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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/77.24

                                                      ORIGINAL: ENGLISH






    DATA SHEETS ON PESTICIDES No. 24

    December 1976

    ZINC PHOSPHIDE






         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.

    Part 1 - General information

                                  CLASSIFICATION:

                                  Primary use:      Rodenticide

                                  Secondary uses:   None

                                  Chemical group:   Inorganic phosphide

                                  Data sheet No.:   24

                                  Date issued:      December 1976

    1.1  COMMON NAME - ZINC PHOSPHIDE

    Identity: Zn3 P2

    CHEMICAL STRUCTURE

    Synonyms:                   Local synonyms:

    1.2  SYNOPSIS

    A rodenticide of high mammalian toxicity which in the presence of
    dilute acid will decompose to liberate phosphine. It is not
    cumulative in body tissues.

    1.3  SELECTED PROPERTIES

    1.3.1  Physical characteristics

    A grey powder of high melting point which sublimes when heated in
    the absence of oxygen.

    1.3.2  Solubility

    Practically insoluble in water and ethanol. Soluble in benzene and
    carbon disulfide.

    1.3.3  Stability

    Stable when dry but decomposes slowly in moist air. It reacts
    violently with acids with decomposition to the spontaneously
    inflammable phosphine gas.

    1.3.4  Vapour pressure

    Very low. Phosphine odour detectable at 1.5-3.0 ml/m3 of air,
    depending on its purity.

    1.4  AGRICULTURE, HORTICULTURE AND FORESTRY

    1.4.1  Common formulations

    2.5% and 5% pastes for bait preparations. These are diluted with 10
    times their own weight of bait.

    1.4.2  Pests mainly controlled

    Mice, common rat, ship's rat, field mice, gophers, ground squirrels,
    prairie dogs.

    1.4.3  Use pattern

    Confined in most countries to trained personnel.

    1.4.4  Unintended effects

    Under exposed conditions toxicity is lost in about two weeks.

    1.5  PUBLIC HEALTH PROGRAMME

    Rodent control - see HOUSEHOLD USE

    1.6  HOUSEHOLD USE

    Rodent control. Under some circumstances secondary poisoning can
    result to cats eating freshly poisoned rodents.

    Part 2 - Toxicology and risks

    2.1  TOXICOLOGY - MAMMALS

    2.1.1  Absorption route:

    Absorbed by inhalation and from the gastrointestinal tract.

    2.1.2  Mode of action:

    Probably decomposes to phosphine in the stomach and is absorbed both
    as phosphine and as the phosphide. It has a toxic action on the
    heart, liver and kidneys. Death occurs from heart and kidney
    failure.

    2.1.3  Excretion products:

    Excreted in urine either as a hypophosphite or as dissolved
    phosphine. The presence of strong reducing substances in the urine
    is a common feature of poisoning with this material. Also, exhaled
    as phosphine from the lungs. Other metabolites include phosphoric
    acid and phosphate.

    2.1.4  Toxicity, single dose

    Oral: LD50 Rat(M)41 mg/kg.

    After a massive dose, death may occur in 70 minutes; with smaller
    doses, death may be delayed from 24 hours up to 2-3 days. Symptoms
    appear after 20-25 minutes. Animals become prostrate with deep slow
    respiration, finally terminating in convulsions. Posture at death is
    characteristic: animals are found on their bellies with legs and
    tail spread out.

    Dermal: No information.

    2.1.5  Toxicity, repeated doses

    Oral: After repeated doses, kidney damage and hyaline degeneration
    of the myocardium was observed. Livers showed cloudy swelling,
    hyaline degeneration and necrosis usually located in the centre of
    the lobules.

    Inhalation

    No information. However, inhalation of phosphine gas or dust would
    be hazardous. See 2.2.2 below for relevant human data.

    Cumulation of compound:

    Zinc phosphide is not cumulative in any body tissues.

    Cumulation of effect:

    In case of repeated exposure, there is cumulation of effect
    resulting in liver, kidney and lung damage.

    2.1.6  Dietary studies

    Short-term: Six rats were fed a diet containing 300 ppm zinc
    phosphide. During the first week weight gains were markedly reduced
    and all six died during the second week of feeding. A further group
    of six rats were fed zinc phosphide 200 ppm for one month. Two
    deaths were recorded in the second week and weight gains were half
    that of the controls over the feeding period. Histopathology
    revealed liver damage in the peripheral and central lobular areas.
    The lungs showed evidence of congestion with haemorrhage or exudate
    in the alveolar spaces.

    Long-term: No information.

    2.1.7  Supplementary studies of toxicity

    Carcinogenicity

    No information available.

    Teratogenicity

    No information available.

    2.1.8  Modifications of toxicity

    Experiments in dogs have shown that zinc phosphide has a low
    toxicity on these animals unless it is combined with a dilute acid
    or following the stimulation of normal gastric secretion. Under
    these circumstances phosphine is liberated in the stomach.

    2.2  TOXICOLOGY - MAN

    2.2.1  Absorption

    Absorbed from the gastrointestinal tract. It can also be absorbed by
    inhalation of dust or of liberated phosphine gas. Does not appear to
    be absorbed through the intact skin, but can be absorbed through
    abrasions in the skin.

    2.2.2  Dangerous doses

    Single: A dose of 5 g has caused death. However a 50 g dose has
    been survived. Toxicity is lessened if vomiting occurs soon after
    ingestion. Phosphine gas can be hazardous to rodent control
    officers. 2.8 mg/litre of air is rapidly fatal in less than 30
    minutes, but levels of 0.14-0.26 can be withstood for 30-60 minutes
    without consequences.

    Repeated: Doses in the region of 100 mg daily appear to be
    harmless, though 30 mg has been stated to cause nausea.


    2.2.3  Observations of occupationally exposed workers

    The safety record of this compound has been good; one industrial
    accident has been reported involving three cases.

    2.2.4  Observations on exposure of the general population

    Cases of poisoning, both accidental and intentional have resulted
    from ingestion of zinc phosphide, see 2.2.6 below.

    2.2.5  Observations on volunteers

    Volunteers who ate three geese poisoned with zinc phosphide over a
    period of two days were unaffected on the first day. However, on the
    second day two of the three volunteers suffered from stomach pains
    and diarrhoea.

    2.2.6  Reported mishaps

    Twelve children were poisoned by eating contaminated barley. Several
    cases of poisoning have occurred as domestic accidents. Between 1917
    and 1965, 26 fatalities have been reported from zinc phosphide
    poisoning, of which 18 were suicides.

    2.3  TOXICITY TO NON-MAMMALIAN SPECIES

    2.3.1  Fish

    No data available but presumably toxic.

    2.3.2  Birds

    Very toxic.

    2.3.3  Other species

    Very toxic to cows, goats, sheep, pigs, wild rabbits.

    Part 3 - For regulatory authorities

    RECOMMENDATIONS ON REGULATION OF COMPOUND

    3.1  RECOMMENDED RESTRICTIONS ON AVAILABILITY

    (For definition of categories, see introduction.)

    All formulations, category 2

    3.2  TRANSPORTATION AND STORAGE

    All formulations: United Nations Classification 6.1 for all
    formulations. Should be stored in clearly labelled, hermetically
    sealed impermeable containers away from oxidizing agents, acids and
    living quarters, under lock and key, secure from access by
    unauthorized persons and children. They must not be stored in damp
    conditions or be allowed to become damp, as in these circumstances
    there is both a toxic and fire hazard. No food or drink should be
    stored in the same compartment.

    3.3  HANDLING

    All formulations: 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. Baits of zinc
    phosphide should be removed and the area thoroughly cleaned up after
    the necessary purpose has been fulfilled.

    3.4  DISPOSAL AND/OR DECONTAMINATION OF CONTAINER

    All formulations:

    Containers must either be crushed and buried below the topsoil or
    burned. Care must be taken to avoid subsequent contamination of
    water sources. Decontamination of containers in order to use them
    for other purposes should not be permitted.

    3.5  SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS

    All formulations:

    Pre-employment and periodic 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.

    3.6  ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT

    All formulations

    Not applicable.

    3.7  LABELLING

    All formulations

    Minimum cautionary statement "POISON" (skull and crossbones
    insignia).

    Zinc phosphide is a very toxic substance. Do not inhale dust or
    fumes. Keep this material or baits containing it, out of reach of
    children and domestic animals and well away from foodstuffs, animal
    feed and their containers. Keep dry and away from acids of all
    kinds.

    3.8  RESIDUES IN FOOD

    If used correctly as a bit, residues of zinc phosphide will not
    appear in human food.

    3.8.1  Maximum residue levels

    Levels for zinc phosphide have not been recommended by the joint
    FAO/WHO meeting on Pesticide Residues.

    Part 4 - Prevention of poisoning in man and emergency aid

    4.1  PRECAUTIONS IN USE

    4.1.1  General

    Zinc phosphide is a rodenticide of high toxicity. It is readily
    absorbed from the gastrointestinal tract and dusts may be absorbed
    by inhalation. In addition it may decompose to liberate phosphine
    gas which is extremely hazardous. It is not readily absorbed through
    the intact skin.

    4.1.2  Manufacture and formulation

    T.L.V.

    For phosphine gas, PH3 (AGGIH) 0.4 mg/m3 (USSR) 0.1 mg/m3.

    Closed system 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

    Particularly when opening container and when mixing, protective
    impermeable boots, clean overalls, gloves and a face mask should be
    worn. Mixing, if not mechanical, should always be carried out with a
    paddle of appropriate length. The applicator should avoid inhaling
    dust particles and avoid contact with the mouth. Particular care is
    needed when the 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.

    Zinc phosphide baits should not be used where there is a risk of
    contaminating food, animal feeding stuffs or drinking or washing
    water. Exposed baits should be laid in containers clearly marked
    "Poison". Baits should not be laid unless all access by children and
    animals other than rats and mice can be prevented. Except in locked
    unoccupied premises, baits should not remain down for more than 24
    hours. All exposed baits and their containers should be removed
    after treatment and burned. Rodent bodies should be searched for and
    destroyed by burning.

    4.1.4  Other associated workers (including flagmen in aerial
           operations)

    Not applicable.

    4.1.5  Other populations likely to be affected

    With correct use as described under mixers and applicators (4.1.3
    above) other populations should not be exposed to hazardous amounts
    of zinc phosphide.

    4.2  ENTRY OF PERSONS INTO TREATED AREAS

    The general public should be excluded from all access to premises
    while baits are exposed.

    4.3  SAFE DISPOSAL OF CONTAINERS AND SPILLAGE

    Residues in containers should be emptied in a diluted form into a
    deep pit, taking care to avoid contamination of ground waters.
    Decontamination of containers in order to use them for other
    purposes should not be permitted. Spillage should be removed as much
    as possible into a deep dry pit and the remainder washed away with
    large quantities of water. It should be borne in mind during these
    operations that in the presence of water, phosphine gas will be
    liberated and therefore a respirator may be advisable.

    4.4  EMERGENCY AID

    4.4.1  Early symptoms of poisoning

    After ingestion there is a latent period of approximately one hour.
    Earliest symptoms are usually nausea, abdominal pain, chest
    tightness, excitement, and agitation and a feeling of chilliness and
    of being "cold all over". Vomiting is constant. Shock, early
    dyspnoea, thirst, oliguria, convulsions or coma have been observed.

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

    If swallowed, vomiting should be induced if the person is conscious.
    Complete rest and quiet are indicated.

    Part 5 - For medical and laboratory personnel

    5.1  MEDICAL DIAGNOSIS AND TREATMENT OF CASES OF POISONING

    5.1.1  General information

    Zinc phosphide is a compound of high toxicity normally used in bait
    form as a rodenticide.

    It is readily absorbed by the gastrointestinal tract and may be
    absorbed by inhalation in dust form or as phosphine gas. Although it
    is not absorbed through the unbroken skin, it may be absorbed
    through cuts or abrasions. Its toxicity is related to its liberation
    of phosphine on decomposition, following absorption. Organs that may
    be affected include the heart, lung, liver and kidney.

    5.1.2  Symptoms and signs

    There is a latent period of about 60 minutes following ingestion and
    the appearance of symptoms. Earliest symptoms are usually nausea,
    abdominal pain, chest tightness, excitement and agitation and a
    feeling of chilliness, of being "cold all over". Vomiting is
    constant. Later symptoms may include shock, dyspnoea, thirst,
    oliguria and kidney failure, convulsions and coma. Purpura and
    asymptomatic thrombocytopenia have been observed. Early deaths may
    occur from pulmonary oedema. The majority of fatal cases die after
    30 hours as a result of cardiac damage.

    5.1.3  Laboratory

    There are no simple tests to confirm exposure. However, the
    patient's breath may smell of phosphine (garlic odour). Serum zinc
    levels will be raised and the urine will contain reducing
    substances, which may be hypophosphite, dissolved phosphine or due
    to zinc glycosuria. If stomach aspiration is performed a black fluid
    with a pungent smell of phosphine is typical of ingestion of this
    compound. Circulating methemalbumin has also been observed.

    5.1.4  Treatment

    Treatment is mainly symptomatic. Vomiting should be induced
    immediately followed by gastric lavage with 2-4 litres of water. It
    is important to clear zinc phosphide from the gastrointestinal
    tract, with non-oily purgatives if absorption of zinc phosphide
    particles is to be avoided. Correction of fluid loss and electrolyte
    disturbances is important.

    Two suggested treatments are the use of 0.5 gm of copper sulfate (as
    a 1% aqueous solution) which has the additional theoretical benefit
    of forming insoluble copper phosphide, or gastric lavage with a 1 in
    1000 potassium permanganate solution, which has been suggested as a
    means of oxidizing the phosphide.

    5.1.5  Prognosis

    Early vomiting improves the prognosis. If the patient survives for
    three days the further outlook is good. However, no patient who has
    experienced shock has yet survived.

    5.1.6  References of previously reported cases

    The following review covers poisoning cases with zinc phosphide
    reported in Europe and gives a detailed case history.

    (a) Stephenson, J. B. (1967) Archives of Environmental Health, 15,
    83-88

    (b) Van Oettingen, E. W., The toxicity and potential dangers of zinc
    phosphide and of hydrogen phosphide, Public Health Report 203,
    1.1947

    (c) Frketic, J., Magdic, A. & Stajduhor-Djuric, Z., Otravanja
    cinkovrim fosfidom Arh. Hig. Rada., 8.15.1957

    5.2  SURVEILLANCE METHODS

    There are no readily available surveillance procedures.

    5.3  LABORATORY METHODS

    References only are given.

    5.3.1  Detection and analysis

    Microdistillation of liver and reaction of the phosphorous with
    silver nitrate to form silver phosphide using paper electrophoresis.
    Curry, A. S. et al., J. Pharm. Pharmacol., 10:635, 1958.

    A sophisticated method involving neutron activation analysis for the
    determination of phosphides and white phosphorous in biological
    materials has been published. Krishnan, S.S. et al., Anal. Chem.,
    42(6), 557-560, 1970.

    A method involving gas chromatography is reported by Robinson, W. H.
    et al., J. Ag. Food Chem., 19(5), 875-8, 1971.

    5.3.2  Other tests in cases of poisoning

    These include measurement of serum zinc levels, estimation of urine
    reducing substances, and estimation of methaemoglobin.



    See Also:
       Toxicological Abbreviations
       Zinc phosphide (ICSC)