FAO, PL:CP/15
    WHO/Food Add./67.32


    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Working Party and the WHO Expert Committee on
    Pesticide Residues, which met in Geneva, 14-21 November 1966.1

    1 Report of a Joint Meeting of the FAO Working Party and the WHO
    Expert Committee on Pesticide Residues, FAO Agricultural Studies, in
    press; Wld Hlth Org. techn. Rep. Ser., 1967, in press








    The data here considered refer to hydrogen phosphide from tablets or
    similar formulations based upon aluminium phosphide from which the gas
    is released on exposure to moist atmosphere.


    Acute toxicity

    Animal        Route     Concentration   Death occurred after the      References
                                            following time of exposure

    Rat           inhal.    0.68 mg/l       65-75 min.                    Neubert &

    Rat           inhal.    1.47 mg/l       35-50 min.                    Neubert &

    Rat, rabbit   inhal.    0.2-1%          30 min.                       Laue, 1954

    Rabbit        inhal.    10 ppm          120 min. daily, during 2      Harger &
                                            days                          Spolyar, 1958

    Guinea-pig    inhal.    25 ppm          4 hr daily, during 2 days     Harger  &
                                                                          Spolyar, 1958

    Mouse         inhal.    50 ppm          2 hr daily, during 1 day      Harger &
                                                                          Spolyar, 1958

    Cat           inhal.    25 ppm          2, 3 to 4 hr daily, during    Harger &
                                            3 days                        Spolyar, 1958
    Hydrogen phosphide is a very toxic gas with a cumulative effect. There
    are no data available on the acute LD50 of phosphide. The LD50 for
    rats of the related compound zinc phosphide is 40.5 + 2.9 mg/kg
    (Johnson & Voss, 1952).

    Man. 2.8 mg hydrogen phosphide/l of air are lethal for man in a
    short time (Flury & Zernik, 1931).

    The threshold limit for hydrogen phosphide is set at 0.4 mg/m3
    (Anon., 1964).

    Short-term and long-term studies

    It is reported that rats, fed with grain which had been fumigated at
    excessive dosages, showed no ill effects, even when the grain was not
    cleaned before consumption (Schulemann, 1953).


    If this fumigant is proposed for use on foods other than cereals,
    further work is required to establish that no residues left. If,
    however, residues are left and cannot be removed, adequate
    toxicological studies should be performed.


    Cereals treated with aluminium phosphide must be properly cleaned and
    washed before being processed for food, so that no residue of powder
    derived from the fumigant material reaches the consumer.


    Use pattern

    (a) Pre-harvest treatments

    Hydrogen phosphide in not used on living plants.

    (b) Post-harvest treatments

    Hydrogen phosphide is used for controlling insects mainly in grain and
    other cereals; but also in legumes and many other dry stored foods.
    The tablets are applied as the grain or other foodstuff is being
    loaded into bins or box cars, or by insertion whilst the foodstuff is
    standing in bins or warehouses. Treatments must be undertaken in grain
    bins, or some other kind of enclosure. Gas-proof sheets are sometimes
    used to cover stacks of bagged foodstuffs in warehouses. Comparatively
    recently the use of hydrogen phosphide has been extended to animal
    feeds and processed food for human consumption, subject to
    recommendations that no unreacted aluminium phosphide will come into
    contact with such food and that none of the food be offered to the

    consumer before 48 hours airing has taken place. These foods include
    certain items (e.g. dried fruits, nuts) which might be eaten without

    (c) Other uses

    Phosphine as an insecticide is only used as in (b).

    (d) Extent of use

    Phosphine tablets are registered and used in very many countries, but
    fairly extensively in Argentine, Australia, Eastern Europe, India,
    Japan, South Africa and Turkey. The manufacturers of the principal
    proprietary product ("Phostoxin") estimate that 15 to 20 million
    metric tons of grain were treated in 1964.

    Tolerances (established or considered)

    Comeco (i.e. Bulgaria,        - Cereals      0.1  ppm
    Roumania, USSR, German 
    Democratic Republic and

    Czechoslovakia                - Cereals      0.1  ppm
                                  - Wheat        0.01 ppm

    Netherlands                   - Grain        0.1  ppm

    Canada                        - Grain        0.1  ppm

    USA                           - Grain        0.1  ppm

    In the USA and Canada petitions have been made to establish a
    tolerance of 0.1 ppm of hydrogen phosphide in various processed
    foodstuffs including flour and other cereal products, dried fruits
    and dried milk.

    Residues resulting from supervised trials

    In the Netherlands wheat was fumigated in a dose of three, four,
    five and six tablets PHOSTOXIN per m3 grain. After this fumigation
    the grain was aerated during 48 hours. Analysis after 12 days showed
    residues which were under the 0.005 ppm level. Similar results were
    obtained in Germany after the exposure over a period, from 48 hours up
    to 30 days, of wheat, wheat flour, oats and rice (Unpublished

    Wheat, corn and milo were fumigated in the USA at the maximum
    recommended rate and with four times this rate of application.
    Experiments were also made to determine the effects of high and low
    temperatures, aeration, fumigation of cracked grain, fumigation in

    sealed containers and re-fumigation of previously treated grain. The
    results showed that the residues almost completely disappeared, within
    12 days after the application. Only in sealed containers were high
    residues (up to 3 ppm) obtained. After exposure to air the residues
    disappeared within 12 days. (Cogburn & Tilton, 1963; Lindgren, Vincent
    & Strong, 1958; McGregor, 1961; Strong & Lindgren, 1960.)

    Wheat fumigated under practical conditions revealed a maximum residue
    of 0.016 ppm just after turning but not aerating. After aerating the
    residue dropped to 0.006 ppm. Analyses were made one to 14 days after
    treatment of the grain (Bruce, Robbins & Tuft, 1962).

    Residues in food moving in commerce

    In 99 samples taken at time of import from cargoes shipped from all
    over the world to Rotterdam and Amsterdam the amount of insecticide
    was determined. One sample showed a residue of 0.3 ppm. The rest of
    the investigated samples showed a maximum residue of 0.04 ppm, using a
    method with a limit of sensitivity of 0.01 ppm (Phytopharmacy
    Committee, Netherlands, 1966).

    Investigations carried out on arrival of treated grain in the United
    Kingdom showed residues below 0.1 ppm on grain treated with phosphine.

    Residues at time of consumption

    Various workers have shown that most of the phosphine present in
    foodstuffs at the termination of the period of exposure to the
    fumigant is very loosely held. For example, flour which at the
    termination of an experimental fumigation at a high dosage contained
    nearly 700 parts per million, gave less than 0.1 ppm after 24 hours
    free exposure to the air (Degesch, Unpublished report).

    The rate of evolution of phosphine from aluminum phosphide is
    dependant on atmospheric moisture. After short periods of exposure
    (e.g. 72 hours or less) at very low moisture contents (e.g. grain of
    below nine per cent water content) it is possible for residues of
    aluminium phosphide to be present. However such residues readily
    disappear during the airing turning and cleaning to which grain is
    normally submitted prior to milling (Heseltine & Thompson, 1957;
    Feursinger, 1960).

    In studies of the effects of baking no significant residues could be
    found in bread baked from grain or flour which had been treated
    (Bruce, Robbins & Tuft, 1962). The vitamin A and B2 contents of
    wheat germ and whole meal flour were not affected by fumigation with
    hydrogen phosphide. The differences between untreated and treated were
    within the limit of the natural variation. Extension of the exposure
    time up to five days did not affect this result (Unpublished report
    from Degesch).

    Methods of residue analysis

    Residues of phosphine may be removed from cereals and similar
    foodstuffs for analysis with a stream of nitrogen or other inert gas,
    as described by White & Bushey (1949) or Diemair (1954). The method of
    Bruce, Robbins & Tuft (1962) in which phosphine is oxidized to
    phosphate with bromine and then determined colorimetrically with
    ammonium molybdate is suggested. The method is sensitive to 0.01 ppm
    of phosphine.


    Phosphine aerates rapidly from treated foodstuffs and a residue of 0.1
    ppm in a raw cereal would yield a residue in bread or other food ready
    for consumption which is at or below the level of detection by current
    methods of analysis (i.e. about 0.01 ppm). Therefore, there is no
    necessity for an acceptable daily intake figure. For cereals in
    international trade, a tolerance of 0.1 ppm expressed as PH3 is

    Data exist for the residues likely to result after the treatment of
    certain other foods with phosphine. These include some processed
    foods. If there should be a need for tolerances for foods other than
    cereals therefore the data in respect to each should be reviewed at
    subsequent meetings with a view to determining the residue limits in
    the foods acceptable to international commerce.

    Further work

    Further information is desirable on the levels of Phosphine occurring
    in foodstuffs which have been treated in the course of commerce.


    Anon. (1964) Threshold limit values for 1964, Arch. environm.
    Hlth, 9, 545

    Flury, F. & Zernik, F. (1931) Schädliche Gase, Berlin, Springer

    Harger, R. N. & Spolyar, L. W. (1958) Arch. industr. Hlth, 18, 497

    Johnson, H. D. & Voss, E. (1952) J. Amer. pharm. Ass., 41, 468

    Laue, V. G. (1954) Nachrichtenblatt für den deutschen
    Pflanzenschutzdienst., 8, 13

    Neubert, D. & Hoffmeister, I. (1960) Arch. exp. Path. u. Pharmak.,
    239, 219

    Schulemann (1953) Unpublished report from Degesch, Frankfurt-am-Main.


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

    Cogburn, R. E. & Tilton, E. W. (1963) Studies of phosphine as a
    fumigant for sacked rice under gas-tight tarpaulins. J. of Econ.
    Entom., 56, pp. 706-708

    Degesch. (1965) Deutsche Gesellschaft für Schädlingsbekämpfung,
    Frankfurt-am-Main, Report on Phostoxin

    Diemair, W. (1954) "Bericht über die Unterschung von mit Phostoxin
    begasten Getreide." Thesis University of Frankfurt-am-Main

    Feuersenger, M. (1960) Über die Bestimmung von
    Schädlingsbekämpfungsmitteln in Lebensmitteln. Bundesgesundheitsblatt
    (10) pp. 149-152

    Heseltine, H. & Thompson, B. H. (1957) The use of aluminium phosphide
    tablets for the fumigation of grain. Milling 28: XII

    Lindgren, D. L., Vincent, L. E. & Strong, R. G. (1958) Studies on
    hydrogen phosphide as a fumigant. J. of Econ. Entom., 51, PP.

    McGregor, H. E. (1961) Evaluation of phosphine gas as a fumigant. The
    Northwestern Miller 265, (13)

    Phyto-pharmacy Committee (Netherlands). (1966) Residues of
    insecticides in cereals, imported in the Netherlands 1964/65. Second
    report, Jan. 1966

    Strong, R. G. & Lindgren, D. L. (1960) Germination of cereal, sorghum,
    and small legume seeds after fumigation with hydrogen phosphide. J. of
    Econ. Entom., 53, (1) pp. 1-4

    White, W. E. & Bushey, A. H. (1949) Aluminium phosphide preparation
    and composition. J. Am. Chem. Soc., 66: 1666

    See Also:
       Toxicological Abbreviations
       Hydrogen phosphide (FAO/PL:1967/M/11/1)
       Hydrogen Phosphide (FAO/PL:1969/M/17/1)
       Hydrogen phosphide (WHO Pesticide Residues Series 1)