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    WORLD HEALTH ORGANIZATION             FOOD AND AGRICULTURE
                                          ORGANIZATION
    ORGANISATION MONDIALE DE LA SANTE     ORGANISATION POUR L'ALIMENTATION
                                          ET L'AGRICULTURE

                                                      VBC/DS/83.48

                                                      ORIGINAL: ENGLISH






    DATA SHEETS ON PESTICIDES No. 48

    PHENTHOATE






         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     rsum 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 Sant.

                           CLASSIFICATION:

                           Primary use: Insecticide

                           Secondary use: Acaricide/Scalicide/Thripicide

                           Chemical group: Organophosphorus compound

    1.  GENERAL INFORMATION

    1.1  COMMON NAME:

    Phenthoate (ISO, BSI, exception; JMAF-PAP)

    1.1.1  Identity:

    IUPAC S-alpha-ethoxycarbonylbenzyl O,O-dimethyl phosphorodithioate

    CAS No. 1 Acetic acid, mercaptophenyl-ethyl ester, S-ester with
    O,O-dimethyl phosphorodithioate

    CAS Reg. No. 2597-03-07

    Molecular formula C12H17O4PS2

    Molecular weight 320.3

    CHEMICAL STRUCTURE

    1.1.2  Synonyms:

    Bay 33051, Bayer 18510, CidemulR, CidialR,
    dimephenthioate,dimephenthoate, dimethenthoate, ElsanR, ENT 23438,
    ENT 27386, ErucinR, ErusanR, fenthoate, L-561, OMS 1075, PAPR,
    PapthionR, PhendalR, RogdialR, S-2940, TanoneR, TH 346-1,
    TsidialR.

    1.2  SYNOPSIS

    Phenthoate is a broad spectrum, non-cumulative, organophosphorus
    pesticide; a cholinesterase inhibitor with contact and stomach
    action; moderately toxic to mammals with no residual activity.
    Toxicity is increased after metabolism to the oxygen analogue.
    Phenthoate is phytotoxic to some plants.

    1.3  SELECTED PROPERTIES

    1.3.1  Physical characteristics

    The pure substance is a colourless crystalline solid; the technical
    product is a reddish-yellow, oily liquid. Both have an aromatic
    odour. The melting point is 17-18C; the density (d420) is
    1.226; the refraction index (nD20) is 1.5550; the flash point
    (cleveland) is 165-170C (technical product). Neither the pure
    substance nor the technical product is corrosive.

    1.3.2  Solubility

    water (pure compound)                        11 mg/l, 24C
    water (technical product)                   200 mg/l, 20C
    N-hexane (technical product)                 120 g/l, 20C
    1,2-diethoxyethane (technical product)       200 g/l, 20C
    petroleum ether (technical product)         170  g/l, 20C
    light petroleum (technical product)         100  g/l, 20C

    1.3.3  Stability

    It is stable in acid or neutral solutions; in alkali solutions
    hydrolysis occurs, at pH 8.0 the half-life is 12 days. It is
    thermally unstable; at room temperatures the shelf-life is several
    months; at 50C it is degraded in 110 hours. Solar energy and
    aerobic conditions promote volatization and loss from exposed
    surfaces. Humidity probably does not directly affect decomposition,
    on moist grain over 80% of applied material remains after one year
    of storage. Decomposition of soil-applied phenthoate is due to
    microbial action with CO2 as the end product.

    1.3.4  Vapour pressure

    5.33 x 10-6 kPa (4 x 10-5 mmHg) at 40C.

    1.4  AGRICULTURE, HORTICULTURE AND FORESTRY

    1.4.1  Common formulations

    Emulsifiable concentrates (500-850 g tech./kg); oil solutions (50 g
    tech. in 800 g mineral oil); wettable powder (400 g/kg); dust
    (30 g/kg); granules (20 g/kg); ULV spray (1 kg/kg).

    1.4.2  Pests mainly controlled

    Lepidoptera, jassids, aphids and soft scales; mosquito larvae and
    adults; blowflies and various strains of houseflies; and ked.

    1.4.3  Use pattern

    It is used to protect cotton, rice, fruit and vegetable crops, and
    ornamental plants. It is used on animals to protect against external
    parasites; on and around agricultural structures to control nuisance
    and disease vector insects.

    1.4.4  Unintended effects

    Phytotoxic to some grapes, figs, and chinese cabbage at upper range
    of concentration. Discolouration of apples has also been reported.

    1.5  PUBLIC HEALTH PROGRAMMES

    1.5.1  Common formulations

    Emulsifiable concentrates (500-850 g/kg); ULV sprays (1 kg/kg).

    1.5.2  Pests mainly controlled

    Mosquitos (larvae and adults), houseflies; experimental application
    on clothing against human body lice has proved effective.

    1.5.3  Use pattern

    As recommended by manufacturer.

    1.6  HOUSEHOLD USE

    No recommended uses.

    2.  TOXICOLOGY AND RISKS

    2.1  TOXICOLOGY - MAMMALS

    2.1.1  Absorption route

    Absorbed from the gastrointestinal tract; by inhalation; and through
    the intact skin.

    2.1.2  Mode of action

    Cholinesterase inhibition after metabolism. Orally administered
    phenthoate is readily converted to phenthoate-oxon, which is the
    active form, by liver microsomal enzymes.

    2.1.3  Excretion products

    A study of the 24-hour cumulative distribution of 32P_ and
    14C-phenthoate in the white mouse following a single oral dose
    shows that 85-94% of the radioactivity is excreted in the urine,
    5-13% in the faeces. Unchanged phenthoate accounts for less than 3%
    of total excreted radioactivity and was found in faeces only; no
    phenthoate-oxon was detected in either faeces or urine, though
    significant levels of its non-toxic metabolites were. The selective
    toxicity of phenthoate to insects is attributed to the accumulation
    of the oxon form.

    2.1.4  Toxicity single dose

    Oral:  LD50 rat               400 mg/kga (240-400 mg/kg)
                mouse         350-400 mg/kg
                guinea-pig        377 mg/kg
                rabbit            210 mg/kg
                hare               72 mg/kg
                dog               500 mg/kg

    Dermal: LD50 rat           > 4000 mg/kg (2000-6750 mg/kg)


                
    aThe WHO accepted value for the rat acute oral LD50, 400 mg/kg,
    is used here; the lower range values probably reflect the effect of
    toxic impurities found in earlier technical preparation (see section
    2.1.8).

    2.1.5  Toxicity repeated doses

    Oral: No information.

    Dermal: No information.

    Inhalation: No information.

    Cumulation: No information.

    2.1.6  Dietary studies

    Short-term: No information.

    Long-term: In an 88-week rat study the highest non-toxic dose was
    established to be 0.5 (mg/kg)/day.

    2.1.7  Supplementary studies of toxicity

    Carcinogenicity: No information. 

    Teratosenicity: No information.

    Reproduction: No information.

    Neurotoxicity: No information.

    Mutagenicity: Phenthoate has been shown to be non-mutagenic in two
    microbial studies involving several strains of Salmonella
    typhimurium and Escherichia coli.

    2.1.8  Modifications of toxicity

    In mammals potentiation of toxicity occurs with several impurities
    found in early preparations of the technical product. These
    impurities affect homeotherm toxicity but in heterotherms they have
    no potentiation effect. The impurities include:

    (MeO)2P(S)CH(C6H5) COOH              coded APH

    (MeO)2 P (S) (SMe)                   coded TES

    (MeO)2P(O) (SMe)                     coded OTE

    (MeO)2P(O)SCH(C6H5)COOC2H5           coded OPH
    (MeS)2P(O)(OME)                      coded ITE
    (MeO)(MeS)P(O)SCH(C6H5)COOC2H5       coded IPH

    2.2  TOXICOLOGY - MAN

    2.2.1  Absorption route

    Absorbed from the gastrointestinal tract; by inhalation; and through
    the intact skin.

    2.2.2  Dangerous doses

    Single:  No information.

    Repeated: No information.

    2.2.3  Observations of occupationally exposed workers

    Spraymen in a WHO supervised spray programme showed no ill-effects
    over an extended period of spraying. Whole blood cholinesterase
    levels were 90% of normal after three days of spraying (tintometric
    method).

    2.2.4  Observations on exposure of the general population

    The population in villages undergoing WHO supervised spraying showed
    no signs or symptoms for a 15-day observation period. No inhibition
    of whole blood cholinesterase occurred (tintometric method).

    2.2.5  Observations of volunteers

    Young adult male military recruits wearing garments with sleeves
    treated with 1% phenthoate for six weeks, 34-48 hours/week, showed
    no noticeable ill-effects.

    2.2.6  Reported mishaps

    No information.

    2.3  TOXICITY TO NON-MAMMALIAN SPECIES

    2.3.1  Fish

    Toxic. Phenthoate has been implicated in at least three large-scale
    accidental fish kills in fresh water containing measurable levels of
    phenthoate (0.001-0.002 mg/l). Goby, grey mullet and rainbow trout
    body concentrations were 0.03-0.09 mg/kg.

    LC100 (96 hours) - goldfish           4.5 mg/l
                       minnows            3.4 mg/l
                       mosquito-fish      0.3 mg/l
                       guppies          2-3.0 mg/l

    2.3.2  Birds

    Toxic. Oral acute LD50 - pheasants  218 mg/kg
                             quail      300 mg/kg

    2.3.3  Other species

    Toxic to honey-bees - not recommended for spraying in vicinity of
    bee colony nectar gathering areas. Phenthoate possesses no repellent
    properties.

    Acute LD50 honey-bee 0.12 mg/bee
    Acute LD90 honey-bee 0.40 mg/bee
    Toxic to snakes
    Toxic to nuisance insects, e.g., midges (Chironomidae)
    LC50 midge larvae 0.0019-0.0053 mg/l
    LC90 midge larvae 0.0054-0.0150 mg/l

    3.  FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF
        COMPOUND

    3.1  RECOMMENDED RESTRICTIONS ON AVAILABILITY

    (For definitions of categories see Introduction to data sheets)

    Liquids over 20%: category 3. Other liquids and solids over 8%:
    category 4. All other solids: category 5.

    3.2  TRANSPORTATION AND STORAGE

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

    Formulations in category 5 - Should be transported and stored in
    clearly marked leakproof containers, out of reach of children and
    away from food and drink.

    3.3  HANDLING

    Formulations in categories 3 and 4 - Protective clothing (see
    section 4) should be used by all 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 and after handling before
    washing of hands and face.

    Formulations in category 5 - The same facilities required as those
    needed for the handling of any chemical.

    3.4  DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS

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

    3.5  SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS

    Formulations in categories 3 and 4 - Pre-employment medical
    examinations of workers is desirable. Workers suffering from active
    hepatic or renal disease should be excluded from contact.
    Pre-employment and periodic cholinesterase test for workers
    desirable, especially for those handling concentrates. Special
    account should be taken of the workers' mental ability to comprehend
    and follow instructions. Training of workers in techniques to avoid
    contact is essential.

    Formulations in category 5 - Warning of workers to minimize
    contact is essential.

    3.6  ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT

    All formulations - Pilot and loaders should have special training
    in application methods and early warning symptoms of poisoning, and
    they must wear a suitable respirator. Flagmen should wear overalls,
    an impermeable brimmed hat, and be located well away from the
    dropping zone.

    3.7 LABELLING

    Formulations in categories 3 and 4 - Minimum cautionary statement
    - Phenthoate is an organophosphorus compound that inhibits
    cholinesterase. It is poisonous if swallowed. It may be absorbed
    through the skin. Avoid skin contact; wear hand protection, clean
    protective clothing and a respirator when handling the 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. If poisoning occurs, call a physician.
    Atropine and pralidoxime are specific antidotes and artificial
    respiration may be needed.

    Formulations in category 5 - Minimum cautionary statement - This
    formulation contains phenthoate which is a toxic substance. Keep the
    material out of reach of children and well away from foodstuffs,
    animal feeds and their containers.

    3.8  RESIDUES IN FOOD

    Maximum residue limits have been recommended for phenthoate by the
    Joint FAO/WHO Meeting on Pesticide Residues. These are subject to
    change at annual reviews.

    4.  PREVENTION OF POISONING IN MAN AND EMERGENCY AID

    4.1  PRECAUTIONS IN USE

    4.1.1  General

    Phenthoate is an organophosphorus pesticide of moderate toxicity. It
    is readily absorbed through the intact skin, from the
    gastrointestinal tract and by inhalation. Repeated exposure may have
    a cumulative effect on cholinesterase levels.

    4.1.2  Manufacture and formulation TLV

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

    4.1.3  Mixers and applicators

    When opening the container and when mixing, protective impermeable
    boots, clean overalls, gloves and 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
    hat, 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 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.

    4.1.4  Other associated workers (including flagmen in aerial
           operations)

    Persons exposed to phenthoate and associated with its application
    should wear protective clothing and observe the precautions
    described above in section 4.1.3 under "mixers and applicators".

    4.1.5  Other populations likely to be affected

    With good application practice, subject to section 4.2 below, other
    persons should not be exposed to hazardous amounts of phenthoate.

    4.2  ENTRY OF PERSONS INTO TREATED AREA

    Unprotected persons should be kept out of tall crops for four days
    and out of other crops for 24 hours.

    4.3  DECONTAMINATION OF SPILLAGE AND CONTAINERS

    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. 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 should be provided for the rinsings.
    Decontaminated containers should not be used for food and drink.
    Spillage of phenthoate and its formulations should be removed by
    washing with 5% sodium hydroxide solution and then rinsing with
    large quantities of water.

    4.4  EMERGENCY AID

    4.4.1  Early symptoms of poisoning

    Early symptoms of poisoning may include excessive sweating,
    headache, weakness, giddiness, nausea, vomiting, hypersalivation,
    stomach pains, blurred vision, slurred speech and muscle twitching.
    Later there may be convulsions and coma.

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

    5.  FOR MEDICAL AND LABORATORY PERSONNEL

    5.1  MEDICAL DIAGNOSIS AND TREATMENT IN CASES OF POISONING

    5.1.1  General information

    Phenthoate is an organophosphorus pesticide of moderate mammalian
    toxicity which is active against a variety of agricultural and
    public health pests. It is readily absorbed from the
    gastrointestinal tract; through the intact skin; and by inhalation.
    It is converted in vivo to the oxygen analogue phenthoate-oxon
    which inhibits cholinesterase. It does not accumulate in body
    tissues.

    5.1.2  Symptoms and signs

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

    5.1.3  Laboratory

    The most important finding is reduction of activity of blood
    cholinesterases. Urinary levels of organic phosphorus containing
    metabolites may also be used as a measure of exposure. Neither
    method is specific for phenthoate.

    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 large quantities of 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 by intravenous injection and 1000 mg 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.

    Diazepam may be given to control convulsions. 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 given 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 CNS stimulants of all kinds. Pralidoxime and
    toxogonin are not regarded as effective antidotes in phenthoate
    poisoning.

    5.1.5  Prognosis

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

    5.1.6  References of previously reported cases

    Phenthoate has been implicated in a number of cases of pesticide
    poisoning, see WHO, VBC/TOX/77.20.

    5.2  SURVEILLANCE TESTS

    
                                                                                       

    Test                          Normal          Action           Symptomatic
                                  levela          levela           levela
                                                                                       

    Plasma cholinesterase          100%             50%             Variable

    Whole blood or
    erythrocyte cholinesterase     100%             70%             Usually 40%
                                                                                       

    aExpressed at percentage of pre-exposure activity.

    
    5.3  LABORATORY METHODS

    5.3.1  Detection and assay of compounds

    Thin-layer chromatography and gas-liquid chromatography methods have
    been used to analyse phenthoate in technical products and in its
    formulations. Analysis of residues in plant and animal tissues
    gas chromatography and flame photometry methods. See Bazzi, B.
    (1976) Anal. Methods Pestic. Plant Growth Regul., 8, 159

    5.3.2  Other tests in case of poisoning

    Levels of cholinesterase in the blood, particularly plasma, provide
    the most useful diagnosis of poisoning. Michel, N. O. (1949)
    J. Lab. Clin. Med., 34, 1564-1568. Ellman, G. L. et al. (1961)
    Biochem. Pharmacol., 7, 88-95.

    Measurement of urine metabolites may also be determined in order to
    give an indication of exposure for methods. See section 5.3.1,
    Detection and assay.

                                    = = =



    See Also:
       Toxicological Abbreviations
       Phenthoate (Pesticide residues in food: 1980 evaluations)
       Phenthoate (Pesticide residues in food: 1981 evaluations)
       Phenthoate (Pesticide residues in food: 1984 evaluations)