamination wash with copious amounts of water. Do not induce vomiting following ingestion of emulsifiable concentrate formulations and do not induce vomiting unless the person is fully conscious. Otherwise vomiting may be induced following ingestion of fenvalerate. In the event of collapse apply artificial respiration.

Fenvalerate is a pyrethroid insecticide of moderate toxicity to mammals. Absorption may follow ingestion, inhalation or dermal exposure to fenvalerate and its formulations. Fenvalerate is a neurotoxin, acting through an impairment on Na-K exchange channels in nervous membranes.

Little information is available on the acute toxic effects of fenvalerate in humans. Based on animal studies of this and related α-cyano pyrethroids, high doses cause salivation, coarse tremors or writhing. Ataxia, respiratory and cardiovascular dysfunction may also occur. Tingling, itching and numbness have been reported following dermal exposure to fenvalerate. Typically these cutaneous sensations appear a few hours after exposure, and persist for less than 24 hours, and are considered as local effects.

Fenvalerate is rapidly metabolized to numerous products and quantization of exposure by determining residues in body fluids is probably too complex to be a useful monitoring system.

There are no specific antidotes and treatment must be symptomatic. Following ingestion of a large amount of fenvalerate, gastric lavage should be performed. Precautions should be taken to avoid pulmonary complications from solvents present in some formulations. Activated charcoal should be given, by stomach tube if necessary, to limit absorption of remaining fenvalerate. Ingestion of small amounts of fenvalerate should be treated by administering a large dose of activated charcoal. In case of convulstions, treatment with diazepam is recommended.

Contamination of the skin or eyes should be treated by washing with copious amounts of water. Soothing creams may alleviate skin irritation but anti-inflammatory agents may not relieve the dermal tingling and burning which may be felt several hours after exposure.

None.

Ambrus A, Lantos J, Visi E, Csatlos I, Sarvari L (1981), J Assoc Off Anal Chem 64(3): 733-742.

Chapman RA and Harris CR (1978), J Chromatog 166:513-518.

Reichel WI, Kolbe E, Stafford CJ (1981), J Assoc Off Anal Chem 64(5):1196-1200.

IARC (1991), Fenvalerate. In: Occupational Exposures in Insecticide Application, and some Pesticides. Lyon, International Agency for Research on Cancer, pp.309-328, IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, Vol. 53.

FAO (1985), Pesticide Residues in Food - 1984 Evaluations. FAO Plant Production and Protection Paper 67, Rome, Food and Agriculture Organization of the United Nations.

The Pesticide Manual, A World Compendium (10th edition 1994), Tomlin, C., ed., British Crop Protection Council, 20 Bridport Road, Thornton Heath, CR4 7QG, U.K.

    See Also:
       Toxicological Abbreviations
       Fenvalerate (EHC 95, 1990)
       Fenvalerate (HSG 34, 1989)
       Fenvalerate (ICSC)
       Fenvalerate (Pesticide residues in food: 1979 evaluations)
       Fenvalerate (Pesticide residues in food: 1981 evaluations)
       Fenvalerate (Pesticide residues in food: 1984 evaluations)
       Fenvalerate (Pesticide residues in food: 1984 evaluations)
       Fenvalerate (IARC Summary & Evaluation, Volume 53, 1991)