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    PESTICIDE RESIDUES IN FOOD - 1984


    Sponsored jointly by FAO and WHO






    EVALUATIONS 1984




    The monographs



    Data and recommendations of the joint meeting
    of the FAO Panel of Experts on Pesticide Residues
    in Food and the Environment and the
    WHO Expert Group on Pesticide Residues
    Rome, 24 September - 3 October 1984

    Food and Agriculture Organization of the United Nations
    Rome 1985

    PHORATE

    Explanation

         Phorate was evaluated by the Joint Meeting in 1977, 1982 and
    1983. 1/ Guideline levels were recorded in 1977. When a temporary ADI
    was established in 1982 these were converted to temporary MRLs.

         At the 16th Session of the CCPR, questions were raised on the
    limits for hops, lettuce, milk, peanuts and potatoes. Clarification of
    the commodity description "maize (green)" was also requested.

         The CCPR at its 14th Session asked the JMPR to consider amending
    the definition of the residue, currently "sum of phorate, its oxygen
    analogue, and their sulphoxides and sulphones, expressed as phorate",
    to exclude the oxygen analogue.

         The meeting received new information on uses of phorate, and
    results from supervised trials in South Africa on maize, potatoes and
    wheat.

         The new data are reviewed in this addendum, and the question of
    the CCPR are considered in the "Appraisal".

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Information has been provided from Canada and South Africa on
    approved uses of phorate (Table 1).

    RESIDUES RESULTING FROM SUPERVISED TRIALS

         Trials were carried on in South Africa on maize, potato and wheat
    plants (Table 2). Residues corresponding to good agricultural practice
    in South Africa are underlined. Residues were determined as the sum of
    phorate and its oxidised metabolites, expressed as phorate. The limit
    of determination for residues in maize and wheat was 0.05 mg/kg and in
    potatoes 0.1 mg/kg.

    Maize.  Residues were determined in the whole plant and in the cob
    (in the dough state). Residues were observed up to 32 days after
    treatment but none were detected in the plant or cob after the
    approved withholding period of 60 days.

    Potato.  Residues were observed 79 days after treatment, but not
    after the required withholding period (90 days).


              

    1/  See Annex 2 for FAO and WHO documentation.


        Table 1.  Approved uses of phorate

                                                                                                                      

    Country             Commodity      Approved application     Application                   Limitations
                                       rate. a.i.
                                                                                                                      

    Canada              Beans          1.1-2.25 kg/ha           Soil treatment in             At planting time
                                       (gran. 10-15%)           rows to the side              only. No feeding to
                                                                of the seeds                  animals within 60
                                                                                              days after treatment

                        Rutabaga       4.5 kg - 9.0 kg/ha       Soil treatment, band
                                       (gran. 10-15%)           5 cm below soil surface       At planting time only
                                                                or band spreading

                        Potato         2.25 kg - 3.25 kg/ha     Soil treatment in             - " -
                                       (gran. 10-15%)           furrows or bands on
                                                                each side of the row

                        Maize          0.55-1.1 kg/ha           Soil treatment in
                        (field and     (gran. 10-15%)           band placed 1-2.5 cm          - " -
                        sweet)                                  over seeds

                                       100 g/1000 m row         Band spraying                 - " -

                        Lettuce        1.1 kg/ha                Soil treatment in
                                       (gran. 10-15%)           band in sides of              - " -
                                                                the row

    South               Maize          5 g/100 m, plant row     Soil treatment in             At planting time only.
    Africa                             (gran. 10%)              planting furrow               Withholding period
                                                                                              60 days.

                        Potato         2-3 kg/ha                - " -                         At planting time only
                                       (gran. 10%)                                            Withholding period
                                                                                              90 days
                                                                                                                      

    Table 1.  (continued)

                                                                                                                      

    Country             Commodity      Approved application     Application                   Limitations
                                       rate. a.i.
                                                                                                                      

                        Cabbage        11-21 g/100 m            - " -                         At planting time only
                                       plant row                                              Withholding period
                                       (gran. 10%)                                            56 days

                        Wheat          3.5 g/100 ml             - " -                   )     At planting time only
                                       plant furrow                                     )     Withholding period
                                       (gran. 10%                                       )     90 days
                                                                                        )
                                       1.5 kg/ha                Soil treatment          )     No feeding to
                                       (gran. 10%               Overall treatment       )     animals
                                                                                                                      

    Table 2.  Residues of phorate from supervised trials in South Africa

                                                                                                                                            

    Crop                Application                Residue,mg/kg,at interval(days/after treatment (mean of duplicate determinations)
    (Location)          method and                                                                                                          
                        rate (a.i.)         0       10      20      30      40      50      60      70      80      90      100       110
                                                                                                                                            

    Maize               In planting furrow
    Leslie              at planting                 0.35    0.95           <0.02   <0.02           <0.02                   <0.02
                        Gran. 5 g/100m                                                                                     (cob)

    (Bethal)            10 g/100m           2.8             0.95            0.11    0.04           <0.02                   <0.02
                                                                                                                           (cob)
                        5 g/100m           <0.02           <0.02                                                           <0.02
                                                                                                                           (cob)

                        10 g/100m           0.06           <0.02                                                           <0.02
                                                                                                                           (cob)

    (Viljoenskroon)     5 g/100m                            0.35    <0.02                                                             <0.02
                                                                                                                                      (cob)

                        10 g/100m                           0.75    0.03                                                              <0.02
                                                                                                                                      (cob)

    Potato              In planting furrow
                        2 kg/ha                                            <0.1

                        3 kg/ha                                                                             0.15   <0.1

    Wheat               In planting furrow                 <0.05            0.9             0.09                   <0.05
    (plants)            1.66 g/100m

                        3.33 g/100m                         3.3             0.5            <0.05                   <0.05

                        6.66 g/100m                         4.4             7.0             1.6                     0.07
                                                                                                                                            
    

    Wheat (plants).  Residues were detected up to 42 days after
    treatment at the recommended dosage and up to 91 days at double
    dosage. No residue was observed at the approved dosage and 90-day
    withholding period.

    DEFINITION OF THE RESIDUE

         Almost all the data on which the residue evaluations were based
    were obtained after oxidation of all the components of the residue to
    the sulphone of the oxygen analogue. In the few cases where the
    compounds included in the definition were determined individually, all
    except the oxygen analogue have been detected. The transient existence
    of the oxygen analogue can be assumed.

         The analytical methods used to generate the residue data preclude
    an estimate of the proportions of the individual components
    contributing to the residue. Although it appears that the oxygen
    analogue could be excluded, its exclusion would not simplify the
    analytical procedure and could complicate the problems of enforcement
    in cases where the total residue found exceeds the MRL. It is
    concluded that the definition of the residue should not be changed.

    APPRAISAL

         New information on use patterns and on residues in maize,
    potatoes and wheat plants resulting from supervised trials was
    evaluated. No changes in previously estimated maximum residue levels
    in these crops were required.

         The 16th CCPR had asked the Joint Meeting to clarify the term
    "maize (green)". Since the original residues data referred to the
    whole maize plant, the commodity description should be changed to
    "maize fodder".

         It had been suggested at the 16th CCPR that neither the data made
    available to the 1977 JMPR on dried hops nor the analytical method
    used, supported a limit of 0.1 mg/kg. The meeting realized that, owing
    to the difficulties in the analysis of this crop, the limit of
    determination in the trials was about 0.2 mg/kg. An increase in the
    temporary MRL for dried hops to 0.2 mg/kg is therefore recommended.

         The meeting also reconsidered the data on peanuts and lettuce. As
    none of the data referred exactly to good agricultural practice in the
    countries in which the trails were performed, or adequate information
    on GAP in those countries was not available, the meeting was of the
    opinion that the proposed limits were the best estimates.

         It had been suggested that the limit for milk should be lowered
    from 0.05 to 0.02 mg/kg. As the limit of determination on which the
    trials were based was about 0.05 mg/kg, this is not possible.

         A delegation to the 16th CCPR was of the opinion that the limit
    for potatoes should be raised from 0.05 to 0.5 mg/kg, and that data
    submitted from the U.S.A. had not been taken into consideration by the
    1977 JMPR. The meeting reconsidered the original data and realized
    that the U.S.A. data had been taken into consideration, but only a few
    residues had been higher than 0.05 mg/kg. Furthermore, those data were
    old and residues had been determined by the cholinesterase-inhibition
    method, while all new data based on analysis by GLC, including the
    data supplied to this meeting from South Africa, showed residues well
    below 0.05 mg/kg. For these reasons the meeting maintained its
    original estimate.

         The possibility of simplifying the residue definition was
    considered. The analytical methods normally used involve converting
    the residue to the sulphone of the oxygen analogue and preclude an
    estimate of the proportions of the individual components contributing
    to the residue. When, exceptionally, the residue components have been
    separately determined, all except the oxygen analogue have been found.
    Although it appears that the oxygen analogue could be excluded, its
    exclusion would not simplify the analytical procedure and could
    complicate the problems of enforcement in cases where the total
    residue found exceeds the MRL. It is concluded that the definition of
    the residue should not be changed.

    RECOMMENDATIONS

         The following maximum residue levels were estimated and
    recommended as suitable for use as temporary MRLs.

                                                             

    Commodity                     TMRL, mg/kg
                                                             

    maize fodder                  0.05 (no change in TMRL)
    (description changed from
    "maize (green)"

    hops, dried                   0.2 (increased from 0.1)
                                                             

         It is recommended that the definition of the residue should not
    be changed.


    See Also:
       Toxicological Abbreviations
       Phorate (ICSC)
       Phorate (Pesticide residues in food: 1977 evaluations)
       Phorate (Pesticide residues in food: 1982 evaluations)
       Phorate (Pesticide residues in food: 1985 evaluations Part II Toxicology)
       Phorate (Pesticide residues in food: 1994 evaluations Part II Toxicology)
       Phorate (Pesticide residues in food: 1996 evaluations Part II Toxicological)