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
EDB, ethylene bromide
BIOLOGICAL DATA AND TOXICOLOGICAL EVALUATION
The fate of ethylene dibromide absorbed from the mammalian alimentary
tract has apparently not been determined. After uptake by the
pulmonary route, however, some of the compound is excreted through the
lungs and some of it is changed in the body with the formation of
organic bromides (von Oettingen, 1955).
Animal Route LD50 Reference
Mouse, female Oral 420 Rowe et al., 1952
Rat, male " 146 "
Rat, female " 117 "
Chick " 79 "
Guinea-pig " 110 "
Rabbit, female " 55 "
A 43-year-old woman who took a single dose of ethylene dibromide
amounting to 4.5 ml died 54 hours later after symptoms of vomiting,
diarrhoea and anuria. At autopsy there was massive centro-lobular
necrosis of the liver and proximal tubular damage in the kidney
A total of 19 rats and guinea-pigs was fed ethylene dibromide in oil
or 50 per cent alcohol for about 4 months and there were no abnormal
signs in those receiving about 40-50 mg/kg/day, but no pathological
tests or autopsy examinations appear to have been undertaken (Aman et
Fumigants in 50 per cent aqueous ethanol solution were administered
directly into the crops of adult hens. Individually caged birds were
given respectively 0.5, 1, 2, 4 and 20 mg ethylene dibromide/hen/day
for 8 weeks. An additional group was given 8 mg/hen/day together with
ethylene dichloride and carbon tetrachloride at levels which had no
effect when given alone. At 8 mg/day (with other fumigants) and 20
mg/day both egg production and egg weight were decreased, whilst at 2
and 4 mg/day only egg weight was depressed. At 0.5 and 1.0 mg/day
there were no differences from the controls. Haugh units of quality
and shell thickness were also determined in this study, and the
fumigant had no effect on these parameters (Fuller & Morris, 1962).
In another experiment, groups of 24 pullets were treated for 12 weeks,
rested for 8 weeks, and treated again for 12 weeks. Doses were 0, 0.5,
1, 2, 4 and 8 mg/bird/day. Egg production was depressed at 8 mg/day
only. Egg weight was reported to be significantly decreased at all
levels. However, the decrease at 0.5 and 1 mg/bird/day was very small.
At necropsy, the birds receiving 8 mg/day and showing lowered
productivity were found to have an excessive number of incompletely
developed ovarian follicles, but no abnormalities in liver, brain or
kidney. Effects on egg production and egg weight were comparable among
two groups of hens treated at 7 and 18 months of age respectively
(Fuller & Morris, 1962).
Two-week-old chicks, in groups of 24, were fed for two weeks on a
ration to which ethylene dibromide in ethanol and olive oil had been
added at levels of 20, 40 and 80 ppm. Estimates made from chemical
analyses suggested that these amounts would be reduced by evaporation
and by conversion to inorganic bromide to somewhat less than 10, 20
and 40 ppm by the time the ration was consumed. At 10 and 20 ppm no
change was observed in the chicks over the two weeks, but at 40 ppm
there was retardation of growth rate, even when a correction was made
for food intake (Morris & Fuller, 1963).
Six-month-old pullets in groups of 10 were given ethylene dibromide
either directly by injection into the crop, or indirectly in the diet
after fumigation, daily intakes being 0.5, 1, 2, 4 and 8 mg per day.
At 8 mg per day by both routes of administration, egg production was
depressed, while egg weight was reduced at all levels down to 0.5 mg
per bird, whether by crop or diet (Fuller & Morris, 1963).
Four bull calves were given a dose schedule averaging 2 mg/kg
body-weight daily of ethylene dibromide from the age of four days.
After 14-16 months, growth, health and libido of the treated bulls
were comparable to the controls, but sperm density was low and
motility poor. These changes were reversible (Amir & Volcani, 1965).
Short-term studies with fumigated foodstuff
When chickens were fed for five days, pigs for 12 days and heifers for
one week on grain previously fumigated with a gaseous mixture
containing 7.2 per cent ethylene dibromide none of them showed any
deleterious effects (Rowe et al., 1954).
Twenty-five adult hens, in groups of five, were given a ration made up
of 50 per cent sorghum. In those groups receiving grain containing
sorbed ethylene dibromide in amounts ranging from 50 to 320 ppm, there
was a decrease in egg weight proportional to the level of the
fumigant. Moreover, in those receiving the highest amount, egg laying
ceased completely in six-and-a-half weeks, and in those receiving 200
ppm it ceased within eight weeks. Even as little as 50 ppm had a
depressive effect on egg size within three weeks. Further, those hens
in which laying was arrested failed to resume when returned to a
normal ration (Bondi et al., 1955).
In another experiment with six-month-old hens in groups of 24 the
sorghum, making up 50 per cent of the grain fed, contained 10-15 ppm
ethylene dibromide and 20 ppm residual bromide, 20-30 ppm ethylene
dibromide and 50 ppm residual bromide and no free ethylene dibromide
but 120 ppm residual bromide. The fourth group was a control. Over 16
weeks the group receiving only the residual bromide behaved the same
as the controls, but those receiving ethylene dibromide showed a
decrease in egg size proportional to dose. But when these birds were
returned to a normal diet the egg size was regained (Bondi et al.,
In an experiment carried out with two groups each of five hens, all of
which were laying small eggs (40 per cent below normal) by being fed
grain containing ethylene dibromide, the administration to one group
of follicle stimulating hormone intravenously led to a partial
recovery in egg size. Moreover, there was no reaction between ethylene
dibromide and follicle stimulating hormone in sorghum. It is therefore
postulated that the ethylene dibromide acts on the formation or
release of pituitary follicle stimulating hormone (Olomucki, 1957).
A group of laying hens that was fed for 23 days with oats fumigated
with ethylene dibromide several months previously showed some
diminution of egg size compared with controls and when the grain had
been treated the day before with Dowfume EB5 (containing 63.6 per cent
carbon tetrachloride, 29.2 per cent ethylene dichloride and 7.2 per
cent ethylene dibromide by weight) at 10 times the recommended dose,
egg output and size declined rapidly in 10 days (Bierer & Vickers,
Five groups, each of 16 pullets six months of age, were fed for 19
(i) a protein laying ration, plus non-fumigated oats;
(ii) a protein laying ration, plus oats fumigated at the rate of 1.1
(iii) a protein laying ration, plus oats fumigated at the rate of 3.3
(iv) a commercial, all-mash ration, non-fumigated;
(v) a commercial, all-mash ration, the corn component of which had
been fumigated previously at the rate of 1.1 ml/kg.
The fumigant was a commercial mixture containing carbon tetrachloride
64 per cent, ethylene dichloride 29 per cent and ethylene dibromide 7
per cent. After fumigation the grain was allowed to air for two weeks.
In those groups which received fumigated oats, egg size was seriously
and significantly depressed, more so at the heavy dosage (when
production was totally arrested) than at the lower dosage. A smaller
but still significant depression of egg production was observed in the
birds on the mash ration containing fumigated oats subsequently ground
(Caylor & Laurent, 1960).
When ethylene dibromide is used as a fumigant on food products a small
amount of the compound may be converted to inorganic bromide by
reaction with the foodstuff, but the major part remains adsorbed to
the food in the unchanged form for some time.
There is little reason to believe that the limited changes brought
about chemically in the foodstuff by the action of ethylene dibromide
on its components are responsible for any significant changes in its
food value or for the production of any toxic substances.
The deleterious effects observed experimentally with the feeding of
fumigated rations to animals can be attributed, in all probability, to
the residue of unchanged ethylene dibromide.
The feeding studies carried out with ethylene dibromide, either fed
directly or as a residue after fumigation, were principally done with
poultry. This species seems particularly sensitive to the compound,
since experiments on other animals, though limited, give little
indication of toxicity. This action of ethylene dibromide on poultry
may be due to interference with the hormonal balance.
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 per 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.
On the available toxicological evidence, ethylene dibromide should be
used for fumigation of food only on the condition that no residue of
the unchanged compound will reach the consumer.
Further work required for unchanged ethylene dibromide
Further investigation of the effect of processing and cooking on
residual ethylene dibromide in food.
Short-term feeding studies in two mammalian species.
Reproduction studies for three generations in at least two species.
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.
RESIDUES IN FOOD AND THEIR EVALUATION
(a) Pre-harvest treatment
Ethylene dibromide has a fairly high phytotoxicity. Its pre-harvest
uses are confined to the treatment of soil before planting and to
certain, usually dormant, plants for quarantine purposes. Any residues
in food derived from such uses are likely to be minute and to occur as
(b) Post-harvest treatment
Ethylene dibromide is rarely used by itself. In a few countries it is
so used for stacked cereals in bags. It is used in many countries for
treating cereals, in mixtures with other liquid fumigants such an
ethylene dichloride and carbon tetrachloride. These mixtures are
usually applied to the surface of grain standing in bins or in holds
of ships. Ethylene dibromide is readily sorbed by individual grains
but, when poured on to grain it only penetrates a short distance. This
also pertains even when mixtures are used in this manner, since
separation of the constituents rapidly occurs (Berck, 1961; Berck &
Solomon, 1962). This chemical therefore is used sometimes in liquid
grain fumigants to ensure an adequate treatment of the surface layers,
where the highest concentrations of insects are frequently found. When
such mixtures are applied to the surface of a bulk, the proportion of
the grain present which comes into contact with ethylene dibromide is
usually quite small; furthermore, samples carefully taken from surface
layers may have high residues whereas the main volume of grain present
may not contain any fumigant. Mixtures are also used for the "spot
fumigation" of individual items of machinery in milling plants.
Ethylene dibromide is used on fresh fruit such as citrus, mainly as a
quarantine measure against fruit fly. It is also sometimes used in a
mixture with other fumigants, such as ethylene dichloride and carbon
disulfide, on some other stored foods, such as pulses, and on various
non-edible products. Fresh fruits may sorb some fumigant but with
thick-skinned fruits such as citrus, these residues appear to be
concentrated in the skins and penetration into the flesh of undamaged
fruit appears to be small (Page & Blackith, 1956; Grierson & Hayward,
1959; Coggiola & Huelin, 1964). Ethylene dibromide is also used for
the fumigation of empty wagons.
There are no tolerances for residues of unchanged ethylene dibromide.
For inorganic bromide derived from fumigation there are tolerances of
50 ppm in Brazil, Germany, India, the Netherlands, USA and Canada;
there is a tolerance of 20 ppm in Czechoslovakia and New Zealand.
Residues resulting from supervised trials
The fumigant is sorbed very readily by cereals or cereal products
during exposure period (Whitney & Kenaga, 1960; Heuser, 1964).
Although nearly all of the fumigant taken up by the cereals appears to
be physically sorbed and can be removed by airing, this is a very slow
process by comparison with the removal of methyl bromide. Therefore
there is a greater chance of unchanged fumigant remaining in food.
When whole or ground wheat was fumigated experimentally at 8 g/m3 or
16 g/m3 for 24 hours, more than 95 per cent of the ethylene
dibromide could be recovered unchanged after 10 days; most of it was
retained in the bran. Very little was converted to ionized bromide.
Residues in milled samples after 35 days amounted to 4.5 ppm
(Sinclair, Lindgren & Forbes, 1962). The very small proportion of the
sorbed fumigant which combines appears to react mainly with the
protein, or to change into inorganic bromide. This may result in a
very slight change in the nature of the food protein itself, probably
in its methionine component (Bridges, 1956).
Coggiola & Heulin (1964) found the uptake of ethylene dibromide by
treated oranges during treatment to increase with the period of
storage of the fruit before fumigation. These authors also found that
the losses of residue after treatment were greater with longer periods
of pre-fumigation storage. One hundred and fifty gram oranges stored
one to 25 days before fumigation absorbed from approximately 30 mg to
35 mg (respectively) of ethylene dibromide per orange; subsequent loss
of residue varied from about zero up to over 5 mg per orange after 30
Getzendaner (1965) has investigated the residues of various mixed
commercial fumigants based on ethylene dibromide in milled wheat
products following spot-fumigant treatment of mill machinery. For a
mixture of 59 per cent ethylene dibromide with 32 per cent carbon
tetrachloride and nine per cent ethylene dichloride residues up to
1000 ppm of organic bromide were found immediately following
fumigation, but giving way to pre-fumigation levels (10-20 ppm total
Br. 0-4 ppm organic Br.) fairly quickly. 20.4 per cent ethylene
dibromide with 57 per cent carbon tetrachloride, 19.6 per cent
ethylene dichloride gave somewhat lower bromide residues in the flour
immediately after fumigation (200-300 ppm) falling quickly to
pre-fumigation levels. Getzandaner (1965a) 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) showed that the feeding of fumigated cereals to cattle may
lead to bromide residues in milk. Lynn (1963) found 20 ppm bromide in
milk from cows fed a diet containing 43 ppm bromide.
Berck (1965) has shown that under laboratory conditions the uptake of
ethylene dibromide by wheat increases significantly with increase of
moisture content from nine to 18.5 per cent; the same is true of
ethylene dichloride but not of carbon tetrachloride. Comminution, as
in milling, greatly increased the uptake. The chromatographic
characteristics of 51 different cereals (or cereal products) towards
mixed fumigants was also studied.
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; the
findings are summarized in Table I; but Heywood (1966) pointed out
that not all of this bromide could be attributed to the use of
fumigants since some occurs naturally in food.
TABLE 1. BROMIDE RESIDUES IN TOTAL DIET STUDIES
Foods Bromide range ppm Number of samples
(out of 18)
Dairy products 1.1 to 31.7 17
Meat, fish 2.3 to 35.5 16
TABLE 1. (cont'd)
Foods Bromide range ppm Number of samples
(out of 18)
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
An examination of 227 grain shipments to the Netherlands from all
parts of the world in the period May 1964 to September 1961, showed
inorganic bromide residues to be present in only 12 of these. Methods
for the measurement of unchanged residues of ethylene dibromide are
still being developed but preliminary observations on these shipment:
showed unchanged ethylene dibromide to be present in one sample only
(approximately 0.5 ppm).
Although results are available from a number of pilot scale trials
using commercial sale, handling and milling facilities (e.g. Lynn &
Vorkes, 1957), very few data are available for commercially marketed
cereals. Because of the manner in which the fumigant separates out
when liquid fumigant mixtures are applied to the surfaces of grain
standing in tins, measurable residues may only be found in the surface
layer of the grain present: reports on residues found should therefore
give details of the sampling method used.
Fate of residues
In plants and animals
Little work appears to have been done on mechanisms by which ethylene
dibromide produces toxic effects in plants and animals or on its fate
when it has been absorbed. Residues of "apparent organo bromine
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 and the results (some of which are reproduced on page 121)
probably reflect naturally occurring bromide in the various plants.
In storage and processing
Ethylene dibromide in wheat and wheat products is very resistant to
dispersion by airing. Toxic effects on animals, particularly poultry,
have resulted from consumption of food treated with this fumigant.
These effects have usually followed feeding relatively soon after a
treatment, bearing in mind the low rate of dispersion, and seem to be
attributable to the presence of free ethylene dibromide. Almost all
traces of ethylene dibromide appear to be lost by volatilization on
heating as in baking (Senger & Mapes, 1957; Munsey, Mills & Klein,
1957) but according to Bridges (1956) some breaks down to produce
minute amounts of ethylene glycol which may react with the - SCH3 of
the methionine in the wheat protein. The joint meeting of the FAO
Committee on Pesticides in Agriculture and the WHO Expert Committee on
Pesticide Residues (FAO/WHO, 1965) recommended that the effects of
processing and particularly of cooking on the residues of ethylene
dibromide in foods should be further investigated.
Methods of residue analysis
In sampling cereals for ethylene dibromide residue analysis, special
attention must be paid to the extent to which the sample is
representative of the bulk. Analysis of residues of ethylene dibromide
in cereals, which are mostly present in the unchanged organic form, is
usually based on the measurement of total organic and inorganic
bromine, measured as bromide. For this, there are a number of well
established methods based on the hydrolysis of ethylene dibromide with
alkali to inorganic bromide, evaporation to dryness of the resultant
mixture, removal of the organic matter by controlled ignition,
extraction by dilute acid of the total bromide from the resultant ash,
oxidation to bromate, the liberation by this of iodine from acid
potassium iodide and the determination of the iodine titrimetrically
with sodium thiosulfate (Mapes & Shrader, 1957; Heuser, 1961). The
inorganic bromide residue alone may similarly be determined after
removal of unchanged ethylene dibromide by aeration (Heuser, 1961.).
Unchanged ethylene dibromide can then be calculated by difference. The
limit of detection by this procedure is of the order of 1 ppm as
bromide. Berck (1965) has published details of a gas chromatograph
method for the detection and measurement of some 34 fumigant vapours,
including ethylene dibromide. This general technique has recently been
applied by Bielorai & Alumot (1965) to the measurement of residues of
unchanged ethylene dibromide in experimentally fumigated animal feeds:
its application to the determination of such residues in commercially
fumigated foods is most desirable.
The method for the determination of total and inorganic bromide
derived from the use of ethylene dibromide on cereals based on that of
Heuser (1961) is in the meantime suggested. Details are set out in
Appendix A(1) of the (Extract) Report of the Second Session of the FAO
Working Party on Pesticide Residues (PL/1965/12).
RECOMMENDATION FOR TOLERANCES
On the basis of an acceptable daily 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 ethylene dibromide and
other fumigants can be recommended. This recommendation is also
consistent with tolerance for dried eggs, processed herbs and spices
at 400 ppm, various fresh fruits at 200 ppm, citrus at 230 ppm,
raisins and 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 use of the fumigant and which
are as follows:
Dried eggs, spices, herbs 400
Dried figs 250
Dried raisins, dates 100
Dried peaches 50
Dried prunes 20
Other dried fruits 30
Citrus, strawberries 30
Other fresh fruit 20
In the absence of a recommendation for an acceptable daily intake for
unchanged ethylene dibromide and as there appear to be no very strong
practical or economic reasons for accepting such residues, no
recommendations are made for a tolerance for residues of this
The joint FAO/WHO Expert Committee on Food Additives (FAO/WHO, 1964),
when considering the presence of bromide in bread due to the addition
of bromate conditioner to flour, gave estimates of acceptable levels
for 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.
Further work or information
Further data are needed on the occurrence of residues in raw and
processed foods after use of the fumigant under practical conditions.
Measurement of residues in foods resulting from the use of mixed
fumigants, including ethylene dibromide, is desirable.
Gas-liquid chromatographic methods should be particularly useful for
the determination of residues of unchanged ethylene dibromide in
cereals. The method offers the prospect of increased sensitivity and a
means for the simultaneous determination of other fumigants which may
be present. It should now be possible to develop a rapid, selective,
quantitative technique for traces of halogenated fumigants, together
with suitable desorption techniques, and to combine these into a
single method for the determination of residues in treated foods and
the Working Party recommends accordingly. Figures for the levels of
any unchanged ethylene dibromide in commercially treated materials
particularly those which have a relatively high oil or fat content,
would also be useful.
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