FAO/PL:1967/M/11/1 WHO/Food Add./68.30 1967 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD THE MONOGRAPHS 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) FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS WORLD HEALTH ORGANIZATION Rome, 1968 HYDROGEN PHOSPHIDE 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 addendum. IDENTITY 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. EVALUATION FOR TOLERANCES USE PATTERN 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. RESIDUES RESULTING FROM SUPERVISED TRIALS 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, 1967). 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)). FATE OF RESIDUES 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). METHODS OF RESIDUE ANALYSIS 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. NATIONAL TOLERANCES 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 RECOMMENDATIONS FOR TOLERANCES Tolerances 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 food. 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 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 limits. More data are also desirable on the phosphine residues in various food moving in commerce and on the amount of phosphine in total diet studies. REFERENCES PERTINENT TO EVALUATION FOR TOLERANCES 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)