FENAMIPHOS            JMPR 1977


    Arising out of the list of requirements for further work or
    information published in the Report of the 1974 Joint Meeting
    (FAO/WHO, 1975a) some data on residues of fenamiphos in oranges and
    potatoes wore referred to the FAO Panel of &ports; reports of a very
    limited number of analyses of snap beans, broccoli, carrots, kiwifruit
    and tomatoes were also received but these added nothing of value to
    the data already available (FAO/WHO, 1975b). Some further information
    on the metabolism of fenamiphos in bean plants and on its uptake from
    soils was also made available to the Meeting.



    The residues of fenamiphos, together with its sulphoxide and sulphone,
    resulting from supervised trials on oranges and potatoes (Anonymous,
    1977) are shown in Table 1. Residues in potatoes were generally below
    0.2 mg/kg. In oranges, observed levels were mostly between 0.6 and 2.6
    mg/kg in the peel and between 0.01 and 0.25 mg/kg in the flesh of the
    fruit. These figures would correspond to a maximum of about 0.7 mg/kg
    in the whole fruit, most being below 0.5 mg/kg. No further data on
    other citrus fruits was available to the Meeting. Table 2 lists the
    limited data provided on residues in other crops (Anonymous, 1977).


    In plants

    Waggoner (1972) indicated the presence of two unidentified
    organosoluble metabolites (IV and V) of fenamiphos isolated from
    treated plant products. Work by Pither and Gronberg (1977) on the
    characterisation of these compounds has now been reported. Bean plants
    were treated, by stem injection or solution uptake, with various
    combinations of fenamiphos labelled with tritium or carbon-14 in
    various positions and the metabolites were isolated. Metabolite IV was
    identified as des-isopropyl fenamiphos sulphoxide; metabolite V was
    shown to contain the ethyl-O-P-O-ring structural backbone but the
    presence or absence of the isopropyl-N-P moiety could not be
    determined. Observed concentrations of these transient metabolites
    (0.6-3.8% metabolite IV and 0-0.7% metabolite V) confirmed those
    previously reported. These metabolites contribute little to the total
    residue which comprises mainly fenamiphos, fenamiphos sulphoxide,
    fenamiphos sulphone and some hydrolysis products.

        TABLE 1. Residues of fenamiphos resulting from supervised trials (oranges and potatoes)

                                                                rate                Interval            Residues2/found
    Crop            Country             Formulation1/       (kg a.i./ha)        (days)(mg/kg)
                                                                                                    Fruit Peel          Flesh

    Oranges (       USA                 15% G               100                 0                   <0.01               <0.01
            (                                                                   27                  <0.01               <0.01
            (                                                                   33                  <0.01               <0.01
            (                                                                   61                  1.50                0.02
            (                                                                   90                  1.66                0.07
            (                                                                   118                 1.78                0.13
            (                                                                   153                 1.65                0.04
            (                                                                   159                 1.56                <0.01
            (                                                                   189                 2.60                0.25
            (                                                                   194                 1.52                0.03
            (                                                                   215                 1.57                0.03
            (                                                                   238                 0.85                0.03
            (                                                                   456                 0.78                0.02
            (                                                                   483                 0.87                0.02
            (                                                                   513                 0.63                0.01

            (       Spain               5% G                10                  97                           0.17
            (                                                                   104                          0.12
            (                                                                   111                          0.06
            (                                                                   118                          0.04

    Potatoes(       Netherlands         5% G                10                  107                          0.15
            (                                                                   137                          0.12
            (                           40% EC              10                  107                          0.06
            (                                                                   137                          0.05

    TABLE 1. (Continued)

                                                                rate                Interval            Residues2/found
    Crop            Country             Formulation1/       (kg a.i./ha)        (days)(mg/kg)
                                                                                                    Fruit Peel          Flesh

            (       Federal Republic    40% EC              8                   153                          0.02
            (       of Germany                              8                   157                          0.08
            (                                               8                   146                          0.22
            (                                               10                  159                          0.07
            (                                               8                   159                          0.02
            (                                               6                   159                          0.03
            (                                               10                  156                          <0.01
            (                                               8                   156                          0.06
            (                                               6                   156                          0.05
            (                                               10                  133                          0.05
            (                                               10                  163                          0.01

    1/ G = granules; EC = emulsifiable concentrate.
    2/ Residues comprise fenamiphos, its sulphoxide and sulphone, determined. and expressed as fenamiphos sulphone.

    TABLE 2. Residues of fenamiphos resulting from supervised trials (miscellaneous)

                                                        rate              Interval       Residues2/found
    Crop                Country        Formulation1/    (kg a.i./ha)      (days)         (mg/kg)
    Beans               USA            3% SC            6.7               411            < 0.01
    (Snap)                                                                431            < 0.01

    Broccoli            USA            15% G            10                112            0.03

    Carrots             N. Zealand     -                8                 76             0.03
                                                                          98             <0.01
                                       -                12                76             0.05
                                                                          98             <0.01

    Kiwifruit           N. Zealand                      8                 185            <0.01
                                                        16                185            <0.01

    Tomatoes            N. Zealand     40% EC           8                 97             <0.01

    1/ SC = spraying concentrate; G = granules; EC = emulsifiable concentrate.
    2/ Residues comprise fenamiphos, its sulphoxide and sulphone, determined
       and expressed as fenamiphos sulphone.


    In soils

    The persistence of fenamiphos in soil and its uptake by certain crops
    was investigated by Shaw (1975). Technical fenamiphos was mixed with
    fenamiphos labelled with tritium in the S-CH3 position and with
    fenamiphos uniformly labelled with carbon-14 in the ring. The effects
    of plant growth and time on fenamiphos residues in soil treated with
    this doubly labelled material were studied. Corn and cotton were grown
    in the treated soil and harvested. After the soil had lain fallow, com
    and soybeans were grown in the treated soil, a portion of which had
    been extracted with methanol/water, and subsequently harvested. The
    tritium/carbon-14 ration of 4:1 was consistent throughout the study
    indicating no hydrolysis of the methylthio group from the ring

    Fenamiphos - 14C, 3H-treated soils contained 47% of the
    radioactivity as residue when the initial corn and cotton plants were
    harvested. The quantity of absorbed material was four times greater in
    corn plants (20%) than in cotton plants (5%). Soils still contained
    29% of the original radioactivity (18.5% was bound) one year after
    treatment. Rotational crops of soybeans and cotton, grown in extracted
    and non-extracted soils, took up less than 1.2% and 0.17% respectively
    of the applied material. No significant difference in residue uptake
    was detected between plants from in extracted or non-extracted soil. A
    difference in residue uptake clue to a plant species difference was
    detectable because cotton absorbs less fenamiphos residues than do
    corn or soybeans.


    National tolerances and associated pre-harvest intervals reported to
    the Meeting are shown in Table 3.

        TABLE 3. National tolerances reported to the Meeting


                                                           Tolerance        Pre-harvest
    Country              Commodity                         (mg/kg)          interval (days)

    Australia            Tomatoes, brassicas,
                         cucurbits, lettuce, citrus        0.05
                         pineapples, grapes,
                         bananas, ginger

    Federal Republic     Potatoes, tomatoes                0.2
    of Germany           Bananas (with peel), raw
                         coffee, grapes                    0.1

    TABLE 3. (Continued)


                                                           Tolerance        Pre-harvest
    Country              Commodity                         (mg/kg)          interval (days)

                         Other food of plant
                         origin                            0.05

    South Africa         General                           0.1
                         Potatoes                                           42

    Spain                General                                            60

    USA                  Bananas, Brussels sprouts,
                         cabbage                           0.1
                         Cottonseed                        0.05
                         Peanuts                           0.02
                         Peanut hulls                      0.4
                         Soybeans                          0.05


    Residues of fenamiphos observed in potatoes were generally below the
    level of 0.2 mg/kg and the new data were in accord with those
    previously available. For oranges, however, the latest data conflicted
    appreciably with those for a number of citrus fruits in 1974. Up to
    2.6 mg/kg was observed in the peel and up to 0.25 mg/kg in the flesh
    of the fruit; the maximum corresponds to about 0.7 mg/kg on the whole
    fruit, but the majority of results would be less than 0.5 mg/kg. These
    levels are an order of magnitude higher than the previously reported
    maxima of 0.3 mg/kg (peel) and 0.03 mg/kg (flesh) for tangerines;
    residues on grapefruit, lemons, limes and oranges were previously
    reported at levels at or only slightly above the limit of
    determination. Limited data on residues in other crops added nothing
    of value to those previously available. Further observations have
    helped to clarify the fate of residues in plants and soil.


    The recommendation for potatoes made by the 1974 Meeting is confirmed
    as no longer being temporary. The previous recommendation for citrus
    fruits is withdrawl and replaced by a maximum residue limit for
    oranges and a temporary maximum residue limit for other citrus fruits.
    The other recommendations remain unchanged.

    The following limits refer to the sum of fenamiphos, its sulphoxide
    and its sulphone, expressed as fenamiphos.

    Maximum residue limits

         Commodity                Limit, mg/kg
         Oranges, whole fruit     0.5
           flesh of fruit         0.1
         Potatoes                 0.2

    Temporary maximum residue limit

         Commodity                Limit, mg/kg
         Citrus fruits
         (other than oranges),
           whole fruit            0.05*

    * At or about the limit of determination.


    REQUIRED (by 1980)

    Further data on which to assess the residues in or on citrus fruits
    other than oranges and on tomatoes.


    1. Information on brain cholinesterase and behavioural studies in
    animals exposed to low levels for extended periods.

    2. Observations in humans.

    3. Additional studies on the potentiation effects with other
    organophosphorus pesticides.

    4. Residue data for raw agricultural products moving in commerce.

    5. Further residue data for different crops from supervised trials,
    especially for beans, cucumbers, lettuce, peppers and strawberries.


    Anonymous. (1977) Data on residues of fenamiphos in oranges, potatoes
    and other crops. Submitted by Bayer A.G. (Unpublished).

    Pither K.M. and Granberg, R.R. (1977) The metabolism of (R) Nemacur in
    plants. Chemagro Report No. 52257. (Unpublished).

    Shaw II, H.R. (1975) Determination of soil-borne residues and uptake
    by rotational crops from soil treated with (R)Nemacur. Chernagro
    Report No. 44226. (Unpublished).

    Waggoner, T.B. (1972) Metabolism of Nemacur (ethyl 4-(methylthio)-m-
    olyl isopropylphosphoramidate) and identification of two metabolites
    in plants. J. Agr. Food Chem., 20 (l): 157-160-

    FAO/WHO (1975a) 1974 evaluations of some pesticide residues in food.
    FAO/AGP/1974/M/11; WHO Pesticide Residue Series No. 4.

    FAO/WHO (1975b) Pesticide residues in foods Report of the 1974 Joint
    FAO/WHO Meeting. FAO Agricultural Studies No. 97; Wld. Hlth. Org. 
    techn. Rep. Ser., No. 574. WHO Technical Reports Series.

    See Also:
       Toxicological Abbreviations
       Fenamiphos (ICSC)
       Fenamiphos (WHO Pesticide Residues Series 4)
       Fenamiphos (Pesticide residues in food: 1978 evaluations)
       Fenamiphos (Pesticide residues in food: 1980 evaluations)
       Fenamiphos (Pesticide residues in food: 1985 evaluations Part II Toxicology)
       Fenamiphos (Pesticide residues in food: 1987 evaluations Part II Toxicology)
       Fenamiphos (Pesticide residues in food: 1997 evaluations Part II Toxicological & Environmental)
       Fenamiphos (JMPR Evaluations 2002 Part II Toxicological)