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
ETHYLENE DIBROMIDE
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 the results of
additional experimental work have been reported. This new work is
summarized and discussed in the following monograph addendum.
EVALUATION FOR TOLERANCES
USE PATTERN
Other uses
In addition to the previously described uses, ethylene dibromide may
be used as a soil fumigant for nematode control.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Beckman et al. (1967) have reviewed the inorganic content of
foodstuffs due to soil treatment with fumigants. Since organically
bound bromine is not taken up by plants from the soil, they authors
interpret any bromine increase in the plants as being due to the
bromide fumigant used. In general, the leafy portions of plants
contain the most bromide but the edible portions of certain other
crops also take up significant amounts of bromides as the result of
soil fumigation. Results for ethylene dibromide (and for
1,2-dibromo-3-chloropropane) are given in Tables I and II, which
relate to the range of total inorganic bromide residues found in crops
grown on triplicate (mainly) plots treated at Davis, California in
1964 and 1965. Most crops were harvested about 100 days after soil
treatment; but intervals ranged from 55 days (strawberries) to 10
years (walnuts). Residues occurred notably in beet tops, string beans
and spinach.
TABLE I
Total Inorganic Bromide in Crops Grown on Treated Soils, 1964
Recovery Time (days Bromide (ppm)
fortified treatment Check
crop to harvest) sample DBCP EDB
Cottonseed 70.5 185 0.6 NT 0.4- 2.8
Cottonseed 70.5 206 0.8 1.0- 2.2 NT
Cottonseed 92 150 3.2 5.2- 7.6 NT
TABLE I (cont'd)
Total Inorganic Bromide in Crops Grown on Treated Soils, 1964
Recovery Time (days Bromide (ppm)
fortified treatment Check
crop to harvest) sample DBCP EDB
Green beans 88 73 2.4 3.4-13.0 4.0-24.0
Green beans 76 87 0.4 1.1- 1.6 8.0- 2.5
Green beans 70 103 0.1 0.5- 2.8 0.5- 2.4
Baby lima beans 74.4 103 0.1 4.0- 8.2 1.0- 8.5
Beans, black eye 70 96 0.3 6.0- 9.9 3.9- 6.3
Okra 48.5 0.5 0.4- 2.9 3.5-13.0
Turnip 70 72 2.4 3.4-13.0 4.0-24.0
Turnip greens 7 51 1.4 22.0-47.0 28.0-63.0
Spinach 82 72 4.6 25.0-52.0 20.0-73.0
Radish 110 49 2.0 12.0-26.0 15.0-33.0
Table beet tops 70 72 6.0 54.0-94.0 52.0-72.0
Cherries 70 180 0.6 0.7 NT
TABLE II
Total Inorganic, Bromide in Crops Grown on Treated Soils, 1965
Fortified Time (days Bromide residue (ppm)
Crop std. treatment Check
(% recovery) to harvest) sample DBCP EDB
Beans 100 78 0.3 3.1- 7.4 11.0-22.0
Beans 100 88 0.3 5.5-14.0 8.0-14.0
Beans 95 98 * 1.8- 4.6 7.4-15.0
Beans, dry black eye 95 147 0.3 2.4- 5.5 3.2- 4.0
TABLE II (cont'd)
Total Inorganic, Bromide in Crops Grown on Treated Soils, 1965
Fortified Time (days Bromide residue (ppm)
Crop std. treatment Check
(% recovery) to harvest) sample DBCP EDB
Baby lima beans 90 155 * 0.3- 1.1 0.6- 1.4
Sweet corn 70 95 0.4 2.0- 3.9 1.1- 4.4
Okra 92 78-89 2.0 8.0-20.0 3.7- 8.6
Hop-flower 94 91 * 16.0 NT
Prunes 80 173 0.3 0.7- 0.9 NT
Tokay grape 94 3 yr. 0.9 0.8- 1.4 NT
T.S. grape 92 270 1.2 0.3- 2.3 NT
T.S. grape 92 1 yr. 0.9 1.1 NT
T.S. grape 98 4.5 yr. 1.2 0.3- 0.7 NT
Sugar beet tops 89 147 17.8 43.0-78.0 66.0-224.0
Sugar beet tops 80 322 9.5 18.0-38.0 27.0- 92.0
Sugar beet roots 80 322 3.9 7.0-21.0 33.0- 83.0
Walnuts 80 510 * 1.8-10.0 NT
Walnuts 80 10 yr. * 0.2- 1.2 NT
Cottonseed 85 183 * 1.6- 6.4 NT
* less than 0.2 NT = no treatment
FATE OF RESIDUES
In storage and processing
The nature of terminal residues arising from the use of ethylene
dibromide and other fumigants was reviewed by the IUPAC Commission on
Terminal Residues in 1967. The Commission stressed the need for a
method of analysis sensitive to 0.1 ppm of unchanged ethylene
dibromide in order further to evaluate the levels of this in food as
consumed, especially insofar as this might indicate that no residues
other than (a) inorganic bromide and (b) unchanged ethylene dibromide
might be present as the result of ethylene dibromide treatment.
The following note is adapted from a memorandum on terminal residues
arising from the use of fumigants, prepared for IUPAC meetings in
August (IUPAC, 1967a).
"The pertinent question which needs to be resolved is whether ethylene
dibromide leaves the grain completely upon a certain period of
aeration (this may be highly variable and not dependable without
analysis) or whether normal food processing and cooking will
completely aerate ethylene dibromide or hydrolyze it. The nature and
the amount of bromide residue occurring as a result of fumigation with
liquid grain fumigants containing ethylene dibromide was determined by
the use of radioactive bromide-82 (Anon. 1963). Ethylene dibromide was
completely absorbed by wheat grain. About 50 per cent, presumably
ethylene dibromide, was given off by heat treatment at 110-120°C for
one hour. The remaining bromide non-volatile compounds are only
slightly extractable with organic solvents by Soxhlet extraction for
ten hours and are water soluble, probably a mixture of sodium and
potassium bromide. After five days contact with the grain, 50 per cent
of the original ethylene dibromide was changed to inorganic bromide.
The remaining 50 per cent can be volatilized in 59 hours in open air.
Contrary to the use of uncooked grain for domestic animals and birds,
man eats very little grain that is not processed in some way. Ethylene
dibromide is lost from treated grain via turning, aeration, tempering,
milling, etc. to a small percentage of the original level before
cooking. Stenger and Mapes (1957) showed that when wheat flour
containing 8 ppm ethylene dibromide was baked into broad rolls, the
ethylene dibromide itself did not survive the baking process. The
sensitivity of the analytical method used was 1 ppm of ethylene
dibromide. Munsey, et al (1957) in a baking study, added 15 and 20 ppm
of ethylene dibromide (10 × the levels resulting from usual
fumigations) to the flour and bread bases, prior to baking one-pound
loaves of bread. The analyses of the baked bread showed that there was
no ethylene dibromide per se remaining after baking within the
analytical limits of the method (1 ppm). Rolled oats treated to attain
about 10 times the expected residue level of ethylene dibromide, quick
cooked for one minute, reduced ethylene dibromide 51 per cent from
24.4 to 12 ppm. Considering normal processing procedure for producing
rolled oats, it seems very unlikely that any measurable amount would
be left in cooked commercial rolled oats."
METHODS OF RESIDUE ANALYSIS
In reviewing methods of analysis for unchanged residues arising from
the use of ethylene dibromide, the IUPAC Commission on Residue
Analysis (IUPAC, 1967b) also drew attention to the possibility that
small residues of modified (and possibly more toxic) compounds might
not be detected by such methods. The Commission recognised the
desirability of studies on the recovery of ethylene dibromide from
treated produce, however (using chromatographic techniques for the
unchanged fumigant and by established methods for the increase in
inorganic bromide arising from the fumigation). In its review the
Commission made special reference to the progress of work on
multidetection systems for unchanged residues from mixed fumigants,
including mixtures containing ethylene dibromide. Heuser and Scudamore
(1967b) have shown that cold extraction with 5:1 v/v acetone-water is
far more effective than the various steam distillation methods
described earlier for the recovery of residues of unchanged ethylene
dibromide and other fumigants from flour. Residues have been extracted
by this method from flour and from ground whole wheat by shaking with
the solvent in a stoppered vessel. Aliquots of the clear supernatant
liquor were injected into a gas chromatograph using a 50 per cent w/w
polypropylene glycol on a chromosorb W column and flame-ionization
detector. A specially designed injection unit was developed for this
purpose. Recoveries or these substances were from 95 - 100 per cent,
checked by independent vapour-phase application and subsequent
aeration techniques, with chemical analysis of the vapours removed.
Carbon disulphide is expected to yield a similar result and it is
highly probable that residual amounts of other fumigants such as
carbon tetrachloride, ethylene dichloride and acrylonitrile are
extracted with equal efficiency by this solvent. However, the
proximity of their boiling points to that of acetone makes the gas
chromatographic separation of minute amounts from the solvent peak
difficult. Present investigations are concerned with the use of the
electron-capture detector for these and other compounds since it is
relatively much less sensitive to acetone; and with the search for a
suitably effective higher-boiling solvent which would widen the
application of the flame ionization detector. Wit and Grevenstuk
(1967) at Utrecht are working on the determination of unchanged
ethylene dibromide and other fumigant residues in wheat, using the
distillation-extraction method followed by gas-liquid chromatographic
analysis with electron capture detection. Bielorai and Alumot (1966)
have continued residue determinations on whole cereals using a similar
technique but the proprietary fumigant mixtures used in this work did
not include ethylene dibromide.
NATIONAL TOLERANCES
While there are no tolerances for residues of unchanged ethylene
dibromide, tolerances for inorganic bromide resulting from the use of
ethylene dibromide for fumigation (in conjunction with methyl bromide)
have been published in the U.S. Federal Register (1966) as follows :
Dried egg, processed herbs, apiece 400 ppm
Barley, corn, milo (sorghum) rice,
rye, wheat flours 125 ppm
RECOMMENDATIONS FOR TOLERANCES
No change from previous recommendation (FAO/WHO, 1967).
Previous considerations have been on the basis of an acceptable daily
intake of 1 mg/kg of inorganic bromide (FAO/WHO, 1967). Tolerances
proposed at the previous meeting (FAO/WHO, 1967) have since bean
considered at the Second Session of the Codex Committee on Pesticide
Residues (September 1967).
The general position may be summarized as follows :
Although the residual ethylene dibromide content of flour and various
milling fractions have been measured in experimental procedures on
numerous occasions, almost all of this work is based on the
measurement of inorganic bromide residues; or the difference between
such residues before and after airing. The general significance of
results obtained in this way was summarized in a previously published
document (FAO/WHO, 1965): ethylene dibromide has poor powers of
penetration, is strongly absorbed by cereals but appears to be mainly
unchanged (i.e. only a small proportion is converted to ionized
bromide), is resistant to dispersion by airing but is largely lost by
volatilization on baking or cooking.
Limited results for commercial shipments of wheat were subsequently
reported (FAO/WHO, 1967): only one shipment in 227 contained unchanged
ethylene dibromide (0.5 ppm). Unchanged ethylene dibromide could not
be detected in 99 cargoes of wheat shipped from all parts of the
world, using a method sensitive to 2 ppm. There appears to be no
corresponding information at all for dry goods such as spices and
dried fruit.
FURTHER WORK
Further work desirable
In addition to that listed in the previous publication (FAO/WHO, 1967)
the application of recently developed methods of extraction (Heuser
and Scudamore, 1967a) and chromatographic analysis to cereals and
flour in commerce is most desirable.
REFERENCES PERTINENT TO EVALUATION FOR TOLERANCES
Anon. (1963) Residues resulting from the fumigation with liquid grain
fumigants containing ethylene dibromide. The Dow Chemical Company,
Midland, Michigan.
Beckman, H., Crosby, G.C., Allen, P.T. and Mourer, C. (1967) The
inorganic bromide content of foodstuffs due to soil treatment with
fumigants. J. Food Sci 32: 138-140
Bielorai, R. and Alumot, E. (1966) Determination of residues of a
fumigant mixture in cereal grain by electron capture gas
chromatography. J. Agr. Food Chem. 14: 622.
Bondi, A. and Alumot, E. (1966) Final Report of Research Conducted
under Grant Authorized by Public Law 480. Effect of Ethylene Dibromide
Fumigated Feed on Animals. USDA, Washington, D.C.
FAO/WHO. (1965) Evaluation of the toxicity of pesticide residues in
food. FAO Meeting Rept. PL/1965/10/1; WHO/Food Add./27.65.
FAO/WHO. (1967) Evaluation of some pesticide residues in food. FAO
PL:CP/15; WHO Food/Add./67.32
Heuser, S.G. and Scudamore, K.A. (1967a) Analyst 92: in press
Heuser, S.G. and Scudamore, K.A. (1967b) Determination of ethylene
chlorohydrin, ethylene dibromide and other volatile fumigant residues
in flour and whole wheat. Chem. Ind. 1557-1560.
IUPAC. (1967a) Commission on Terminal Residues: Proceedings of the
Meeting held in Vienna, Appendix VIII.
IUPAC. (1967b) Commission on Residue Analysis: Proceedings of the
Meeting held in Vienna, Appendix XV.
Munsey, V.E., Mills, P.A. and Klein, A.K. (1957) J. Assoc. Off. Agr.
Chem. 40: 201
Stenger, V.A. and Mapes, D.A. (1957) J. Assoc. Off. Agr. Chem. 40:
196.
U.S. Federal Register. (1966) 1 October.
Wit, S.L. and Grevenstuk, W. (1967) Private communication quoted in
Appendix XV to Proceedings of IUPAC Commissions 1967.
See Also:
Toxicological Abbreviations
Ethylene dibromide (ICSC)
Ethylene dibromide (FAO Meeting Report PL/1965/10/2)
Ethylene dibromide (FAO/PL:CP/15)
Ethylene dibromide (FAO/PL:1968/M/9/1)
Ethylene Dibromide (IARC Summary & Evaluation, Volume 71, 1999)