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    PARATHION-METHYL      JMPR 1978

    Explanation

         Parathion-methyl was reviewed in 1968, 1972 and 1975 (FAO/WHO
    1969b, 1973b, 1976b). The 1975 Meeting required oral studies on
    teratogenesis and on reproduction in species appropriate to such
    tests to be carried out by 1978. In addition, the following
    information was considered desirable.

         1.   Adequate long-term studies in at least one
              mammalian species.

         2.   Information on current use patterns in various
              countries on crops for which no
              recommendations are made and on residue levels
              resulting from such uses.

         Some of the information has been submitted and is evaluated
    below.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Parathion-methyl is a general-purpose insecticide in several
    countries although it is slowly being replaced by the newer
    insecticides. Application is at 0.02 - 0.05% concentrations at
    rates of 350 g/ha to 1 kg/ha. The compound, being already a
    commodity product, is considered one of the more widely used
    insecticides world-wide. National use patterns, especially in
    tropical countries, are therefore still important.

    In Australia, specific uses include the following.

         1.   Orchard crops, Parathion-methyl is applied at concentrations
              of 20-50 g/100 l (0.02-0.05%) to control aphids, jassids,
              coddling moth, light brown apple moth, oriental fruit
              moth and scale insects with application being made
              throughout the season. A pre-harvest interval of 14 days
              is recommended.

         2.   Field and vegetable crops. Parathion-methyl is applied at 33
              33 g/100 l (0.03%) or at 350 g/ha to control aphids,
              bugs, caterpillars and mites. Application is made at
              10-14 days intervals or as required throughout the
              growing season. The pre-harvest interval is 14 days.

         3.   Cotton. Parathion-methyl is applied at 350-700 g/ha, in
              convenient concentrations, to control cluster
              caterpillars, loopers, aphids and mites. Applications are
              made when the pests are first seen. The pre-harvest
              interval is 14 days.

         4.   Tobacco. Application is at 52 g/100l (0.05%) in admixture
              with DDT (0.1%) to control budworms, leaf miners and
              loopers. It is applied weekly or as required.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

    In soybeans


         Soybeans treated with an emulsifiable formulation of
    Parathion-Methyl at 1.1 and 2.2 kg ai/ha in the United States in
    1968 showed no detectable residues of paraoxon-methyl,
    parathion-methyl or nitrophenol 16-37 days after the last
    application. Parathion-methyl residues were detected in beans plus
    pods with applications 1-14 days before harvest, but the oxon was
    not detected and p-nitrophenol was detected only at 1 day after
    application (Table 1).

    In soybean forage

         Residue determinations were conducted on field-treated samples
    of soybean forage from three locations in the United States. At 1.1
    kg ai/ha residues were below 1.0 mg/kg after 5 days. Residues of
    paraoxon-methyl could not be detected (< 0.05 mg/kg) while
    p-nitrophenol was generally below 0.2 mg/kg (Table 2).

    In cottonseed

         Residues were determined in field-treated samples of
    cottonseed from 12 locations. The detectable residues were below
    0.2 mg/kg paraoxon-methyl, parathion-methyl and p-nitrophenol in
    mature cottonseeds from cotton treated with emulsifiable
    formulations at rates up to and including 1.375 kg ai/ha. The
    interval between the last application and harvest ranged from 18 to
    74 days.

         ULV application of parathion-methyl at 0.83 kg/ha gave no
    detectable residues in the mature cottonseeds.

    In various crops in Finland

         The residues of parathion-methyl from supervised trials on
    several crops in Finland are shown in Table 3. Residues are
    generally low at the pre-harvest intervals adopted.

    In green beans

         Low-level residues were obtained in a recent series of residue
    trials in the Philippines. Insecticides were applied weekly at 1.0
    and 2.0 kg ai/ha two weeks after emergence; the latter is double
    the recommended rate. On the basis of the established MRL of 1
    mg/kg for vegetables in general, a two days pre-harvest interval
    may be adequate for tropical climates (Table 4).

    
    TABLE 1. Parathion-methyl and p-nitrophenol residues in field-treated soybeans
             in USA 1/, 2/

                                                                                   

                   Rate           Days after                 Residue, mg/kg
    Location       (kg ai/ha)     Application    Parathion-methyl    p-nitrophenol
                                                                                   

    Sweethome,
    Ark.           1.1            1              14.6                0.1
                                                 15.8                0.1

                   2.2            1              40.0                0.2
                                                 36.2                0.1

                   1.1            5              3.7                 ND2/
                                                 3.25                ND

                   2.2            5              6.0                 ND
                                                 5.8                 ND

                   1.1            7              1.9                 ND
                                                 2.2                 ND

                   2.2            7              2.7                 ND
                                                 2.6                 ND

                   1.1            14             1.1                 ND
                                                 1.1                 ND

                   2.2                           1.9                 ND
                                                 1.8                 ND

                   1.1            16             ND                  ND
                                                 ND                  ND

                   2.2                           ND                  ND
                                                 ND                  ND
                                                                                   

    1/ Paraoxon-methyl was sought in all samples but not detected.
    2/ Sample consists of bean plus pod.
    3/ ND =     < 0.02 mg/kg parathion-methyl
                < 0.05 mg/kg paraoxon-methyl
                < 0.05 mg/kg p-nitrophenol
     
        TABLE 2. Parathion-methyl and p-nitrophenol residues in field-treated soybean forage
             in USA 1/

                                                                                       

                        Rate           Days after                Residue, mg/kg
    Location            (kg ai/ha)     application    Parathion-methyl    p-nitrophenol
                                                                                       

    Stoneveille,
    Miss                  1.1               1         2.6, 2.8            0.2, 0.2
                          2.2                         6.2, 6.6            0.7, 0.6

                          1.1               5         0.5, 0.4            0.1, 0.1
                          2.2                         1.0, 1.1            0.2, 0.2

                          1.1               7         0.4, 0.4            0.1, 0.1
                          2.2                         0.8, 0.9            0.1, 0.1

                          1.1              14         0.3, 0.3            ND2/,0.1
                          2.2                         0.6, 0.6            Nd, 0.1

                          1.1              21         ND                  ND
                          2.2                         0.08,0.08           ND

    Charleston,
    Ill.                  1.1              17         ND                  ND
                          2.2                         ND                  ND

    Charleston,
    Ill. (dry forage)     1.1              22         0.03,0.02           ND
                          2.2                         0.03,0.03           ND

    Albany,
    Ga.                   1.1              19         ND                  ND
                          2.2                         ND                  ND
                                                                                       

    1/ Paraoxon-methyl was sought in all samples but not detected.
    2/ ND =     < 0.02 mg/kg parathion-methyl
                < 0.05 mg/kg paraoxon-methyl
                < 0.05 mg/kg p-nitrophenol
             TABLE 3. Residues of parathion-methyl from supervised trials in Finland

                                                                                         

    Crop             Rate and              Interval from            Residues, mg/kg
                     formulation           last application
                                           to harvest days
                                                                                         

    blackcurrant     1.0 g/bush, dust            22             washed           0.05
                                                                unwashed         0.05

    pea              150 g/ha, dust              29             pea         ND   (<0.05)
                                                                pod         ND   (<0.05)

    pea              150 g/ha, dust              22             pea         ND
                                                                pod         ND

    pea              150 g/ha, dust              15             pea         ND
                                                                pod         ND

    pea              150 g/ha, dust               8             pea         ND
                                                                pod         ND
    cauliflower      150 g/ha, dust              21             washed      ND   (<0.05)
                                                                unwashed    ND

    sugar beet       150 g/ha, dust              28             washed roots ND  (<0.03)
                                                                tops             0.09
    sugar beet       150 g/ha, dust              21             washed roots ND  (<0.03)
                                                                tops             0.6

    sugar beet       150 g/ha, dust               6             washed roots     0.04
                                                                tops             0.6

    cabbage          150 g/ha, dust              28             inner cabbage ND (< 0.05)
                                                                whole cabbage ND

    cabbage          150 g/ha, dust              21             inner cabbage ND
                                                                whole cabbage ND

    cabbage          150 g/ha, dust              14             inner cabbage    0.08
                                                                whole cabbage    0.08

    cabbage          150 g/ha, dust               7             inner cabbage    0.18
                                                                whole cabbage    0.18

    sugar beet       300 g/ha                     1                              0.5

    sugar beet       300 g/ha                     2                              0.34

    TABLE 3. (Cont'd.)

                                                                                         

    Crop             Rate and              Interval from            Residues, mg/kg
                     formulation           last application
                                           to harvest days
                                                                                         

    sugar beet       300 g/ha                     3                              0.15

    sugar beet       300 g/ha                     4                              0.12

    sugar beet       300 ha                       7                              0.04

    sugar beet       300 g/ha                     9                              0.04

    sugar beet       90 g/ha                    126             washed      ND   (<0.005)

    sugar beet       90 g/ha                    126             washed      ND

                                                                                         
    

        TABLE 4. Residues of parathion-methyl in green beans, Philippines 1978

                                                                                                  

                                       Residues (mg/kg) at intervals (days) after last application
    No. of    Application rate                                                                    
    trials    (kg ai/ha)
              emulsion concentrate     0         1         2         3         5         7
                                                                                                  

    2         1 kg ai/ha
               5                      1.30      0.39      0.13      0.02      ND =      ND =
                                                                               < 0.01    < 0.01

    2         2 kg ai/ha
               5                      2.53      1.07      0.57      0.06      ND        ND

                                                                                                  
    
         In cabbage

         No detectable residues (< 0.01 mg/kg) were observed with the
    recommended pre-harvest interval of 1 week.

    FATE OF RESIDUES

         No data were available.

    RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION

         In a market basket survey in 1970 in Australia, parathion-methyl
    residues were not determined specifically but the total
    organophosphorus (OP) residues found did not exceed 0.5 mg/kg in any
    of the foods examined. Some 240 samples were analysed and only 32
    contained any OP residues, of which only 3 exceeded 0.2 mg/kg.
    Residues of parathion methyl have occasionally been detected in
    vegetables sampled routinely in a continuous national residues survey
    programme. In general, these do not exceed 0.1 mg/kg. For example, in
    a 12 month period (1977-1978) 5 of 105 samples had residues higher
    then 0.1 mg/kg; these samples were localized and were indicative of
    applications in excess of the recommended rates.

         Market basket survey results from New Zealand are shown in Table
    5. Of 462 samples, only 30 contained parathion-methyl. All of the 5
    samples of leafy vegetables found positive had residues considerably
    lower than the established MRLs; but 11 citrus-fruit and one
    stone-fruit samples had residues at or about the MRL for fruits of
    0.2 mg/kg.

    NATIONAL MAXIMUM RESIDUE LIMITS REPORTED TO THE MEETING

         Australia reported national maximum residue limits as follows.

              Cottonseed, fruits, vegetables     1 mg/kg

              Cottonseed oil                     0.05 mg/kg

    APPRAISAL

         The 1975 Joint Meeting considered information desirable on
    current use patterns and residue levels in various countries on crops
    for which no recommendations had been made. Australia submitted data
    on use patterns on orchard crops, field and vegetable crops, cotton
    and tobacco. The pre-harvest interval is generally 14 days. Residue
    data were submitted by Monsanto Co. on soybeans, soybean forage and
    cottonseed and by Finland on a range of crops. Only low residues, if
    any could be detected 14 days after application. With cabbage and
    green beans under tropical conditions, degradation is rapid so that
    the established MRL is not likely to be exceeded with good agriculture
    practice.

        TABLE 5. Residues of parathion-methyl found in random sampling at the retail level
             in New Zealand

                                                                                      

    Year    Crop                  No. of      No. of
                                  sample      positive         Residues found (mg/kg)
                                  tested      samples        Range            Average
                                                                                      

    1970    Leafy vegetables        15            2          0.3              0.3

    1971    Leafy vegetables        54            1                           0.1

    1972    Leafy vegetables        48            0          -                -

    1973    Leafy vegetables        40            1          -                0.15

    1971    Root vegetables         48            0          -                -

    1972    Root vegetables         46            1                           0.26

    1973    Root vegetables         32            0

    1970    Pip fruit                             2          0.05             0.05

    1971    Pip fruit                9            3          0.04 - 0.02      0.03

    1972    Pip fruit               24            -          -                -

    1973    Pip fruit               27            0          -                -

    1972    Stone fruit             17            1                           0.25

    1971    Citrus                  18            4          0.5 - 0.01       0.2

    1972    citrus                  20            4          1.4 - 0.01       0.2

    1973    Citrus                  32            7          0.4 - 0.01       0.2

    1975    Fruit (fresh)           16            2          0.007 - 0.003    0.005

            Fruit (canned)          16            2          0.008 - 0.002    0.005
                                                                                      
             In two national residue survey programmes (in Australia and New
    Zealand), parathionmethyl has seldom been detected, and never at
    levels exceeding established MRLs.

    RECOMMENDATIONS

         No changes or additions to existing temporary MRLs are
    recommended.

    FURTHER WORK OR INFORMATION

    Desirable

    1.   Data on use patterns especially in tropical countries.

    REFERENCES

    Australia Report from the Codex Contact Point, Australia on
    (1978)              parathion-methyl.


    Conkin, R.A. Methyl parathion residue study. Contribution to the
    (1978)              FAO/WHO Joint Meeting on Pesticide Residue, Rome,
                        1978, by Monsanto Agricultural Products Co.,
                        U.S.A.

    Magallona, E.D. Report from the Codex Contact Point, Philippines,
    (1978)              on parathion-methyl.

    New Zealand Report from the Codex Contact Point, New Zealand, on
    (1978)              parathion-methyl.
    


    See Also:
       Toxicological Abbreviations
       Parathion-methyl (FAO/PL:1968/M/9/1)
       Parathion-methyl (WHO Pesticide Residues Series 2)
       Parathion-methyl (WHO Pesticide Residues Series 5)
       Parathion-methyl (Pesticide residues in food: 1979 evaluations)
       Parathion-methyl (Pesticide residues in food: 1980 evaluations)
       Parathion-methyl (Pesticide residues in food: 1984 evaluations)
       Parathion-methyl (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)