PESTICIDE RESIDUES IN FOOD - 1979


    Sponsored jointly by FAO and WHO






    EVALUATIONS 1979





    Joint meeting of the
    FAO Panel of Experts on Pesticide Residues
    in Food and the Environment
    and the
    WHO Expert Group on Pesticide Residues
    Geneva, 3-12 December 1979



    METHAMIDOPHOS

    Explanation

    This compound was evaluated in 1976.  The 1979 CCPR decided to ask the
    Meeting to re-evaluate the data because several delegations felt that
    the recommended MRLS were higher than necessary.  Comments on the
    significance of methamidophos as a residue from acephate application
    were also solicited.  This specifically relates to whether the MRLs
    for methamidophos would be exceeded from applications of acephate
    considering that in several crops, acephate has higher MRLs than
    methamidophos.

    RESIDUES IN FOOD AND THEIR EVALUATION

    The 1976 data on cauliflower, cucumber, eggplants and sugar beets are
    summarized in Table 1.  It is seen that there are enough grounds for
    lowering the MRLS for these commodities.

    In the case of alfalfa, soybeans and citrus fruit, the MRLs are
    necessary to take account of methamidophos residues as a result of
    acephate application since MRLS for acephate have been allocated for
    these crops. The data in 1976 for acephate can be used as the basis in
    this MRL.

    Table 1.   Residues from acephate and methamidophos application
               (from FAO/WHO 1977)

                                                                           
                         Acephate (mg/kg)              Methamidophos
                                                                  
                                     Based on                     Based on
    Commodity      Residues1    MRL    PHI     Residues2    MRL     PHI
                                      (days)                       (days)
                                                                           

    Cauliflower    2.3-4.4       5     14      0.5           2     14
    Cucumbers                    -             0.03-0.3      1      7
    Eggplants                    -             0.05-0.06     1      7
    Sugarbeets     n.d.-0.05     1     21      0.01(23)            21
                                               n.d. (28)
                                                                           

                   

    1  Combined acephate and methamidophos residues;
    2  No PHI recorded in 1976 but the values shown could be the basis
       for the recommended MRLs.

    From Table 1 the meeting was able to estimate the maximum residue
    levels which are likely to occur when methamidophos was used in
    practice and when the reported intervals between last application and
    harvest were observed.  Further, the 1976 data for acephate is
    sufficient to estimate maximum residue levels for methamidophos which
    could result from acephate application to alfalfa, citrus fruit and
    soybeans.  Additional data would be required if methamidophos are
    applied on these crops.

    RECOMMENDATIONS

    The following new Maximum Residue Limits are recommended:

                                                      
    Commodity        MRL         Preharvest intervals
                                    on which based
                                                      

    Alfalfa          2
    Cauliflower      1                    14
    Citrus           0.5
    Cucumber         0.5                   3
    Eggplant         0.1                  14
    Soybeans         0.05
    Sugarbeets       0.03
                                                      

    FURTHER WORK OR EVALUATION

    Desirable

    1.  Residue data on alfalfa, citrus and soybeans arising from the
        application of methamidophos;
    2.  Information on use patterns from countries where methamidophos is
        used;
    3.  Further information on the level and fate of residues during
        cooking and processing of fruit and vegetables.
    

    See Also:
       Toxicological Abbreviations
       Methamidophos (HSG 79, 1993)
       Methamidophos (ICSC)
       Methamidophos (JMPR Evaluations 2002 Part II Toxicological)
       Methamidophos (Pesticide residues in food: 1976 evaluations)
       Methamidophos (Pesticide residues in food: 1981 evaluations)
       Methamidophos (Pesticide residues in food: 1982 evaluations)
       Methamidophos (Pesticide residues in food: 1984 evaluations)
       Methamidophos (Pesticide residues in food: 1985 evaluations Part II Toxicology)
       Methamidophos (Pesticide residues in food: 1990 evaluations Toxicology)