THIABENDAZOLE                                   JMPR 1972


    In 1970 the Joint Meeting evaluated the available data on
    thiabendazole, and an ADI of 0.05 mg/kg/day was recommended (FAO/WHO,
    1971). Tolerances were proposed for citrus fruit and bananas to take
    account of the use of this fungicide for post harvest treatments. In
    1971 recommendations were made for the residues resulting from the
    treatment of pome fruit (FAO/WHO, 1972). Since that time, considerable
    quantities of citrus fruit and bananas have been treated with
    thiabendazole and much of this has entered international trade.

    Studies have shown that for satisfactory inhibition of sporulation of
    moulds which stain citrus fruit and produce unacceptable odour, taste
    and appearance, every fruit must be treated in such a way that an
    adequate deposit of thiabendazole is left on the skin. The minimum
    effective concentration on the skin is equivalent to 6-7 ppm on the
    whole fruit. To ensure that this level is maintained, some fruit
    should receive up to 10 ppm thiabendazole, the level depending on skin
    texture, fruit size and method of applying the wax.



    The application of thiabendazole to citrus fruit, including dipping
    and spraying with suspensions and the incorporation in the wax used
    for preventing moisture loss during storage, shipment and marketing,
    is extensively practised in the U.S.A., Israel, Australia and South

    The citrus fruit industry in several countries, including the U.S.A.,
    Israel and South Africa, has found that the dipping process is not
    compatible with production methods and equipment used routinely in
    packing houses. The installation of equipment, space and drying
    facilities to allow the introduction of a dipping process would entail
    additional costs and slow down fruit processing. Admixture with wax
    emulsions is therefore preferred (Anon., 1972).

    One of the objectives in applying thiabendazole to citrus fruit is to
    avoid the necessity of using diphenyl impregnated wraps, liners or
    inserts in the packages (Eckert and Kolbezen, 1971a). To date, citrus
    fruit packing houses - at least in the U.S.A. - have been reluctant to
    discontinue the use of diphenyl while there was a possibility that
    citrus fruit treated with thiabendazole at rates below the tolerance
    limit of 6 ppm might allow the development of some mouldy fruit. To
    avoid significant spoilage and soiling, all thiabendazole treated
    fruit has also been protected by diphenyl.

    Work at the University of California (Eckert and Kolbezen, 1971b) has
    shown that citrus fruit treated with thiabendazole in wax emulsion is
    as well protected against sporulation as similar fruit protected with
    diphenyl, provided the concentration on the skin is sufficiently high.

    Data on extensive trials were supplied to the Joint Meeting (Anon.,
    1972) with a request that the 6 ppm tolerance be revised to
    accommodate the higher rate of application needed. The results of
    these trials indicate that a significant proportion of the fruits in
    any consignment will contain residues of thiabendazole approaching 10
    ppm on the whole fruit.


    Results of packing house trials carried out in Israel with fruit
    shipped to and analysed in the Netherlands in 1970 show that when 150
    fruit from 13 consignments (10 - 20 from each) were analysed for
    thiabendazole residues, the overall average was just under 3.0 ppm.
    The variation in residue levels on individual fruits ranged from
    0.43 - 7.35 ppm (FAO/WHO, 1971).

    The Netherlands Delegation to the Codex Committee on Pesticide
    Residues carried out a statistical analysis of the data and showed
    (Kruysse, 1971) that for each of the 13 consignments the upper 95%
    confidence limit ranged from 1.18 to 8.92 ppm. Six of the 13
    consignments were estimated to contain fruit with residues above the
    tolerance limit of 6 ppm notwithstanding the average of 3 ppm. This
    indicates that under practical conditions many consignments would
    violate the tolerance if it remained at 6 ppm.

    Trials carried out at the University of California (Eckert and
    Kolbezen, 1971a and 1971b) on numerous varieties of citrus fruit
    demonstrated that wax emulsion containing approximately 5 000 ppm
    (0.5%) thiabendazole would give surface residues of sufficient
    magnitude to inhibit the growth and sporulation of Penicillium
    digitatum on the surface of decaying oranges. The lack of uniformity
    of residue from one fruit to another in any lot of fruit which has
    been treated by commercial equipment makes it necessary to recommend
    concentrations well above the minimum effective levels determined in
    controlled experiments.

    Table 1 gives the level of thiabendazole residues found on citrus
    fruit treated with a water-emulsion wax containing several levels of
    thiabendazole (Anon., 1972).

    Fourteen large citrus fruit packing houses took part in officially
    supervised trials to determine the efficiency of thiabendazole/wax
    treatment for reducing sporulation and preventing wastage. The fruit
    was stored under conditions typical of shipping, and portions were
    exported to Europe where the cartons and contents were inspected by
    inspectors from the U.S. Department of Agriculture.

    TABLE 1  Residues of thiabendazole on citrus fruits treated
             with a water emulsion wax


    Formulation1                    mg TBZ/kg fresh fruit2 3
    (mg TBZ/kg wax)          Orange         Lemon         Grapefruit

    Initial 1965              1.25           1.94           2.79
    Final 1965                1.06           1.97           2.61
                              1.22           1.85           2.74
                              1.08           2.32           2.35
                              1.06           1.80           2.74
                              1.30           1.92           3.29
    Mean                      1.160.11      1.960.18      2.750.30

    Initial 3065              3.53           5.32           3.51
    Final 4244                3.69           4.23           3.48
                              4.41           4.96           4.59
                              4.38           6.02           4.95
                              3.58           4.13           4.48
                              3.37           5.47           4.82
    Mean                      3.820.44      5.020.73      4.300.64

    Initial 5784              5.65           8.41           4.68
    Final 6206                5.65           9.19           4.86
                              5.80           7.77           4.86
                              5.71           7.39           5.49
                              8.32           8.41           5.73
                              5.36          10.25           5.84
    Mean                      6.081.09      8.571.04      5.310.48

    Initial 8869             11.4           14.0            9.6
    Final 8383                9.4           13.6           11.4
                             11.8           13.4            8.9
                             12.2           15.2           11.6
                             12.8           14.1            9.6
                             12.9           13.3           10.5
    Mean                     11.71.3       13.90.7       10.21.1

    1    Samples collected at spray nozzle before and after fruit treated.

    2    Values obtained by analysis of individual fruit. Value following
         mean is the standard deviation.

    3    Average surface areas: orange - 141 cm2, lemon - 128 cm2,
         grapefruit - 231 cm2.

    It was demonstrated that all varieties of citrus can be protected
    during shipment, provided the total thiabendazole deposit exceeds
    6 - 9 ppm on the whole citrus fruit. It was concluded that the
    residues on most fruit would not exceed 10 ppm. Table 2 gives results
    of assays for thiabendazole residues on citrus from the commercial
    packing houses taking part in the above trial (Anon., 1972).

    TABLE 2  Summary of assays for thiabendazole (TBZ) residues
             on citrus fruit1
    Experiment     Citrus              TBZ               TBZ residue
    (no.)          variety        concentration in       in the fruit
                   or species     the coating (ppm)      (ppm)2

    1              Valencia       6 2003                 4.7

    2              Valencia       6 000                  3.0

    3              Valencia       5 500                  4.8

    4              Grapefruit     6 4003                 3.3

    5              Lemon          6 000                  5.2

    6              Valencia       7 800                  7.4

    7              Navel          5 500                  9.0

    8              Lemon          7 7443                 7.4

    9              Lemon          7 9203                 7.1

    10             Navel          7 800                  5.6

    11             Navel          6 000                  5.1

    12             Lemon          6 000                  8.3

    13             Lemon          10 000                 5.2

    14             Lemon          12 000                 5.7

    1  Based on actual present practices of a selection of packing
       houses, and reflecting a highly variant usage pattern. Data
       obtained from fourteen commercial packinghouse trials
       conducted from 26/3/71 through 25/3/72.

    2  Average residue values of data obtained from 1-4 analytical
       laboratories involved in the study.

    3  Values obtained from actual analysis of coating samples, other
       values are calculated theoretical concentrations.

    The size, skin texture and species of citrus fruit influences the
    amount of wax coating, and hence the amount of thiabendazole,
    deposited on the skin. Equipment and method of application are also
    important. Table 3 indicates the effect of fruit size, species and
    concentration of thiabendazole on the level of the deposit on the
    fruit (Anon., 1972).

    TABLE 3  Effect of size and species on residues of thiabendazole (TBZ)
             on citrus fruits


                           Fruit                 Residue1
    % TBZ       Species    Size    Diameter      mg/kg            g/cm2
    in wax                 (gm)    (cm)

    0.3         Orange     180     5.6           3.24  1.25      3.33
                           138     6.1           3.45  1.45      3.68
                           113     6.6           2.75  0.78      3.06
                           88      7.2           2.59  1.03      3.29

                Lemon      200     5.1           3.45  1.35      3.57
                           140     5.6           3.06  1.41      3.03
                           115     6.1           3.65  0.52      3.67
                           95      6.5           3.63  0.22      4.22

    0.5         Orange     180     5.6           6.22  2.10      6.29
                           138     6.1           6.99  0.96      7.28
                           113     6.6           5.75  2.04      6.57
                           88      7.2           6.93  2.46      8.55

                Lemon      200     5.1           9.15  2.53      8.12
                           140     5.6           6.95  2.01      6.75
                           115     6.1           7.58  1.64      7.76
                           95      6.5           6.98  1.24      7.79

    1 Mean and standard deviation of six analyses.

    Oranges treated in South Africa with a wax emulsion containing 16 000
    ppm (1.6%) thiabendazole were analysed in the Netherlands to determine
    the degree of penetration of thiabendazole into edible portion. Table
    4 indicates that approximately 9% of the total is found in the edible
    portion with a level of approximately 1 ppm (Anon., 1972).

    TABLE 4  Thiabendazole (TBZ) residues in the edible portion
             of oranges treated with high doses1


    Fruit          TBZ residue         TBZ residue         TBZ residue
    (no.)          in whole            in peel (ppm)       in edible
                   fruit (ppm)                             portion (ppm)

    1              9.0                 34.3                1.16

    2              7.7                 26.6                1.19

    3              6.2                 25.0                0.63

    4              7.3                 23.8                0.99

    5              6.2                 19.1                0.83

    6              7.7                 26.0                0.39

    7              5.3                 22.4                0.74

    8              8 3                 35.4                0.84

    Mean           7.2                 26.6                0.85

    1  16 000 ppm thiabendazole brush on, FMC wax.

    In data submitted to the U.S. Environmental Protection Agency (Merck,
    Sharpe and Dohme Co., 1972) it was shown that the average
    concentration of thiabendazole in fresh orange juice (single strength)
    was 0.14 ppm when fruit with an average residue of 5.10 ppm was
    converted commercially into juice.

    The thiabendazole residue in dried citrus pulp prepared from unwashed
    fruit, previously treated with thiabendazole in wax so as to leave a
    residue of 10 ppm, is calculated to be 35 ppm. Fruit with a residue of
    5.10 ppm produced dried pulp containing 17.43 ppm thiabendazole. Dried
    citrus pulp is used for cattle feed at a rate not above 20% of the
    mixed ration. Studies reported earlier (FAO/WHO, 1971) indicate that
    when thiabendazole is fed to cattle at rates up to 20 ppm in the whole
    ration no detectable residues appear in the milk.


    New data were available for consideration by the Joint Meeting,
    including a statistical analysis of analytical data showing that many
    individual fruit will contain residues greatly in excess of 6 ppm when
    thiabendazole is used for the effective control of post harvest decay
    and for the suppression of sporulation. In view of the importance of
    finding alternatives to diphenyl for this purpose, the Meeting
    considered that the tolerance should be raised to provide for these
    higher residue levels. Due consideration was given to the data
    indicating that only a small proportion of the residue was in the pulp
    or would find its way into citrus fruit juice and other citrus


    The recommendation proposed in 1970 for a tolerance of 6 ppm
    thiabendazole on whole citrus fruit is amended as follows:

         Citrus fruit        10 ppm


    This tolerance applies to residue levels likely to be found in samples
    of all types of citrus fruit immediately following the application of
    thiabendazole in wax emulsion. Due to the stability of the deposit it
    is not expected that any significant change in residue level will
    occur during storage, shipment and distribution of citrus fruits.




    Anon. (1972) Joint submission by citrus industries of
    California - Arizona, Israel and South Africa and by Merck, Sharp and
    Dohme International to FAO. (unpublished)

    Eckert, J.W., and Kolbezen, K.J. (1971a) Chemical treatments for the
    control of post harvest diseases of citrus fruit. Proc. 6th British
    Insectic. Fungic. Conf., p.683 - 693.

    Eckert, J.W. and Kolbezen, M.J. (1971b) Effect of levels of
    thiabendazole residues on sporulation of Penicillium digitatum on
    citrus fruit. Report dated 11 June 1971, University of California,
    Riverside. (unpublished)

    FAO/WHO (1971) 1970 evaluations of some pesticide residues in food.
    FAO/AGP/1970/M/12/1; WHO/Food Add./71.42.

    FAO/WHO (1972) 1971 evaluations of some pesticide residues in food.
    (in press)

    Kruysse, A. (1971) The determination of an acceptable quality level of
    thiabendazole in citrus fruit and the selection of a standard sampling
    inspection plan. Paper submitted to the Ad Hoc Working Group, Codex
    Committee on Pesticide Residues, Copenhagen. CX/PR/WG 71/10 Add. 2.

    Merck, Sharp and Dohme Co. (1972) Petition to the U.S. Environmental
    Protection Agency for the establishment of tolerances for
    thiabendazole on citrus fruits (30/10/72).

    See Also:
       Toxicological Abbreviations
       Thiabendazole (WHO Food Additives Series 39)
       Thiabendazole (AGP:1970/M/12/1)
       Thiabendazole (WHO Pesticide Residues Series 1)
       Thiabendazole (WHO Pesticide Residues Series 5)
       Thiabendazole (Pesticide residues in food: 1977 evaluations)
       Thiabendazole (Pesticide residues in food: 1979 evaluations)
       Thiabendazole (Pesticide residues in food: 1981 evaluations)