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         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    Ce document ne constitue pas une
    not constitute formal              publication. Il ne doit faire
    publication. It should not be      l'objet d'aucun compte rendu ou
    reviewed, abstracted or quoted     résumé ni d'aucune citation sans
    without the agreement of the       l'autorisation de l'Organisation
    Food  and Agriculture              des Nations Unies pour
    Organization of the United         l'Alimentation et l'Agriculture
    Nations or of the World Health     ou de l'Organisation Mondiale de
    Organization.                      la Santé.


                             Primary use:      Insecticide

                             Secondary use:    Acaricide

                             Chemical group:   Organophosphorus compound

                             Date issued:


    1.1  COMMON NAME: Fenitrothion (ISO)

    Identity: O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate


    Synonyms: OMS-43, sumithion, folithion, accothion, novathion,

    Local synonyms:

    1.2  SYNOPSIS

    An organophosphorus insecticide and selective acaricide of moderate
    mammalian toxicity.


    1.3.1  Physical characteristics

    Brownish yellow liquid of b.p. 145°C at 0.4 mm Hg (0.53 mbar) with

    1.3.2  Solubility

    Practically insoluble in water but soluble in most organic solvents;
    low solubility in aliphatic hydrocarbons.

    1.3.3  Stability

    It is hydrolysed by alkali and its half-life in 0.01 N NaOH at 30°C
    is 272 minutes. It readily isomerizes on distillation. Completely
    stable for two years at 20-25°C.

    1.3.4  Vapour pressure

    (volatility) low, 6 x 10-6 mm Hg at 20°C, or 8 x 10-6 mbar at


    1.4.1  Common formulations

    Emulsifiable concentrates 50%; dusts 2, 3 and 5%; wettable powders
    40% and 50%; granules 3% and 5%, baits, ULV.

    1.4.2  Susceptible pests

    Aphids, weevils, sandfly, raspberry beetle, tortrix, midges, moths,
    thrips, ermine moth, leatherjackets, leaf hoppers, rice borers, and

    1.4.3  Use pattern

    Used on cotton and rice at up to 2 kg/ha; used on vegetables at up
    to 1.25 kg/ha; used on cereals at up to 1.0 kg/ha; used in forestry
    and on cocoa at up to 0.5 kg/ha; coffee, spray concentration 0.1%;
    top fruit, spray concentration 0.1%; ornamentals, spray
    concentration 0.1%; sugar cane, spray concentration 0.075; tea,
    spray concentration 0.05%.

    1.4.4  Unintended effects

    Should not be used on flowering crops. Phytotoxicity is possible on
    brassicae and orchard fruit - should not be applied directly to
    grains. Livestock may be affected if given access to treated areas
    within one week of application.


    Successfully tested on residual insecticide for control of malaria
    vectors, as a 5% suspension of water dispersible powder. This is
    applied on the surfaces indoors at 2 g/m2 at a three-monthly
    interval. Also used as ULV application from ground or air, technical
    insecticide being applied at the rate of 250-500 ml/ha for the
    control of vital epidemics transmitted by Aedes aegypti or Culex
    sp. It has also been used as a mosquito larvicide at dosage rates
    varying from 224 to 336 g/ha.


    No known use.



    2.1.1  Absorption route

    Absorbed from the gastrointestinal tract as well as by the intact
    skin and by inhalation.

    2.1.2  Mode of action

    An organophosphorus cholinesterase inhibitor.

    2.1.3  Excretion

    Converted to the oxygen analogue. Metabolites include
    3-methyl-4-nitrophenol and 3-carboxy-4-nitrophenol. Up to nine
    metabolites have been isolated. Excretion is mainly in the urine
    90-95% and up to 10% in the faeces.

    2.1.4  Toxicity, single dose

    Oral LD50 rat (M) 504 mg/kg

    Dermal LD50 rat (M & F) 3500 mg/kg

    Most susceptible species, cat (M) oral LD50 142 mg/kg

    2.1.5  Toxicity, repeated doses

    Oral: No fatalities occurred among male rats dosed for 28 days at
    13 mg/kg/day, however, erythrocyte cholinesterase activity was
    reduced and recovery took 30 days after cessation of dosing. Twenty
    male rats dosed orally six days a week for two months at 10 and
    11 mg/kg, showed some deterioration of general condition and weight
    loss during the first weeks. However, haematology and urinalysis
    during the experiment and histological examination at its
    termination, did not reveal any abnormalities.

    Dogs of both sexes were dosed orally by capsule at 2.9 or 40 mg/kg
    for 98 days. Body weights, blood biochemistry, cholinesterase levels
    and haemograms were checked at intervals. No effect was found at
    2 mg/kg. At 9 mg/kg there was a slight reduction of whole blood,
    plasma and erythrocyte cholinesterase activities, after 60 days, and
    at 40 mg/kg a moderate reduction after 29 days. At 40 mg/kg, marked
    cholinergic symptoms were observed.

    Inhalation: Groups of six male and female rats, Sprague Dawley
    strain, were exposed to fenitrothion mist during two hours per day
    for five consecutive days. The aerial concentration of fenitrothion

    in the chamber was approximately 62, 15 and 8 mg/m3. Plasma,
    erythrocyte and brain cholinesterase activities of the rats exposed
    to 7 mg/m3 of fenitrothion for five days showed no reduction as
    compared with the control, while at the dose of 15 mg/m3 of
    fenitrothion plasma cholinesterase activity was reduced
    approximately by 30-50%. At 62 mg/m3 erythrocyte cholinesterases
    were inhibited by 50% or more. Brain cholinesterase activity was not
    affected at the lower dosages and only by exposure to 62 mg/m3 of
    fenitrothion was it reduced to about 50% of the control.

    In another trial, groups of 16 male and 16 female rats and 15 each
    of male and female mice, were exposed to 1 and 0.2% fenitrothion
    mist for two hours, six days per week for four weeks; plasma and
    erythrocyte cholinesterase recovered within seven days after
    termination of the exposure to 0.2% fenitrothion, and at the higher
    dosage (1%) both cholinesterases were still 10-20% below the control
    values after 14 days. None of the rats died during four weeks of
    exposure, and there were no adverse effects on weight gain,
    haematology, clinical biochemistry, organ weight and histopathology.
    Similar results were obtained with mice.

    Cumulation of compound: Does not accumulate in body tissues to any
    significant extent.

    Cumulation of effect: Repeated exposure may produce cumulative
    inhibitory effect on cholinesterase. Acute effects are prolonged and
    recovery of erythrocyte cholinesterase activity after severe
    inhibition may take up to 30 days.

    2.1.6 Dietary studies

    Short-term: Groups of male rats (16 or 17 in number), were fed 0,
    32, 63, 125, 250, and 500 ppm of fenitrothion in the diet for 90
    days. All the animals fed 500 ppm showed clinical symptoms of
    anticholinesterase poisoning and there were minimal symptoms in four
    animals in the 250 ppm group. In the 500 ppm group, the average
    weight of testes and brain were increased in comparison with those
    of the control group. Cholinesterase activity of plasma,
    erythrocyte, brain cortex, liver and kidneys showed a dose-dependent
    reduction, the lowest being in the brain. The cholinesterase
    activity in the 32 and 63 ppm groups generally recovered after 60
    days of dosing to a level within the normal limits, the best
    recovery being in the plasma, kidney and brain, less in the
    erythrocyte and the liver.

    Long-term: Fenitrothion was fed to groups of male and female
    beagle dogs at concentrations ranging from 5 to 200 ppm for periods
    of one to two years. In the first trial, groups of dogs (six males
    and six females per group) were fed fenitrothion for two years at
    doses of 30, 100 or 200 ppm in the diet. No measurable deviations
    from the control were found in the treated groups with respect to

    growth, food consumption, behavioural reactions, mortality
    haematology and clinical blood chemistry values, urinary analysis,
    organ weights and their ratio to body weight and gross and
    microscopic pathological examinations. At 30 ppm, erythrocyte
    cholinesterase activity was unaltered but plasma cholinesterase was
    reduced throughout the two-year experiment. Brain cholinesterase
    activity was not affected at the highest dose level.

    Additional sub-acute feeding study was carried out to check blood
    cholinesterase activity at the doses of 5 and 10 ppm for one year.
    Five out of eight beagles exposed to 5 ppm of fenitrothion showed
    slight reduction of plasma enzyme activity for the first three
    months, but the activity recovered thereafter. Brain cholinesterase
    was normal. The "no effect" level of fenitrothion for cholinesterase
    activity was determined to be 5 ppm. Several studies on long-term
    oral toxicity of fenitrothion, including carcinogenicity study have
    been carried out in rats. It was found that fenitrothion fed at
    concentrations from 2.5 to 150 ppm for periods ranging from six
    months to two years produced no measurable deviation from the normal
    with respect to the parameters investigated except cholinesterase
    activity. Fenitrothion fed to rats at a concentration of 5 ppm was
    determined as the "no effect" level with regard to cholinesterase

    2.1.7  Supplementary studies of toxicity

    Carcinogenicity: See 2.1.6, dietary studies, long-term.

    Reproduction study: Fenitrothion was administered in the diet to
    albino rats at dosage levels of 10, 30 and 150 ppm through weaning
    of the first (F1A litters) filial generation and 10, 30 and
    100 ppm thereafter. Body weight reduction occurred due to the
    feeding of 150 ppm fenitrothion to the P1 generation animals and
    100 ppm fenitrothion to the P2 generation animals. Lactation index
    was significantly depressed for all the filial generations at the
    highest dietary levels of fenitrothion. At these levels, weaning
    body weights of both sexes of the F1A, males of the F1B, and
    both sexes of the F2A generations were significantly lower than
    the respective control values. The organs of representative
    weanlings sacrificed from control and test groups showed no gross
    compound-related changes at any of the test levels. No microscopic
    evidence of compound-related histomorphologic alterations were
    present in sections of thyroid, liver, kidney, stomach and small
    intestine taken from male and female F3B weanlings which received
    the highest level (100 ppm) of fenitrothion.

    Teratogenicity: Technical fenitrothion was administered to
    pregnant albino rabbits at daily rates of 0.3 mg/kg and 1.0 mg/kg of
    body weight during early gestation. No adverse effects on body
    weight gain were noted which could be attributed to fenitrothion. No

    deaths or unusual reactions were noted among females. Foetal
    mortality was not affected by the treatment with fenitrothion, nor
    were any external and skeletal abnormalities observed among the

    Delayed neurotoxicity: Tests in hens at 250, 400 and 500 mg/kg
    have not revealed any paralysis or associated nerve damage. In rats
    fed 10 mg/kg/day for six months, fine structure of neuromuscular
    junctions was unchanged.

    2.1.8  Modification of toxicity

    In potentiation studies among several organophosphorus compounds
    tested in combination with fenitrothion, only phosphamidon has shown
    positive effects in both male and female rats, as evidenced by
    increased mortality.


    2.2.1  Absorption

    Absorbed from the gastrointestinal tract as well as by inhalation
    and by the intact skin.

    2.2.2  Dangerous doses

    Single: Not known.

    Repeated: Not known.

    2.2.3  Observations of occupationally exposed workers

    Fenitrothion is applied as a residual indoor spray for adult
    mosquito control. When supervision, including cholinesterase
    monitoring, has been adequate, there have been no cases of poisoning
    during residual indoor spraying. Only in a few instances has it been
    necessary to remove individuals from spraying due to symptomless
    reduction of whole blood cholinesterase activity, usually observed
    towards the end of six to eight weeks spraying cycles. No cases of
    poisoning occurred.

    2.2.4  Observations on exposure of the general population

    In a malaria control trial in northern Nigeria involving 10 000 and
    16 500 people, whole blood cholinesterase levels were unaffected in
    299 villagers representative of this population, tested 5-30 days
    after their houses had been sprayed. This represents a higher
    exposure than encountered by its proper agricultural use.

    Fenitrothion has been used in agriculture for a number of years
    without any cases of poisoning being reported.

    2.2.5  Observations of volunteers

    Single dose:  Twenty-four volunteers were given a single oral dose
    of from 2.5 to 20 mg of fenitrothion. In one case there was some
    reduction of plasma cholinesterase activity, six and 24 hours after
    receiving the largest dose. The excretion of the metabolite
    3-methyl-4-nitrophenol in urine was maximal at 12 hours and almost
    complete at 24 hours.

    Repeated: Five individuals were given four daily doses of 2.5 and
    5 mg fenitrothion. Metabolites appeared in the urine at 0-12 hours
    after administration. After the third and fourth doses there was a
    tendency towards a rise in erythrocyte cholinesterase levels. No
    cholinesterase inhibition was seen in the plasma.

    2.2.6  Reported mishaps

    Accidental poisoning has occurred but no large-scale mishaps have
    been reported.


    2.3.1  Fish

    Toxic (4.4 ppm/h for carp; 1.0 ppm/h for trout).

    2.3.2  Birds

    Moderately toxic (LD50 523 mg/kg for chickens; for wild birds:
    mallard duck 1190 mg/kg, pheasant 55.6 mg/kg).

    2.3.3  Other species

    Toxic to bees and livestock, game and wild animals.



    (for definition of categories, see introduction)

    All formulations 10% or above, Category 4

    Formulations below 10%) Category 5


    All formulations in Category, 4:  Should be transported or stored
    in clearly labelled, rigid and leakproof containers. No food or
    drink should be transported in the same compartment. Storage should
    be under lock and key and secure from access by unauthorized persons
    and children.

    Formulations in Category 5:  Should be transported in clearly
    labelled, leakproof containers, out of reach of children and away
    from food and drink.

    3.3  HANDLING

    All formulations in Category 4: Full protective clothing should be
    used by all those handling the compound. Adequate washing facilities
    should be available at all times during handling and should be close
    to the site of handling. Eating, drinking and smoking should be
    prohibited during handling and before washing after handling. Some
    liquid formulations contain flammable volatile solvents.

    Formulations in Category 5: No facilities other than those needed
    for handling of any chemical need be required.


    All formulations: Containers may be decontaminated (for method see
    para. 4.3). Decontaminated containers should not be used for food or
    drink. Containers that are not decontaminated should be burned or
    should be crushed and buried below topsoil. Care must be taken to
    avoid subsequent contamination of water sources.


    All formulations in Category 4: Pre-employment medical examination
    of workers desirable. Workers suffering from active hepatic or renal
    disease should be excluded from contact. Special account should be

    taken of the workers' mental ability to comprehend and follow
    instructions. Training of workers in techniques to avoid contact
    essential. Pre-employment and routine cholinesterase test for
    workers is desirable.

    Formulations in Category 5: Warning of workers to minimize contact


    All formulations: Pilots and loaders should have special training
    in application methods and recognition of early symptoms of
    poisoning. Use of flagmen not recommended. Flagmen if used should
    wear protective clothing and be located well away from the dropping

    3.7  LABELLING

    All formulations in Category 4: Fenitrothion is an
    organophosphorus compound that inhibits cholinesterase. It is
    poisonous if swallowed or inhaled. It may be absorbed through the
    skin. Avoid skin contact; wear hand protection, clean protective
    clothing, and, if in poorly ventilated area, a respirator when
    handling the material. Wash thoroughly with soap and water after
    using. Keep out of reach of children and well away from foodstuffs,
    animal feed and their containers. If poisoning occurs, call a
    physician. Atropine and pralidoxime are specific antidotes and
    artificial respiration may be needed.

    Formulations in Category 5: Fenitrothion is a toxic substance. It
    is poisonous if swallowed. It may be absorbed through the skin or
    inhaled as dust or mists. Avoid skin contact, wear protective gloves
    and clean protective clothing while using this material. Wash
    thoroughly with soap and water after using. Keep the material out of
    reach of children and well away from foodstuffs, animal feed and
    their containers.


    Maximum residue limits for fenitrothion have been recommended by the
    Joint FAO/WHO Meeting on Pesticide Residues.



    Fenitrothion is an organophosphorus insecticide of moderate
    toxicity. It can be absorbed by mouth, by inhalation of the dust and
    through the intact skin. Most formulations should be handled by
    trained personnel wearing protective clothing.

    4.1.1  Manufacture and formulation

    TLV: No information. Although volatility is low, vapour and dust
    should be controlled preferably by mechanical means. Protective
    equipment for the skin and respiratory protection is usually

    4.1.2  Mixers and applicators

    When opening the container and when mixing, care should be taken to
    avoid contact with the mouth and eyes. If necessary a facial visor
    and gloves should be worn. Mixing if not mechanical, should always
    be carried out with a paddle of appropriate length. 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 immediately after use,
    including the inside 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.

    4.1.3  Other associated workers (including flagmen in aerial

    Persons exposed to fenitrothion and associated with its application
    should observe the precautions described in 4.1.3 under "mixers and

    4.1.4  Other populations likely to be affected

    With good agricultural practice, subject to 4.2 below, other
    populations should not be exposed to hazardous amounts of


    Unprotected persons should be kept out of treated areas for at least
    one day.


    Residues in containers should be emptied in a diluted form into a
    deep pit taking care to avoid ground waters. The empty container may
    be decontaminated by rinsing two or three times with water and
    scrubbing the sides. In additional rinse should be carried out with
    5% sodium hydroxide solution which should remain in the container
    overnight. Impermeable gloves should be worn during this work and a
    soakage pit should be provided for the rinsings. Decontaminated
    containers should not be used for food and drink. Spillage of
    fenitrothion and its formulations should be removed by washing with
    5% sodium hydroxide solution and then rinsing with large quantities
    of water.


    4.4.1  Early symptoms of poisoning

    Early symptoms may include excessive sweating, headache, weakness,
    giddiness, nausea, and vomiting, stomach pains, joint and muscle
    pains, slurred speech, blurred vision and constricted pupils.

    4.4.2  Treatment before person is seen by a physician; if these
           symptoms appear following exposure

    The person should stop work immediately, remove contaminated
    clothing, wash the affected skin with soap and water, if available,
    and flush the area with large quantities of water. If swallowed,
    vomiting should be induced if the person is conscious. In the event
    of collapse, artificial respiration should be given, bearing in mind
    that if mouth-to-mouth resuscitation is used, vomit may contain
    toxic amounts of fenitrothion.



    5.1.1  General information

    An organophosphorus pesticide of moderate toxicity which is absorbed
    through the intact skin as well as by inhalation and from the
    gastrointestinal tract. It is converted in vivo to the oxygen
    analogue (fenitrothion) which is an active cholinesterase inhibitor.
    Prolonged and continuous exposure to low amounts may inhibit blood
    cholinesterase to hazard levels.

    5.1.2  Symptoms and signs

    Initial symptoms of poisoning may include excessive sweating,
    headache, weakness, giddiness, nausea, vomiting, stomach pains,
    muscle and joint pains, blurred vision, slurred speech, muscle
    twitching and hypersalivation. More advanced symptoms of poisoning
    may include coma, cyanosis, loss of sphincter control and loss of

    5.1.3  Laboratory

    The most important laboratory finding is reduction in activity of
    blood cholinesterases.

    5.1.4  Treatment

    If the pesticide has been ingested, unless the patient is vomiting,
    rapid gastric lavage should be performed using 5% sodium
    bicarbonate, if available. For skin contact the skin should be
    washed with soap and water. If the compound has entered the eyes,
    they should be washed with isotonic saline or water.

    Persons without signs of respiratory inefficiency but with manifest
    peripheral symptoms should be treated with 2-4 mg of atropine
    sulfate and 1000-2000 mg of pralidoxime chloride or 250 mg of
    toxogonin (adult dose) by slow intravenous injection. More atropine
    may be given as needed. Persons with severe intoxication with
    respiratory difficulties, convulsions and unconsciousness should
    immediately be given atropine and a reactivator; in such severe
    cases 4-6 mg of atropine sulfate should be given initially followed
    by repeated doses of 2 mg at 5-10 minute intervals. The patient's
    condition, including respiration, blood pressure, pulse frequency,
    salivation and convulsions should be carefully observed as a guide
    to further administration of atropine. If the patient is cyanotic,
    artificial respiration should be administered at the same time as
    atropine sulfate. The airways should be kept free and artificial
    respiration should be applied, if required, preferably by mechanical
    means. If necessary, intubation should be performed.

    Contraindications are morphine, barbiturates, phenothiazine,
    tranquillizers, and central stimulants of all kinds.

    5.1.5  Prognosis

    If the acute toxic effects are survived and these may be prolonged,
    and adequate artificial respiration has been given, the chances of
    complete recovery are good. However, in very severe cases,
    particularly if artificial respiration has been inadequate,
    prolonged hypoxia may give rise to permanent brain damage.

    5.1.6  References of previously reported cases

    No clear-cut poisoning cases. However, the following references may
    be helpful:

    Matsushima, S. (1972) Baioteku, 3(4), 258

    Tshikawa, T. (1972) Baioteku, 3(4), 263


          Test                    Normal level*    Action level*    Symptomatic level

    Plasma cholinesterase            100%             50%                Variable

    Erythrocyte cholinesterase       100%             70%              Usually 40%

    *Expressed as percentage of pre-exposure activity.


    5.3.1  Detection and assay of compound

    It is unlikely that unchanged fenitrothion will be detectable in
    human tissues after exposure. Determination of levels of blood
    cholinesterase and urinary 3-methyl-4-nitrophenol (see 5.3.2 below)
    should be used in cases of suspected poisoning.

    Residues may be determined by hydrolysis to 3-methyl-4-nitrophenol
    which is measured at 400 mu by difference in absorbency in acid and
    alkaline solution or by gas liquid chromatography; see Möllhoff
    (1968). For an intra-red method, see Delves & Williams (1966).

    The most sensitive methods for fenitrothion utilize gas
    chromatography with either a plasma-photometric detector (Bowman &
    Beroza, 1969) or a thermionic detector (Miyamoto et al., 1967);
    detection limits are usually 0.01-0.001 ppm.

    5.3.2  Other tests in cases of poisoning

    Levels of cholinesterase in the blood provide the most useful
    diagnosis of poisoning; for methods of estimation see: Michel (1949)
    and Stubbs (1960) for electrometric method, Ellman et al. (1961) for
    spectrophotometric method and Edson (1958) for tintometric method.

See Also:
        Fenitrothion (EHC 133, 1992)
        Fenitrothion (PIM 659)