WHO/Food Add./68.30



    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Working Party of Experts and the WHO Expert
    Committee on Pesticide Residues, which met in Rome, 4 - 11 December,
    1967. (FAO/WHO, 1968)

    Rome, 1968


    This pesticide was evaluated by the 1966 Joint Meeting of the FAO
    Working Party and the WHO Expert Committee on Pesticide Residues
    (FAO/WHO, 1967). Since the previous publication, additional
    information pertinent to evaluations for tolerances has become
    available and is summarized and discussed in the following monograph


    Other relevant chemical properties

    For use against insects in foods, phosphine is generated in situ from
    aluminum phosphide formulated with ammonium carbamate into tablets,
    pellets and granules. The release of phosphine is due to reaction
    between aluminum phosphide and moisture in the atmosphere. The rate of
    release of phosphine gas depends upon the formulation and physical
    condition of the aluminum phosphide, and on the temperature and
    moisture of the ambient air and the commodity being fumigated.

    Aluminum phosphide tablets generally used weigh 3 g each, and produce
    about 1 g of phosphine. The pellets weigh 0.6 g each and yield about
    0.2 g of the gas.

    Registered in 70 countries (Dieterich et al, 1967) and used fairly
    extensively in Argentina, Australia, Eastern Europe, India, Japan,
    Turkey and the United States. Manufacturers of principal product
    ("Phostoxin"(R)) estimate that 15 to 20 million metric tons of grain
    were treated in 1964.



    Pre-harvest treatments

    Not used on living plants.

    Post-harvest treatments

    Phosphine derived from aluminum phosphide has been used for the
    control of stored-product insects in many countries all over the world
    for the fumigation of raw cereal and processed cereal products, beans,
    peas, cottonseed meal, spices, dried vegetables and other foods and
    animal foods. The recommended dosage to 45 to 60 tablets or 165 to 200
    pellets/1,000 cu ft (28.3/m3) of space or 3 to 6 tablets/ton or 1,000
    kg of rain. The fumigation period varies with the temperature; 5 days
    at 54° - 59°F (12° - 15°C), 4 days at 60° - 68° (16° - 20°C), and 3
    days at 69°F (20°C) and above. Fumigation with aluminum phosphide is
    not recommended at temperatures below 40°F (5°C). For treating bulk
    grain and other raw commodities, the phosphine tablets or pellets are

    introduced into the stream of the commodity as it is being loaded into
    bins or freight cars, or the fumigant tablets or pellets are inserted
    into the commodity by a special probe. Bagged or packaged foods and
    feeds are fumigated either in some kind of an enclosure or under a
    gasproof sheet. The phosphine tablets or pellets are placed in trays
    located on, under, or in the stack of food; or the tablets can be
    pulverized and blown on the stack of packaged food which has been
    covered with paper. Sometimes the ground pellets are placed in
    moisture-permeable envelopes, and the envelopes are located on top of
    the stacked food or stapled to the sides of the enclosure. Aluminum
    phosphide must not come in contact with processed foods or feeds, and
    must not be placed in or attached to packages intended for consumers.
    All processed foods should be aerated for 48 hours before they are
    offered to the consumer.


    Milo fumigated with aluminum phosphide at the rate of 10 tablets/ton
    of grain had phosphine residues in one sample 11 and 16 days after
    treatment of 0.436 ppm and 0.209 ppm, respectively. In the second
    sample, the residues were 0.286 ppm and 0.085 ppm 7 and 11 days after
    treatment, respectively (Bruce, 1958 (unpublished)). Wagner and
    Fogleman (1962) reported no detectable phosphine residues in flour 24
    hours after treatment with aluminum phosphide.

    When fumigating processed foods, the aluminum phosphide or its
    decomposition products must not come in direct contact with the food.
    Any phosphine residue present in the food must, therefore, come from
    sorption of the phosphine gas. Using an indirect method for the
    analysis of phosphine residues, Mayr and Hild (unpublished) showed
    there was no evidence of phosphine absorption by or adsorption on any
    of the following foods after fumigation with aluminum phosphide at the
    recommended dosage rate : Barley, wheat, flour, oat flakes, noodles,
    rice, wheat bran, semolina, macaroni, dried apples, dried apricots,
    raisins, prunes, cottonseed cake, a variety of dog foods, peas,
    spinach, almonds, hazelnuts, peanuts, walnuts, coffee, tea, sugar
    lumps, chives, beans, lettuce, lentils, ground red and black pepper,
    curry powder, tumeric, marjoram, and potato flour. Although fresh
    vegetables are not customarily fumigated, these items were included to
    study any possible effects of the fumigation (Dieterich et al., 1967).

    Green coffee beans, cocoa powder, nonfat instant dry milk powder,
    malted barley flour, institutional doughnut mix, pie crust mix, oat
    flour, gluten concentrate, high fat soy flour, rice flour, gluten
    flour, bran buds, primary yeast, beet pulp, cornstarch, deer pellets,
    mink conditioner, raisins, dried apples and apricots, pecan pieces,
    corn flakes, rice breakfast food, and shredded wheat were fumigated at
    the recommended level and then aerated for 48 hours. The highest level
    of phosphine found in any product was 0.017 ppm (Dieterich et al,

    When phosphine was applied in a closed container to wheat, oats,
    barley, flax, and milled grain at concentrations of 0.15 - 0.60 mg/l,
    no detectable free PH3 was found even after accelerated aeration with
    nitrogen. However, there wereindications that under ideal laboratory
    conditions irreversible sorption may take place since chemisorbed PH3
    equivalent to 2.16 ppm was detected (Berck (unpublished)).


    In storage and processing

    The rate of evolution of phosphine from aluminum phosphide is
    dependent on atmospheric moisture. After short exposure periods (72
    hours or less), it is possible for residues of aluminum phosphide to
    be present in grain with a 9 per cent moisture content or below.
    However, such residues readily disappear during airing, turning and
    cleaning to which grain is normally submitted prior to milling
    (Heseltine and Thompson, 1957; Feuersenger, 1960; Liscombe, 1963).

    During studies of the affects of baking, no significant residues could
    be found in baked bread made of treated flour or flour from treated
    grain (Liscombe, 1963).


    The method developed by Bruce, Robbins, and Tuft (1962) hydrolyzes
    aluminum phosphide in the presence of dilute sulfuric acid to form
    phosphine. The liberated phosphine is driven out by nitrogen gas into
    scrubbers, and then the contents of the scrubbers are analyzed. This
    method is sensitive to less than 0.001 ppm [although previously stated
    to have a sensitivity of 0.01 ppm (FAO/WHO, 1967)].

    The method by Heseltine (1963) is based in part on the above method
    and depends upon reaction with acid potassium permanganate and a
    colorimetric determination of the phosphate as the blue reduction
    product of the phosphomolybdate. Accuracy for phosphine residues in
    grain is 0.01 ppm.


    Country                    Tolerance, ppm    Crop

    Bulgaria                   0                 Cereals

    Canada                     Negligible        Cereals and
                                                 processed foods

    CoMECo (i.e. Bulgaria,
    Roumania, U.S.S.R.,
    German Democratic
    Republic and Poland)       0.01              Corn

    Country                    Tolerance, ppm    Crop

    Czechoslovakia             0                 Cereals

                               0.01              Wheat

    Netherlands                0.1               Grain

    United States              0.1               Grain

                               0.01              Processed foods



    The 1966 Joint Meeting (FAO/WHO, 1967) concluded that phosphine
    aerates rapidly from treated foodstuff and a residue of 0.1 ppm in a
    raw cereal would yield a residue in bread and other food ready for
    consumption of a level at or below that which can be detected by
    current methods of analysis (0.01 ppm). Therefore, there was no
    necessity for an ADI figure. A tolerance of 0.1 ppm as PH3 on cereals
    was recommended.

    Considerable data are now available that show processed foods
    fumigated with aluminum phosphide according to good agricultural
    practice will have phosphine residues close to or below the
    sensitivity of the analytical methods presently used (0.01 to 0.001
    ppm). According to good agricultural practice the treated processed
    food shall be aerated for a minimum of 48 hours before it is offered
    to the public. Furthermore, under no condition shall the aluminum
    phosphide or its unreacted residues come in contact with the processed

    When used according to the above good agricultural practices, the
    following tolerances are recommended :

    Cereal products (only items to be cooked)
    vegetables, dried spices                               0.01 ppm

    Raw cereals                                            0.1 ppm


    Further work desirable

    It is desirable to have more data on the residues likely to result
    from the fumigation of cereal products, dried fruit, tree nuts, and
    other processed food that may be eaten without cooking. If there
    should be a need for a tolerance on any of these foods, the additional

    data will be used in subsequent meetings for determining the residue

    More data are also desirable on the phosphine residues in various food
    moving in commerce and on the amount of phosphine in total diet


    Bruce, R.B., Robbins, A.J., Tuft, T.O. (1962) Phosphine residues from
    Phostoxin treated grain. J. Agric. Food Chem., 10 : 18-21.

    Dieterich, W.H., Mayr, G., Hild, K., Sullivan, J.B., Murphy, J. (1967) 
    Hydrogen phosphide as a fumigant for foods, feeds, and processed food
    products. In Gunther, F.A., ed. Residue Reviews, 19 : 135-149.

    FAO/WHO. (1967) Evaluation of Some Pesticide Residues in Food. FAO
    Mtg. Rept. No. PL: CP/15; WHO/Food Add./67.32

    Feuersenger, M. (1960) Uber die Bestimmung von
    Schädlingsbekampfungsmitteln in Lebensmitteln. Bundesgesundheitsblatt
    (10): 149-1952.

    Heseltine, H.K. (1963) Detection and estimation of fumigants in
    air-determination of phosphine. In Pest Infestation Research, 
    p. 40-41.

    Heseltine, H., Thompson, R.H. (1957) The use of aluminum phosphide
    tablets for the fumigation of grain. Milling, Part 1 CXXIX (24): 676;
    Part 2 CXXIX (25): 730; Part 3 CXXIX (26) : 774.

    Liscombe, E.A.R. (1963) Hydrogen phosphide in tablet form as a grain
    fumigant. Research for Farmers, Can. Dept. Agric. (Summer 1963).

    Wagner, R.M., Fogleman, R.W. (1962) Determination of phosphine
    residues in commercial wheat flour. Unpublished report from
    Hazleton-Nuclear Science Corporation to Hollywood Termite Control Co.,
    Inc. (Jan. 9, 1962). 

    See Also:
       Toxicological Abbreviations
       Hydrogen phosphide (FAO/PL:CP/15)
       Hydrogen Phosphide (FAO/PL:1969/M/17/1)
       Hydrogen phosphide (WHO Pesticide Residues Series 1)