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    CHLORPYRIPHOS

    Explanation

          This non-systemic organophosphorus insecticide was evaluated by
    the Joint Meeting in 1972 and an ADI of 0.0015 mg/kg/day was
    recommended (FAO/WHO, 1973). Tolerances were proposed for a number of
    foods of animal origin, fruits and vegetables for which residue data
    at that time were available. For commodities other than those listed,
    additional residue data from supervised trials were required before
    tolerances could be recommended. Since then, additional data on citrus
    fruits have become available.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

          Chlorpyriphos has been found active against the major citrus
    pest, Red Scale (Aonidiella aurantii), in some citrus growing areas,
    such as Australia, Mediterranean countries and South Africa. The
    citrus is often sprayed at in early stage of fruit development,
    although a practice of spraying until 1-2 months before harvest has
    developed in some countries, e.g. Israel and South Africa. No
    official, national registrations of such uses were known to the
    meeting.

    Pre-harvest treatments

          For general use, application rates of 25-100 g a.i./100 litre
    (using about 100 hl per ha) are recommended.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

    Residues in Citrus

          Table 1 summarizes the levels of chlorpyriphos residues found in
    and on citrus fruits in a series of supervised trials (Webb, 1974).
    Initial deposits ranging from about 0.2 - 1.3 mg/kg decrease gradually
    during the first months and then tend to level off. Within the
    recommended pre-harvest interval, residues do not exceed 0.25 mg/kg on
    a whole fruit basis.

          It is evident from the data in Table 2 that chlorpyriphos
    residues are largely concentrated in peel, and only a small proportion
    will penetrate into the inner, edible parts of fruits. Other data show
    that, with an occasional value as high as 0.1 mg/kg, most recorded
    residues in fruit flesh are below 0.05 mg/kg.

    
    TABLE 1.
    Residues of chlorpyriphos in citrus

                                                                                     

                        Application
    Country       a.i.                          Interval after     Residues,
      Fruit       concentration   rate          treatment,         mg/kg,
                  %               kg a.i./ha    months             in whole fruit
                                                                                     

    AUSTRALIA
    Oranges       0.025           1.7                  0           0.37-0.47
                                                       1           0.048-0.077
                                                       3           0.051-0.091
                                                       8           0.003-0.016
                  0.05            3.4                  8           0.018

    ITALY
    Oranges       0.06                                 0-1         0.14-0.17
                                                       1-2         0.10-0.15

    ISRAEL
    Oranges       0.048           4.8-5.8              6          0.07
                  0.072           7-2-8.6              6          0.11-0.16
                  0.096           9.6-11.5             6          0.11-0.19
                  0.048           8.6                  0           0.56
                                                       1           0.21
                                                       2           0.09
                  0.096           17.2                 0           1.34
                                                       1           0.25
                                                       2           0.15

    Grapefruit    0.048           8.6                  0           0.37
                                                       1           0.18
                                                       2          0.18
                  0.096           17.2                 0           0.57
                                                       1           0.24
                                                       2          0.22

    MOROCCO
    Clementines   0.048           1.9                  3           0.22
                  0.060           2.4                  5-6         0.03-0.04
                                                                                     
    
    TABLE 2.

    Chlorpyriphos distribution in citrus

                                                                            

                            Interval after    Chlorpyriphos residue, mg/kg
              Application     treatment,                             Whole
    Fruit       % a.i.          days          Flesh       Peel       fruit
                                                                            

    Oranges     0.06             15           <0.01       0.55       0.17
                                 30           <0.01       0.45       0.14
                                 45           <0.01       0.49       0.15
                                 60           <0.01       0.33       0.10

                                                                          


    APPRAISAL

          New data on chlorpyriphos residues in and on citrus fruits have
    been made available, meeting the requirement for supervised trials of
    an earlier Joint Meeting (FAO/WHO, 1973).

    RECOMMENDATIONS

          The following tolerance, additional to those of 1972, is
    recommended.

    TOLERANCE

                                mg/kg         Pre-harvest interval
                                              on which recommendation
                                              is based

    Citrus fruit (whole)        0.3           1 month

    REFERENCES

    FAO/WHO (1973). 1972 Evaluations on some pesticide residues in food.
    Report of the 1972 Joint Meeting of the FAO Working Party on Pesticide
    Residues and the WHO Expert Committee on Pesticide Residues, WHO
    techn. Rep. Ser., No. 525; FAO Agricultural Studies, No. 90.

    Webb, C. (1974). Request for a tolerance for chlorpyriphos in citrus
    fruit. Toxicology & Registration Section, Dow Chemical Company Ltd.,
    King's Lynn, Norfolk, U.K. (Unpublished)
    


    See Also:
       Toxicological Abbreviations