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
DIAZINON
This pesticide was evaluated for acceptable daily intake by the 1965
Joint Meeting of the FAO Committee on Pesticides in Agriculture and
the WHO Expert Committee on Pesticide Residues (FAO/WHO, 1965). As no
additional toxicological data has become available since the previous
publication, the following monograph addendum is confined to :
EVALUATION FOR TOLERANCES
USE PATTERN
The following information was obtained from : Geigy Chemical Corp.,
Pesticide petitions submitted to the U.S. Food and Drug Administration
1956 to 1967; U.S. Dept. of Agriculture Handbook No. 331; U.S. Dept.
of Agriculture Summary of Registered Agricultural Pesticide Chemical
Uses, 1964 to 1967.
Pre-harvest treatments
Diazinon is used as a dust or spray formulation on over 60 food and
feed crops including most fruits, vegetables, forages and hays.
Table I summarizes typical dosages and pre-harvest periods for the
various crop categories. Diazinon has been found effective in
controlling over 100 species of food crop pests such as mites, aphids,
thrips, maggots, fruitflies, worms, beetles, grasshoppers, leaf
miners, etc.
Seed furrow soil treatments are used for several root vegetable crops.
Dermal applications are made on sheep and cattle to control horn
flies, ticks and lice.
TABLE I
Crop Actual Dosage Pre-harvest
Period, days
Tree fruits 0.5 lb/100 gal (full coverage) 10-20
Caneberries 1.0 lb/acre (full coverage) 7
Citrus 0.5 lb/100 gal (full coverage) 7-21
Leafy vegetables 0.5-1.0 lb/acre 5-21
Root vegetables 0.5-1.2 lb/acre 10
Others 0.25-1.0 lb/acre 0-7
TABLE I (cont'd)
Crop Actual Dosage Pre-harvest
Period, days
Forages and Hays 0.5-1.0 lb/acre No grazing limitations
4-10 days before cutting hay
Cattle and Sheep 1.0-2.3 gal of 0.03-0.05% 14 pre-slaughter period
spray per animal
Post-harvest treatments
There is no commercial post-harvest use of diazinon.
Other uses
Diazinon is recommended for fly control in dairy barns and other farm
buildings as well as in food processing plants; however, this is
becoming less important because of resistance. It is commonly used in
households as a mothproofing agent to control carpet beetles and
clothes moths, and is also used in home gardens and in public
buildings to combat ants, cockroaches, firebrats, etc.
RESIDUES RESULTING FROM SUPERVISED TRIALS
In numerous experiments conducted in the U.S.A., Canada and several
other countries residues were determined at various time intervals
after multiple applications of varying amounts of diazinon on over 60
crops. For example, in the controlled experiments for apples, 16
varieties of apples were treated in 15 states in the U.S.A. using 1/2
to 1 lb/100 gal (full coverage sprays) on various spray schedules and
in combination with other pesticides and fungicides.
A summary of the numerous data (mostly unpublished material) obtained
from the rates of application shown in Table I is given in Table II.
TABLE II
Typical Residues
Crops Initial Pre-harvest at Pre-harvest Entimated
Residues Period Period Indicated Half-life
ppm days ppm days
Tree Fruits
Apples 0.6-0.8 14 0.1 5
TABLE II (cont'd)
Typical Residues
Crops Initial Pre-harvest at Pre-harvest Entimated
Residues Period Period Indicated Half-life
ppm days ppm days
Pears 0.6-0.7 14 0.1-0.3 5
Cherries 3-7 10 0.1-0.3 3
Peaches 2-6 20 0.1-0.6 3-6
Apricots 1-2 10 0.1 2
Nectarines 1-2 10 0.2 3-4
Plums 2-4 10 0.1-0.2 2
Figs 0.5 10 <0.1 3
Citrus
Oranges 3-5 21 0.1-0.4 4
Lemons 4.0 21 0.6-0.7 6-7
Grapefruit 0.3 7 0.1-0.2 7
Caneberries and Small Fruit
Strawberries 0.9-1.4 5 0.2-0.4 2-4
Grapes 1-8 18 0.1-0.3 3
Cranberries 9 7 <0.1 1
Blueberries 1-4 7 0.1-0.3 1-2
Blackberries )
Boysenberries) 2.5-5 7 0.1-0.3 2
Loganberries )
Raspberries )
Leafy Vegetables
Cabbage 1-2.5 7 0.3-0.7 4-6
Celery 7-9 10 <0.1-0.3 2
Cauliflower 0.8 5 0.4-0.5 7
Broccoli 1-2 5 0.5 3
Lettuce 6-17 10 0.3-0.5 1-2
Spinach 5-8 10 <0.1-0.2 2
Endive 3 10 0.1 2
Collards 3 12 <0.1 2
Kale 10-24 12 0.1-0.2 1
Parsley 1-6 12 0.1 2
Swiss Chard 2 12 <0.1 2
Turnip Greens 4-15 12 <0.1 2
Vegetable Root
Beets <0.1 0
Onions 7-13 (green) 10 (green) 0.4-0.6 (green) 2
2-3 (dry) 10 (dry) 0.2-0.3 (dry) 2
TABLE II (cont'd)
Typical Residues
Crops Initial Pre-harvest at Pre-harvest Entimated
Residues Period Period Indicated Half-life
ppm days ppm days
Carrots 1-2 10 0.1-0.3 2-3
Parsnips 0.7 10 0.3 6
Radishes 0.2-0.4 10 <0.1 4
Turnips 0.5 10 0.4-0.5 21
Vegetables (Others)
Peppers 0.6-0.8 5 0.1-0.2 2-3
Cucumbers 1.0-2.5 7 <0.1 2
Green beans 1-2 7 <0.1 2
Lima beans 0.2-1.0 7 <0.1-0.2 2
Squash 0.1-0.2 3 <0.1-0.2 2
Corn (ears only) <0.1 0 <0.1 -
Peas (plus pod) <0.1 0 <0.1 -
Miscellaneous
Tomatoes 0.1-0.4 3 <0.1-0.2 2
Melons 0.1-0.7 3 <0.1-0.2 2-3
Olives 1-6 75 <0.2-0.6 ca 25
Hops (cones) 3-11 14 0.1-0.3 3
Sorghum (grain) 0.5 7 < 0.1 2
Pre-slaughter
Meat Period
Lamb fat 1-3 14 0.1-0.5 5
Beef fat 1-3 14 <0.1-0.2 3
Pre-grazing Initial residue Residue
Forages interval Cutting Time In forage at cutting Half-life
days days ppm ppm days
Alfalfa 0 7 12-24 0.2-0.5 2
Clover 0 7 4-14 1.0-4.0 2-3
Range/Pasture grass 0 21 9 4.0-7.2 2-3
30 54
(oil
formulation)
Pea/Bean 0 4 5-10 2.0-5.0 2
Corn 0 0 12-21 - 2
RESIDUES IN FOOD MOVING IN COMMERCE
Of some 14,800 randomly selected samples of raw agricultural products
examined by the U.S. Food and Drug Administration from June 1965
through 1966, only 32 samples showed any detectable residue of
diazinon.
FATE OF RESIDUES
In soils
Since diazinon is used to some degree as a soil treatment, the fate in
soil is important with respect to root crops grown in those soils even
though there is no reported systemic action for diazinon.
Laygo and Schulz (1963) studied the persistence of organo-phosphorus
insecticides in the microfauna in soils. Using Drosophila
melanogaster assays, diazinon disappeared from the top soil layers
within 9 days.
Getzin and Rosefield (1966) treated four soil types with diazinon-14C
under laboratory conditions and conducted a field trial with 5-6 lbs
per acre soil treatment. Results indicated that 50 per cent of the
initial residue remained after 4 weeks. Dissipation progressed more
slowly after 8 weeks with 10 per cent or 0.2 ppm diazinon remaining
after 24 weeks.
In plants
It can be seen from the data in Table II that diazinon does not
persist long as a residue on most food plants as determined by the
sulfide and the phosphorus procedures. It was generally considered
that the sulfide procedure was the most reliable measure of residues
of diazinon in plants; however, to make sure that no significant
anticholinesterase phosphate derivatives (such as oxo-diazinon, the
P=0 oxygen analog which contains no sulfur) remained, some residue
data were acquired in 1956 by the anticholinesterase method. These
data showed that no significant residues of oxodiazinon remained on
the products tested (Geigy, 1956). It was not until fairly recently
that a more comprehensive study was made on the nature of residues on
plants.
Coffin and McKinely (1964) reported on the metabolism and persistence
of diazinon on field sprayed lettuce. Diazinon residues decreased from
8.1 ppm to 0.3 ppm from 4 hours to 7 days after spraying, and
detectable quantities of diazinon were present at 10 and 14 days. No
significant amount of oxodiazinon or other metabolites were found by
the paper chromatographic detection system.
Ralls, et al. (1966) studied the fate of 35S-labelled diazinon on
field grown crops and found a rapid decrease in diazinon residues. The
metabolite identified from field samples was oxodiazinon. Three
thin-layer chromatographic systems showed the presence of this
metabolite on spinach at 0.005 to 0.01 ppm 5 days after spraying.
Paper chromatography of snap bean extracts harvested 7 days after
treatment showed an increase in a cholinesterase inhibiting compound
with an Rf value corresponding to oxodiazinon.
Additional studies on the field incurred residue levels of diazinon
(I), oxodiazinon (II) and 2-isopropyl-4-methyl-pyrimidin-6-ol (III)
were made by Ralls and co-workers (1967) using diazinon-32P. A
spinach sample analyzed one hour after spraying contained 31.7 ppm
(I), 1.5 ppm (II) and 2.5 ppm (III). Analysis of a 4 day sample gave
1.8 ppm (I), 0.34 ppm (II) and 2.5 ppm (III). Although diazinon and
its oxygen analog dissipated rapidly, compound (III), the result of
further hydrolysis of oxodiazinon, persisted at the same level. The
mammalian toxicity of this persistent compound is not known. Similar
experiments with snap bean and tomato plants showed the same rapid
disappearance of diazinon and oxodiazinon to levels greatly below 0.1
ppm after 4 days. Less than 0.1 ppm of compound (III) was found in all
4-day samples.
Grasses and grains grown for forage which had been treated with
diazinon were analyzed by the sulfide procedure. Maier-Bode (1963)
found diminution of residues occured only in the uncut grasses. After
cutting and while drying to hay, little of the diazinon was lost.
In animals
Robbins et al (1957) administered 32P-labeled diazinon orally to a
cow at 20 mg/kg level. Much of the diazinon was rapidly metabolized
and excreted. About 74 percent of the dose, excreted as polar
degradation products, was accounted for in the urine 36 hours after
treatment. The main 32P-labeled end products of diazinon metabolism
in the cow were found to be diethyl phosphorothioic and diethyl
phosphoric acid. From this extreme rate of administration residues of
0.09 to 0.56 ppm appeared in milk at from 6 to 24 hours after
administration. No residues were found after 24 hours.
Rai and Roan (1959) found no residues of diazinon in the milk of dairy
animals given daily oral doses of diazinon at the rates of 1.06, 5.30
and 10.60 mg/kg of body weight over a 3 week feeding period. These
administration rates are calculated to be 100, 500 and 1000 ppm on the
basis of the grain fed, or 51, 290 and 500 ppm on the basis of hay
consumed. Steers treated with 165 and 825 ppm in daily oral doses
calculated on the bases of grain fed showed traces of diazinon in
blood, urine, muscle, liver and brain. Only in fat was a significant
residue found of 0.23 ppm at the maximum feeding level. These results
were obtained by the use of three methods of analysis; a sulfide, an
anticholinesterase and a bioassay method.
Derbyshire and Murphy (1962) fed cows at the rate of 500 ppm
calculated on dry matter intake and found no residue in milk.
Diazinon residues in the fat of sprayed cows has been reported one and
seven days after the last application, but none was present after a
post-spray interval of 14 days. (Claborn et al., 1953).
In storage and processing
Residue levels of diazinon, oxodiazinon and
2-isopropyl-4-methyl-pyrimidin-6-ol were measured in snap beans,
spinach and tomatoes subjected to washing, blanching and peeling (for
tomatoes) under simulated commercial conditions (Ralls et al, 1967).
Diazinon on spinach at harvest 4 days after spraying was present at
1.8 ppm and oxodiazinon at 0.34 ppm. A spray rinse did not
significantly reduce residues. Detergent washing reduced diazinon to
0.77 ppm and oxodiazinon to 0.18 ppm, and steam blanching gave a total
reduction to about 30 percent of the original residue. Only a water
blanching process significantly reduced the level of pyrimidinol
metabolite from 2.5 ppm to 0.1 ppm. Residues at harvest (8 days) on
snap beans and tomatoes were less than 0.1 ppm. Subsequent
commercially simulated treatment appeared to have little or no effect,
except possibly the commercial peeling of tomatoes.
No data is available on the effect of freezing, canning, etc.
RESIDUES IN FOOD AT TIME OF CONSUMPTION
Total diet studies conducted during 1965 and 1956 by the U.S. Food and
Drug Administration revealed that 98 percent of the food samples
contained no detectable residues of diazinon. The remaining 2 percent
contained only trace quantities. A multidetection gas chromatographic
method using an electron capture detector and/or a thermionic detector
specific for phosphorous was used for the analyses. The sensitivity of
the method was about 0.05 ppm (Duggan et al. (1967)).
METHODS OF RESIDUE ANALYSIS
Most of the residue data summarized in this monograph were obtained
using one or two of four different methods of analysis developed by
Geigy Chemical Company (1956-1967).
A sulfide procedure was considered the most accurate when spray
history was known. In this procedure diazinon is extracted from crops
with a solvent and from the solvent with 48 percent HBr. The 48
percent HBr treatment adds a high degree of selectivity for the
determination of diazinon. Upon boiling the acid solution, diazinon
sulfur is converted to H2S and distilled off. It is collected in zinc
acetate solution and then converted to a methylene blue complex which
is determined spectrophotometrically. Sensitivity of the sulfide
procedure is about 0.1-0.2 ppm. Some crops such as kale had high
natural sulfur blanks so these crops were analyzed by a phosphate
method. Thiocarbamates such as ferbam also interfere and must be
removed by an additional cleanup step.
Some phosphorothioates are known to form relatively stable metabolic
products containing no sulfur for which the method described above
would not be applicable, so a cholinesterase inhibition method was
utilized to validate the sulfide procedure.
The method based on determining the phosphorous of diazinon and one
based on the ultraviolet absorption properties of the pyrimidine
portion of the molecule were fraught with high blank and cleanup
problems. Sensitivity of these methods is about 0.3-0.4 ppm.
None of these four methods were of adequate sensitivity or specificity
for "total diet" samples. Such data were not possible until the GLC
methods based on electron capture and thermionic detectors were used.
The methods of Storherr and co-workers (1964 and 1965) using an ethyl
acetate extraction and either a sweep co-distillation or celite column
cleanup with gas chromatographic detection provide a rapid and
adequately sensitive procedure for diazinon in most food commodities.
J.R. Geigy S.A. has developed a gas chromatographic method which is
applied following a shakeout with 48 percent HBr. The gas
chromatographic methods are sensitive to about 0.01 ppm or better. A
number of thin layer chromatographic procedures described in the
literature will provide a confirmative test.
RECOMMENDATIONS FOR TOLERANCES
Temporary tolerances
When diazinon is utilized in accordance with good agricultural
practice to protect food, when necessary, against insect infestation,
the treated product may have residues as high as those shown below :
Peaches and citrus 0.7 ppm
Other fruits 0.5 ppm
Leafy vegetables 0.7 ppm
Other vegetables 0.5 ppm
Meat (fat basis) 0.5 ppm
By no means will all samples of these products contain this amount of
residue; in fact only a small, yet unknown, portion of each product in
these categories is likely to be treated. Also there are some data
available showing that a significant amount of reduction in residues
will take place during washing and other preparation and processing of
NATIONAL TOLERANCES
Country Tolerance, ppm Crop
Canada 0.25 melons, figs, cranberries and 7 vegetables
0.5 beans, Brussels sprouts, cucumbers, turnips
0.75 tree fruits including citrus, grapes,
strawberries, and 16 vegetables.
Germany (west) 0.5 on or in vegetables, fruits, root crops,
legumes, grapes and hops.
Hungary 5 food
India 0 (proposed) cereals
Italy 2 olive oil
Netherlands 0.5 on or in
1) vegetables or parts thereof for consumption,
including edible mushroome and edible roots,
bulbs and tubers.
2) edible fruits of vegetables and fruit crops
or parts thereof.
Switzerland The Swiss intercantonal commission for toxic materials ("Commission Intercantonale
des Toxiques") proposes a tolerance of 0.5 ppm. Federal regulations are in preparation.
U.S.A. 0.75 ca 25 fruits and 25 vegetables, fat of meat
and meat by-products of cattle and sheep.
1 olives and olive oil
3 almond hulls
10 5 hays
NATIONAL TOLERANCES (cont'd)
Country Tolerance, ppm Crop
25 bean and pea forage
40 alfalfa, clever and corn forage
60 pasture grasses
food for consumption. Other data which give support to the above
factors is that in the U.S.A. "total diet" samples diazinon is seldom
found and when found it is at a low level. The meeting is convinced
that under the conditions of practical use the above residues on
products which need to be protected will not produce a total diet
which will contain an amount of diazinon in excess of the ADI.
Therefore, it is recommended that a temporary tolerance be adopted for
a period ending December 31, 1970, for the residue values for the
products shown above.
FURTHER WORK
Further work required before 30 June 1970
1. More data on the amount and persistence of the oxygen analog on
food crops.
2. Further data on the effect of food preparation and processing on
the reduction of residues.
3. Data on the amount and persistence of the pyrimidinol moiety of
the compound.
REFERENCES PERTINENT TO EVALUATION FOR TOLERANCES
Claborn, H.V., Mann, R.D., Younger, R.L. and Radeleff, R.D. (1963)
Diazinon residues in the fat of sprayed cattle. J Econ. Entomol. 56
(6): 858 - 9.
Coffin, D.E. and McKinely, W.P. (1964) The metabolism and persistence
of Systox, Diazinon and Phosdrin on field-sprayed lettuce. J. Assoc.
Off. Agr. Chem. 47 (4): 632 - 40.
Derbyshire, J.C. and Murphy, R.T. (1962) Diazinon residues in treated
silage and milk of cows fed powdered diazinon. J. Agr. Food Chem. 10
(5): 384 - 6.
Duggan, R.E., Berry, H.C. and Johnson, L.Y. (1967) Pesticide residues
in total diet samples II. Pest. Monitor. J. 1 (2), 2 - 12 (1967).
FAO/WHO. (1965) Evaluation of the toxicity of pesticide residues in
food. FAO Meeting Report 1965/10/1; WHO/Food Add./27.65
Geigy Chemical Co. (1956 -1967) Unpublished data and methods of
analysis in pesticide petitions submitted to the U.S. Food and Drug
Administration.
Geigy, J.R. Basle, Switzerland. Analytical method for determination of
diazinon (unpublished).
Getzin, L.W. and Rosefield, I. (1966) Persistence of diazinon and
zinophos in soils. J. Econ. Entomol. 59 (3) : 512 - 16.
Laygo, E.R. and Schulz, J.R. (1963) Persistence of organophosphate
insecticides and their effects on microfauna in soils. Proc. N. Dakota
Acad. Sci. 17: 64 - 6.
Maier-Bode, H. (1963) Residues of insecticides on cover crops growing
in orchards after application of organic phosphorus toxicants on the
trees. Z. Pflanzenkrankh. Pflanzenschutz. 70 (80): 449 - 59.
Rai, L. and Roan, C.C. (1959) Report included in Geigy Chemical Co.
pesticide petition to the U.S. Food and Drug Administration.
Ralls, J.W. Gilmore, D.R., and Cortes, A. (1966) Fate of radioactive
0,0--diethyl 0-(2-isopropyl-4-methylpyrimidin-6-yl) phosphorothioate
on field grown experimental crops. J. Agr. Food Chem. 14 (4) :
387 - 92.
Ralls, J.W. Gilmore, D.R. Cortes, A., Schutt, S.M. and Mercer, W.A.
(1967) Residue levels of diazinon and its transformation products on
tomatoes, spinach and beans. Food Technology 21: 92 - 4.
Robbins, W.E., Hopkins, T.L. and Eddy, G.W. (1957) Metabolism and
excretion of phosphorus-32-labeled diazinon in a cow. J. Agr. Food
Chem. 5 (7); 509 - 13.
Storherr, R.W., Getz, M.E., Watts, R.R., Friedman, S.J. Erwin, F.,
Giuffrida, L. and Ives, F. (1964) Identification and Analyses of five
organophosphate pesticides: Recoveries from crops fortified at
different levels. J. Assoc. Off. Agr. Chem. 47 (6): 1087 - 93.
Storherr, R.W. and Watts, R.R. (1965) A sweep co-distillation cleanup
method for organophosphate pesticides. J. Assoc. Off. Agr. Chem. 48
(6): 1154 - 60.