WHO/Food Add./68.30



    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)

    Rome, 1968


    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 :



    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.


    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


    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              -


    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

    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

    Pea/Bean              0              4               5-10              2.0-5.0     2

    Corn                  0              0               12-21             -           2

    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


    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

    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.


    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)).


    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.


    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


    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


    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 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.


    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

    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.

    See Also:
       Toxicological Abbreviations
       Diazinon (EHC 198, 1998)
       Diazinon (ICSC)
       Diazinon (FAO Meeting Report PL/1965/10/1)
       Diazinon (FAO/PL:CP/15)
       Diazinon (FAO/PL:1968/M/9/1)
       Diazinon (AGP:1970/M/12/1)
       Diazinon (WHO Pesticide Residues Series 5)
       Diazinon (Pesticide residues in food: 1979 evaluations)
       Diazinon (Pesticide residues in food: 1993 evaluations Part II Toxicology)
       Diazinon (JMPR Evaluations 2001 Part II Toxicological)