FAO, PL:CP/15 WHO/Food Add./67.32 EVALUATION OF SOME PESTICIDE RESIDUES IN FOOD 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 METHYL BROMIDE IDENTITY Synonym Bromomethane Formula CH3Br BIOLOGICAL DATA AND TOXICOLOGICAL EVALUATION Biochemical aspects After absorption, methyl bromide appears to be broken down by the mammalian body, at least in part, for the level of non-volatile bromide in the blood and tissues rises significantly. There is also some evidence that volatile bromide, presumably unchanged methyl bromide, is stored in tissues which are rich in lipoid material. It is doubtful, however, whether these findings are relevant to the consideration of the residues to be found in foodstuffs fumigated with methyl bromide, because in this process as commercially practised no unchanged methyl bromide persists (von Oettingen, 1946). Acute toxicity For rabbits the minimum acute lethal dose of methyl bromide has been estimated at 60-65 mg per kg body-weight, when given by stomach-tube as a solution in olive oil (Dudley et al, 1940). 100 mg/kg of methyl bromide given by stomach-tube as a solution in olive oil proved to be fatal to rats in five to seven hours (Miller & Haggard, 1943). Short-term studies with fumigated foodstuff Rat. When an unspecified number of rats was fed on a diet fumigated with methyl bromide so as to give a residue in the diet equivalent to 5760 ppm, calculated as bromide, the animals developed diarrhoea after three weeks and, over eight weeks in all, their weight gain was slight, their general condition was poor and reproduction ceased (Dudley et al., 1940). In a further experiment extending over 16 weeks in which, again, the number of animals was not disclosed, a residue equivalent to 1304 ppm bromide in the diet gave rise to increased sleepiness, reduced activity. Increased death-rate, decreased weight gain and cessation of activity. Return to a normal diet then led to complete restoration to health (Dudley et al., 1940). A third experiment was carried out with groups each of 36 young white rats, fed on a methyl bromide fumigated diet for 20 weeks. In those receiving the diet in which the residue was equivalent to 5760 ppm bromide adverse effects were observed - partial limb paralysis, scaly tails, a form of xerophthalmia, loss of hair, reduced food intake, inactivity, impaired reproduction and increased mortality. By contrast, those animals on a diet in which the residue was equivalent to 206 and 223 ppm bromide remained apparently healthy, although their weight gain was slightly reduced. Finally, where the diet was a mixed one containing fresh vegetables, cheese, peanuts, and dried fruits, in addition to the rat pellets, all fumigated with methyl bromide at a concentration of 3 lb per 1000 ft3 (48 g/m3) so that the residue was equivalent to a maximum of 240 ppm calculated as bromide, no deleterious effects were seen. In all the experiments there was no significant histopathology (Dudley et al., 1940). Two groups, each of 25 males and 32 females, were fed for one year on a modified Sherman diet, previously fumigated with methyl bromide at the rate of 2 lb and 6 lb respectively per 1000 ft3 (16 g to 48 g/m3) and having an average bromide content of 262 ppm and 637 ppm. A group of 10 male and 15 female rats was fed the same basic diet unfumigated but with the addition of 0.1 per cent (i.e., 1000 ppm) sodium bromide. The control group received the unmodified diet. At the end of 12 months none of the animals showed any evidence of adverse effect in growth rate, organ weights and results of haematological and histological examination (Spencer et al., 1944). Rabbit. Groups, each of 12 rabbits, were fed for one year on diets which had been fumigated with methyl bromide for 24 hours. When the residue was equivalent to 3254 ppm bromide the animals developed a progressive paralysis and urinary retention and all died within two weeks. In the others, for which the residue was equivalent to 67 and 75 pm bromide, there were no abnormalities, apart from a slight reduction in weight gain and some polydypsia and polyuria. Post mortem, bronchopneumonia was common in the high dose group and changes were found in the brain (Dudley et al., 1940). Dog. Twenty-two beagles of both sexes, in groups of four to six animals, were fed for one year on methyl bromide fumigated diets. The residues of 1389, 2975 and 6097 ppm led to a bromide intake of approximately 35, 75 and 150 mg per kg body-weight daily. Another group of dogs was given sodium bromide in the diet at the rate of 100 mg per kg body-weight daily of bromide. Lethargy was seen only in those animals on the high residue intake and there was occasional salivation and diarrhoea both in this group and that on sodium bromide. Otherwise the animals remained substantially healthy and, on post mortem, no significant changes were found (Rosenblum et al., 1960). Long-term studies No long-term studies are available. Comments No work has been done on the long-term oral toxicity of methyl bromide as such. However, it is probable that by far the major part, if not all, of the residue which persists in foodstuffs fumigated with methyl bromide in accordance with ordinary commercial practice is in the form of inorganic bromide. If this is so, the safety of treated products could be assessed simply on the basis of their bromide content. The question still remains whether the small interaction that takes place between the fumigant and the food constituents could lead to a significant decrease of nutritional value or to the formation of toxic compounds. The answer to this should be provided by the feeding studies with animals given a diet which had previously been fumigated. These experiments have been short term and covered three species of animals. From these it is clear that diets fumigated with methyl bromide at the usual rates adopted commercially had no deleterious effects on any of the animals. TOXICOLOGICAL EVALUATION Since nothing is known about the long-term oral toxicity of unchanged methyl bromide no acceptable daily intake can be assigned to it as a residue. To judge by the work on cereal products the interaction of the compound with the food is unlikely to have hazardous consequences. The minimum pharmacologically effective dosage in the human adult has been generally stated to be about 900 mg of KBr, equivalent to 600 mg of bromide ion, daily. Assuming an adult weight of 60 kg this dosage in man is about 10 mg/kg body-weight/day. In the light of available toxicological information obtained from the extensive therapeutic use in man, an acceptable daily intake for man of inorganic bromide from all food sources can be estimated. Estimate of acceptable daily intake for man of inorganic bromide 0-1.0 mg/kg body weight. Further work required for unchanged methyl bromide Chemical nature and amount of the residue in foods other than cereals. Biochemical studies on the changes produced by methyl bromide in food. Results of the above work should be made available not later than three years after the publication of this report, when a re-evaluation of this compound will be made. Depending on the results of the above two studies, additional work such as biochemical studies in animals, reproduction studies and long-term toxicity studies may be required. RESIDUES IN FOOD AND THEIR EVALUATION Use pattern (a) Pre-harvest treatments Methyl bromide is very phytotoxic to growing plants, thus limiting its pre-harvest uses. Such uses were reviewed by Page & Lubatti (1963). It is applied to soils before planting, at low doses, to some seeds and plants for quarantine purposes. These uses do not give rise to significant bromide residues in foods. (b) Post-harvest treatments Methyl bromide is used against storage pests on cereals in many countries. Treatment is carried out in various kinds of enclosures, including chambers at atmospheric or reduced pressures, in warehouses, in box cars and in barges. These are sometimes temporarily adapted for the purpose. A few elevators are equipped for forced circulation of the fumigant. For economic reasons, treatments are normally reserved for specific shipments requiring remedial measures and are not carried out as a matter of routine. Much of the methyl bromide used in commerce contains an indicator substance (e.g. chloropicrin at two per cent) which gives a readily perceptible warning of leakage from fumigant containers or from stores being treated. It is also occasionally used in admixture with "liquid fumigants". For example, a mixture mainly containing carbon tetrachloride has high powers of penetration down into standing grain and is sometimes applied at the top of deep bins of standing grain. Mixtures with ethylene dibromide are also used in a few countries, (Majumder, Muthu & Narasinham, 1963) for the fumigation of stocks of grain in bags. Some proprietary preparations contain three or more other components (e.g. ethylene dichloride, ethylene dibromide, carbon tetrachloride, carbon disulfide). Methyl bromide is also used occasionally on processed cereals such as flour and milling by-products. It is used on a wide range of stored products including dried fruits, pulses, nuts, oilseeds, animal feed and other dry foodstuffs; also against insects in clothing, furniture and timber. Tolerances There are no tolerances for unchanged methyl bromide. For inorganic bromide derived from fumigation the figures in Brazil, Germany, India, the Netherlands, Canada and USA for various cereal are 50 ppm and in Czechoslovakia 20 ppm; in New Zealand there is a tolerance of 20 ppm in any food. Gibich & Petersen (1963) have determined inorganic bromide residues in various mill fractions of fumigated and unfumigated wheat. Even with unfumigated wheat great differences were observed in the amounts of bromide located in different parts of the grain. The rejected fractions (screenings and scourers) ran at 50-100 ppm approximately whether fumigated or not, whereas flour and feed fractions gave Br residues up to four times higher in treated, compared with untreated samples. The type of wheat itself to some extent determines the amount of Br found in certain fractions and there is some correlation between bromide level and fat and protein contents. Some results obtained are summarized in Table II. TABLE II. TOTAL BROMIDE RESIDUE IN MILL FRACTIONS FROM TREATED WHEAT (PPM) Mill fraction Hard red winter wheat Hard red spring wheat Clean wheat 11.7 29.7 38.6 18.2 39.1 A grade flour 11.0 18.6 22.9 19.1 21.3 X grade flour 24.3 28.0 30.9 35.8 31.8 Y grade flour 21.0 39.5 36.6 38.3 36.9 Head shorts 10.3 60.8 79.8 22.9 96.0 Tall shorts 17.6 60.1 75.2 31.5 101.2 Bran 10.0 42.6 57.1 19.1 56.1 Germ 16.4 109.4 113.2 18.0 212.8 Dirty wheat 8.9 25.3 35.1 17.8 43.1 Screenings 51.9 55.1 60.8 17.8 71.5 Scourers 72.8 82.6 115.8 62.6 119.9 An examination of 227 grain shipments to the Netherlands from all parts of the world in the period May 1964 to September 1965, showed inorganic bromide residues to be present in only 14 of these. The measurement of residues of unchanged fumigants are still being developed but preliminary observations on the 227 shipments above showed that residues of unchanged methyl bromide, if any, did not exceed 0.1 ppm. Residues resulting from supervised trials During the exposure period some of the fumigant is sorbed1 by the cereals or cereal products. The amount increases with the dosage used under given circumstances and a higher moisture content usually results in a higher residue. For example, some wheat of nine per cent moisture content exposed at 32 g/m3 for 24 hours, gave an immediate total bromide figure of 30 ppm whereas one at 15 per cent moisture under the same experimental conditions gave 99 ppm (Lindgren, Gunther & Vincent, 1962). As shown by Lubatti & Harrison (1944), Shrader, Beshgetoor & Stenger (1942) and Winteringham (1955) immediately after the termination of the exposure period the residue consists partly of unchanged methyl bromide and partly of a fixed residue resulting from some kind of reaction with constituents of the food. The unchanged methyl bromide disappears quite rapidly leaving a fixed residue which does not decrease on further airing. This fixed residue behaves as inorganic bromide. As examples of the rate of disappearance of unchanged methyl bromide, the above-mentioned wheat, which had contained a total of 30 ppm immediately after treatment contained 19 ppm six hours later and 17 ppm after eight days and that which had contained 99 ppm immediately gave 78 ppm and 77 ppm after these same intervals of time. These losses are due to disappearance of unchanged methyl bromide. Flour has been found to take up rather more than wheat when they are exposed under identical conditions. Winteringham (1955) showed that the fixation of the methyl bromide is due mainly to reaction with the protein fraction mainly by methylation of nitrogen and sulfur-containing groups with the formation of methylated histidines, dimethyl sulfonium derivatives and lesser amounts of methoxy and thiomethoxy derivatives. These reactions have not been considered to be sufficient to reduce the nutritive value of the products. Figures for residues after commercial, or simulated commercial treatments of wheat and flour vary widely. In one test with cornflour, Wagner (personal communication) gives 75 ppm. In another case a figure as high as 150 ppm for total bromides was reported in flour immediately after fumigation and before airing had taken place. For whole wheat, residues are rather lower than when the processed grain such as flour is exposed. Wheat of 12 per cent moisture content exposed under commercial conditions gave an initial total bromide residue of 35.5 ppm which fell to 14 ppm in 24 hours (Pest Infestation Laboratory, 1947). Wheat of 15 per cent moisture content however had a residue of 78 ppm after 24 hours, following a fumigation under identical conditions. These variations are probably due to the wide 1 This term is used so as to include all the gas taken up by the exposed solid irrespective of the particular mechanism or mechanisms, such as solution, surface retention or chemical combination, which may be involved in any given case. range of conditions of exposure which occur in practice, including dosages, period of exposure, tightness of the enclosure, moisture content of the cereals and cereal products treated and whether or not they are turned or aired before sampling. Burns-Brown et al. (1955) reported residues of about 50 ppm, inorganic bromide in flour after treatments corresponding to normal commercial practice. The bromide content of commercial flour which has not been treated with a fumigant of any kind has been reported to fall between 2.4 and 7.7 ppm (FAO/WHO, 1964) Getzendaner (1966a) measured bromide residues in cocoa beans and processing fractions resulting from the experimental fumigation of beans with methyl bromide. Under the conditions used (five fumigations with 1-1/2 lb methyl bromide per 100 cu. ft for 24 hours; 7-1/2 lb in one fumigation, or 4-1/2 lb for 24 hours followed by 4-1/2 lb for 12 hours), residues of less than 50 ppm bromide were found after 24 hours aeration. The shells of fumigated beans contained between four and six times the amount found in a whole bean. Cocoa residues were about the same as those found in the whole beans, but lower residues were found in corresponding butter and nib fractions. Getzandaner & Richardson (1966) have measured bromide residues in fruit and vegetables experimentally fumigated with methyl bromide. Treatment at atmospheric pressure in general gave residues of less than 25 ppm of bromide. Yams, however, approached 30 ppm and sweet corn and peas up to 40 ppm bromide. Typical results for other produce were: cherries 8 ppm; peaches 3 ppm; carrots 20 ppm; oranges, grapefruit 12 ppm; cucumber 15 ppm; apples 3 ppm; cabbage 20 ppm bromide. Garlic subject to vacuum fumigation in commercial chambers had residues of 2 to 11 ppm and cipollini bulbs up to 48 ppm bromide. Getzandaner (1965) has also shown that poultry meat and eggs from hens fed diets containing up to 400 ppm bromide residues contain at equilibrium no more bromide residue than the diet. Bär (1964) found that whilst cereals, fruit and vegetables retained only small residues after treatment, flour and oily goods retained much higher levels even after 48 hours aeration. Maximum levels (for inorganic bromide) cited by the German Federal Office of Health from rat feeding studies reported by Bär are: cereals and citrus fruit skin 50 ppm; almonds and other nuts (kernels) 40 ppm; citrus pulp 25 ppm; cocoa beans, dried fruit 10 ppm. The feeding of fumigated cereals to cattle may result in bromide residues in milk. Lynn (1963) found 10-20 ppm in milk from cows fed a diet containing 43 ppm bromide. Residues in food moving in commerce Duggan, Barry & Johnson (1966) reported total bromide levels of up to 200 ppm in various defined food groups in total diet studies; results are summarized in Table I. Heywood (1966) pointed out that not all of this bromide could be attributed to fumigants since part, at least, occurred naturally in food. TABLE I. BROMIDE RESIDUES IN TOTAL DIET STUDIES Foods Bromide range ppm No. of samples (out of 18) Dairy produce 1.1 to 31.7 17 Meat, fish 2.3 to 35.5 16 Grain 4.4 to 111.0 17 Potatoes 1.5 to 38.0 15 Leafy vegetables 1.1 to 16.3 16 Legumes 0.9 to 17.9 14 Root vegetables 2.6 to 22.1 14 Salad fruit 1.7 to 18.9 15 Fruit 0.7 to 31.4 12 Oils, fats 1.1 to 261.0 16 Sugar, etc. 0.7 to 55.1 18 Beverages 0.9 to 17.0 10 Fate of residues (a) In plants and animals There is a fairly extensive literature on the activity and excretion of inorganic bromides in animals and man. As indicated by Heywood (1966), furthermore, small amounts of bromide occur naturally on a fairly wide range of plant products. Residues of "apparent organobromine compounds" reported by Gunther & Spenger (1966) were said to be due to the extraction of inorganic bromide by organic solvents in the presence of lecithin-type complexing agents present in vegetable tissues. The results obtained, indicated in Table II, probably reflect naturally occurring bromide in the various plants. TABLE II. APPARENT ORGANOBROMINE RESIDUES IN PLANT PARTS Plant Plant part Bromine ppm Atriplex lentiformis Leaves and stems 4.4 4.9 Schinus Molla Tops 1.1 Suaeda sp. Whole plants 0.3 Beets Tops 0.15 Broccoli Heads 0.13 Chard Foliage 0.2 Corn, sweet Leaves 0.15 Cucumber Seeds 9.9 Barley Whole plants 0.34 0.26 Lima beans Whole plants 0.2 Onions Whole plants 0.18 0.27 Peppers Whole plants 0.18 Radishes Whole plants 0.1 Zucchini Fruits 0.13 (b) In storage and processing Methyl bromide disappears rapidly from whole wheat and cannot be detected after three or four days of airing. The combined bromide does not disappear to a significant extent during airing. When fumigated wheat has been milled the residues found in the various milling fractions, present at the stage as inorganic bromide, have been found to vary: the residues in flour and other fractions for human consumption, however, have always been appreciably lower than those in the original wheat. For example, on one occasion wheat with 14 ppm bromide gave flour of 5 ppm but the bran contained 13 ppm (Pest Infestation Laboratory, 1947). Wagner (personal communication) quotes a wheat of 26.8 ppm which yielded a flour of 12.2 ppm but the bromide residues in the animal feed fractions had slightly increased. Methods of residue analysis Berck (1965) has published details of a gas chromatographic method for the detection and measurement of some 34 fumigant vapours, including methyl bromide. The application of this technique to the determination of residues of unchanged methyl bromide in fumigated foods is most desirable. The method of Napes & Shrader (1957), based on the measurement of inorganic bromide, is in the meantime suggested as suitable for measuring residues of total bromide in cereals after fumigation. Working details are set out in Appendix A(4) of the (Extract) Report of the Second Session of the FAO Working Party on Pesticide Residues (PL/1965/12). The limit of detection is about 1 ppm. The Joint FAO/WHO Expert Committee on Food Additives, when considering the presence of bromide in bread due to the addition of bromate conditioner to flour (FAO/WHO, 1964) gave estimates of acceptable levels of treatment for flour to be consumed by man as: Unconditional 0-20 ppm Conditional (for special purposes) 20-75 ppm The recommendation of 50 ppm in cereals and flour resulting from fumigation, is in accordance with this estimate because cereals and cereal products are treated with the fumigant to deal with specific outbreaks and not as a routine, during milling or other manufacture, as are flour conditioners. RECOMMENDATION FOR TOLERANCES On the basis of an acceptable dally intake of 1 mg/kg of inorganic bromide, a tolerance of 50 ppm for inorganic bromide residues in cereals and flour resulting from the use of methyl bromide and other fumigants can be recommended. This recommendation is also consistent with tolerances for dried eggs, processed herbs and spices at 400 ppm; various fresh fruits at 200 ppm; citrus at 230 ppm; raisins, dates at 100 ppm and various other fruits including certain dried fruits, at from 50 ppm to 20 ppm, which are residues which have been found after responsible usage of the fumigant and which are as follows: Dried eggs, spices, herbs 400 Cereals 50 Dried figs 250 Avocados 75 Dried raisins, dates 100 Dried peaches 50 Dried prunes 20 Other dried fruits 30 Citrus, strawberries 30 Other fresh fruit 20 Since no acceptable daily intake has been established for the unchanged compound and since there appears to be no requirement for such a tolerance in commercial practice, no tolerance is recommended for residues of unchanged methyl bromide. Further work or information The measurement of residues of bromide, and of unchanged methyl bromide (if any) resulting from the use of methyl bromide on raw wheat, flour and other food items in commercial practice is desirable. There would be particular interest in information on the retention of unchanged methyl bromide in foods with a relatively high oil or fat content. Further information on residues resulting from the use of mixed fumigants is also desirable. The Working Party considers that a sensitive multidetection method for residues of unchanged fumigants (including methyl bromide) in treated foods is now possible and the development of such a method would be a valuable advance. REFERENCES PERTINENT TO BIOLOGICAL DATA Dudley, H. C., Miller, J. W., Neal, P. A. & Sayer, R. R. (1940) Publ. Hlth Rep., 55, 2251 Miller, D. P. & Haggard, H. W. (1943) J. industr. Hyg. Toxicol., 25, 423 von Oettingen, W. F. (1946) Nat. Inst. Hlth Bull., 185 Rosenblum, I., Stein, A. A. & Eisinger, G. (1960) Arch. environ. Hlth, 1, 316 Spencer, H. C., Rowe, V. K., Adamo, C. M. & Irish, D. D. (1944) Food Res., 9, 11 REFERENCES PERTINENT TO AGRICULTURAL DATA Bär, F., (1964) Methylbromide zur Schädlingsbekämpfung Bundesgesundheitsblatt, 7: 113 Berck, B., (1965) Determination of fumigant gases by gas chromatography J. Agric. Food Chem. 13 (4): 373-377 Burns-Brown, W., Coppock, J. B. M., Edwards, G. H., Greer, E. K., Hay, J. G. & Heseltine, H. K. (1955) The fumigation of flour with methyl bromide. Chem. Ind., March 19, 1955: 324-5 Duggan, R. E., Barry, H. C. & Johnson, L. Y. (1966) Pesticide residues in total-diet samples Science, 151 (3706): 101-104 FAO/WHO (1964) Specifications for the identity and purity of food additives and their toxicological evaluation: emulsifiers, stabilizers, bleaching and maturing agents. FAO Nutr. Meetings Rep. Ser. 35: 167 FAO/WHO (1965) Evaluation of the toxicity of pesticide residues in food. Rome FAO Meeting Report No. PL/1965/10/2, 71 p. Getzendaner, M. E. (1965) Residues in milled wheat products resulting from spot fumigation of milk machinery with halogenated liquid fumigants. J. Agric. Food Chem., 13: 455-458 Getzendaner, M. E. (1966a) Bromide residues from methyl bromide fumigation of cocoa beans and processed fractions from fumigated beans. J. Agric. Food Chem., 14: 56-58 Getzendaner, M. E. & Richardson, H. H. (1966b) Bromide residues from methyl-bromide fumigation of fruits and vegetables subjected to quarantine schedules J. Agric. Food Chem., 14: 59-62 Gibich, J. & Pederson, J. R. (1963) Bromide levels in mill fractions of unfumigated and fumigated wheat. Cereal Science Today, 8: 345-354 Gunther, F. S. & Spenger, R. E. (1966) Apparent organobromide compounds in higher plants by neutron activation analysis. Bull. Environ. Contam. Toxicol., 1: 121 Heywood, B. J. (1966) Pesticide residues in total diet samples: bromine content. Science, 152 (5727): 1406 Lindgren, D. L., Gunther, F. A. & Vincent, L. E. (1962) Bromine residues in wheat and milled wheat fractions fumigated with methyl bromide. J. Econ. Ent., 55: 773-6 Lubatti, O. F. & Harrison, A. (1944) Determination of fumigants. XVII. Comparison of the sorption of hydrogen cyanide, ethylene oxide, trichloro-acetonitrile and methyl bromide by wheat. J. Soc. Chem. Ind, 63: 353-9 Lynn, G. E., Shrader, S. A., Hammer, O. H. & Lassiter, C. A. (1963) Occurrence of bromide in the milk of cows fed sodium bromide and grain fumigated with methyl bromide. J. Agric. Food Chem., 11: 87-91 Majumder, S. K., Muthu, M. & Narasinham, K. S. (1963) Behaviour of ethylene dibromide methyl bromide and their mixtures. I: in columns of grains and milled materials. Food Technol., 17; 106-111 Mapes, D. A. & Shrader, S. A. (1957) Determination of total and inorganic bromide residues in fumigated products. J. Ass. Offic. Agr. Chem., 40: 189-96 Page, A. B. P. & Lubatti, O. F. (1963) Fumigation of insects. Annu. Rev. Ent., 8: 239-64 Pest Infestation Laboratory. (1947) The effect on the milling and baking quality of wheat after fumigation with methyl bromide. Slough, Bucks. Pest Infestation Res. Rep. 11 (unpublished document) Shrader, S. A., Beshgetoor, A. W. & Stenger, V. A. (1942) Determination of total inorganic bromide on food fumigated with methyl bromide. Ind. Eng. Chem. Anal. Ed. 14: 1-4 Winteringham, F. P. W. (1955) The fate of labelled insecticide residues in food products. IV. The possible toxicological and nutritional significance of fumigating wheat with methyl bromide. J. Sci. Food Agr., 6: 269-74
See Also: Toxicological Abbreviations Methyl Bromide (EHC 166, 1995) Methyl bromide (ICSC) Methyl bromide (PIM 340) Methyl bromide (FAO Meeting Report PL/1965/10/2) Methyl bromide (FAO/PL:1967/M/11/1) Methyl bromide (FAO/PL:1968/M/9/1) Methyl bromide (WHO Pesticide Residues Series 1) Methyl Bromide (IARC Summary & Evaluation, Volume 71, 1999)