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    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



    FENITROTHION

    Explanation

    Fenitrothion was evaluated in 1969, 1974, 1976 and 1977.

    At its 11th Session, the CCPR requested the meeting to provide a
    recommendation for bran (processed) on the basis of new data known to
    be available: also for clarification of proposals for MRLs in pears
    and peaches as indicated in paragraphs 107 and 108 of ALINORM 79/24. 
    Further data on the use and fate of fenitrothion was also made
    available to the meeting by Australia.

    RESIDUES IN FOOD AND THEIR EVALUATION

    RESIDUES RESULTING FROM SUPERVISED TRIALS

    Pre-harvest

    Having examined the raw data from which a selection was made for
    presentation in Table 6 of the 1974 monograph, the meeting agreed that
    although the residues in pears appeared to be somewhat lower than
    those in apples in the trials carried out in Japan, the differences
    were small and probably not representative of the true picture
    world-wide.  It was agreed that the MRL for pears should be brought
    into line with that for apples.

    The meeting re-examined the raw data from 12 trials carried out on
    peaches in Japan and which provide the basis for the information
    contained in Table 6 of the 1974 monograph.  The original data were
    developed by analysis made separately on pulp and peel as is the
    custom in Japan.  The ratio of the weight of pulp to peel averaged
    90:10 (range 92/8-85/15).  Recalculation of the residue level on the
    whole fruit indicated that the bulk of the values fall below 1 mg/kg.

    Residues in Bran

    In 1974 and 1976 the meeting reviewed the use of fenitrothion for the
    protection of raw grain against stored-product pests.  Among the
    information reviewed were studies on the fate of fenitrothion residue,
    on grain subjected to milling and processing.  These data (FAO/WHO
    1975b page 266, 1977b page 369) showed that the bulk of the
    insecticide deposited on the grain remains in the epidermis and is
    removed from the bran during milling.

    Further studies by Desmarchelier (1979) with fenitrothion and eleven
    other grain protectant insecticides, showed that the concentration on
    the bran is from 2 to 3.2 times the concentration on the whole wheat. 
    Except for bioresmethrin and pirimiphosmethyl, where the concentration
    is 3.2 and 2.9 times that on raw grain respectively, all of the other
    insecticides tests including fenitrothion residue level all show a
    concentrating effect from 2 to 2.7 by comparison with the whole wheat.

    This figure depends to a small extent on the original rate of
    application of the insecticide and the time in storage prior to
    milling.  Generally the amount of insecticide in the flour is 10% or
    less of the concentration on the whole wheat.

    Desmarchelier (1979) extended his studies to determine the percentage
    loss of residues during processing of bran using a laboratory
    technique to simulate the least severe industrial process.  This
    consisted of heating the moistened bran for two hours at 90C.  He
    showed that 42% of the fenitrothion was lost from raw bran by such
    treatment.  With some other insecticides the loss was a high at 96%. 
    None of the insecticides was less subject to degradation than
    fenitrothion.

    Murray and Snelson (1978) studied the distribution of fenitrothion and
    bioresmethrin residues on mill fractions from wheat processed through
    a commercial flour mill.  The results of their investigations are set
    out in Table 1.  These show that the bran from all milling streams
    when blended together, contained fenitrothion residues 1.5 times as
    high as those present in raw wheat received into the mill.  Snelson
    (1979) also reports the results of monitoring 13 flour mills
    processing wheat containing from 5 to 10 mg/kg of fenitrothion.  The
    results, given in Table 2, indicate that 100% of the bran samples
    contained less than 20 mg/kg but up to 90% contained up to 15 mg/kg. 
    Only 23% of the bran samples contained less than 10 mg/kg.  These
    results are contrasted with the residues found in processed bran.

    There is no wheat available in Australia without residues of grain
    protestant insecticides.  It was concluded that processed bran
    available retail would reflect the effect of processing on the
    residues present in raw bran.  A survey was conducted in Australia
    (Snelson 1979) in which 36 samples of processed bran representing 12
    different commercial products available in retail stores of three
    cities, located over a distance of 2,000 kilometres were analysed.  In
    spite of the fact that all raw bran available for processing contained
    fenitrothion to a limit of 20 mg/kg, it was found that 80% of the
    processed bran available in the form of breakfast cereals contained
    less than 1 mg/kg of fenitrothion residue.  8% of the samples
    contained more than 3 mg/kg but these (3) represented products which
    were only partially processed.  36% of the samples contained no
    detectable residues (less than 0.1 mg/kg) of fenitrothion.

    In the light of the results of the above survey, a supervised trial
    was carried out in a factory processing three bran products.  The
    results of the trial are shown in Table 3.  These indicate that
    substantially all of the fenitrothion residues are destroyed in the
    cooking process which involves prolonged heating under pressure with
    live steam after the bran has been subjected to wet digestion with
    malt.  The subsequent drying, extrusion, drying and toasting are all
    vigorous processes employing high temperatures that would be expected
    to destroy any residues which were not destroyed during the cooking. 
    The trial confirmed that normal commercial processing destroyed the
    bulk of the residues.



        Table 1. Residues of Fenitrothion, Mg/kg, in Wheat Milling Fractions (and of Bioresmethrin)

                                                                                               
    Sample No.                          Treated with 12 mg/kg               Treated at harvest
    and                                 fenitrothion (plus 1 mg/kg            with 12 mg/kg
    Description                         syngergized bioresmethrin)            fenitrothion
                                       Laboratory A      Laboratory B         Laboratory A
                                                                                               

     1. Wheat before point
        of pesticide application           <0.5            -                       N.A.

     2. Wheat when received
        into the mill                      8               7  (0.7)                7

     3. Wheat at first break roll
        before it enters the rolls         4               4  (0.6)                3

     4. Crushed wheat at first
        break roll after it drops          5               4  (0.6)                3
        from the rolls

     5. Flour sieved from the
        sitter fed from first              1               0.8 (<0.05)             1
        break roll (clean stream)

     6. Flour sieved from the
        sitter fed by the last
        break roll (dirty stream)          4               3  (0.1)                2

     7. Flour sieved from the
        sitter fed by the first
        reduction roll (clean stream)      0.5             0.6  (<0.05)            0.5

     8. Flour sieved from the
        sitter fed by the last
        reduction roll (dirty stream)      5               5  (0.3)                4
                                                                                               

    Table 1.  Continued...

                                                                                               
    Sample No.                          Treated with 12 mg/kg               Treated at harvest
    and                                 fenitrothion (plus 1 mg/kg            with 12 mg/kg
    Description                         syngergized bioresmethrin)            fenitrothion
                                       Laboratory A      Laboratory B         Laboratory A
                                                                                               

     9.  Flour from all streams,
         being fed into bulk flour
         bins or into packers              2               2  (0.1)                1

    10.  pollard from all streams
         before it is mixed with
         the bran                          6               8  (0.7)                7

    11.  Bran from all streams
         before it is mixed with the
         pollard                           12              11  (1)                 11

    12. Wheat germ                         10              10  (2)                  7
                                                                                               

    Figures in ( ) are for bioresmethrin.
    


    Table 2.  Fenitrothion Residues on Raw and Processed Bran
              (Results from Australian Survey)

                                                               
           Raw Bran                       Processed Bran
    Range of    No.    %           Range of      No.      %
    Residues                       Residues
                                                               

     <10         3      23          <0.1         13       36
    10-12        5      38         0-1-0.5        7       19
    12-14        1       8         6.5-1.0        9       25
    14-16        3      23         1.0-2.0        3        8
    16-18        0       0         2.0-3.0        1        3
    18-20        1       8         >3.0**         3        8
                                                              
                13     100                       36**     100
                                                               

    *  Maximum 4.0
    ** 12 different brands.


    Table 3.  Effect of Commercial Processing on Fenitrothion
              Residues on Bran

                                                                        
    Processing Stage               Product A       Product B   Product C
                                   Rep.
                                     1      2      1      2    1      2
                                                                        

    1. Raw bran before cooking      5       4      3      4     23     21

    2. Cooked bran taken
       directly from cookers       <0.05  <0.05  <0.05  <0.05   2      2

    3. Bran taken after initial
       drying stage                <0.05  <0.05  <0.05  <0.05   1      2

    4. Finished product taken
       after bran has been formed
       into final shape and dried/
       toasted through an oven        1   <0.05  <0.05  <0.05   1      1
                                                                        


    Tempone (1979) has shown that fenitrothion and other grain protectant
    insecticides are destroyed during the melting process when grain
    protectant insecticide residues are present on the raw barley.  These
    investigations have been verified by extensive surveys in which malt
    from more than 30 maltsters has been monitored for fenitrothion and
    other insecticide residues.  It was already known that all of the
    barley available for melting contained either malathion or
    fenitrothion residues at levels up to the maximum residue limits (8
    and 10 mg/kg respectively).  None of the 36 samples examined contained
    fenitrothion residues at or above the limit of reporting (0.1 mg/kg). 
    (Snelson, 1979).  It is apparent therefore, that the melting process
    effectively destroys a variety of insecticide residues and no doubt
    the enzymes of malt which is added to the process to improve the
    palatability and flavour of the bran, could contribute to the
    destruction of fenitrothion prior to and during the cooking of raw
    bran.

    Residues in Flour

    Snelson (1979) observed that commercial flour mills could not comply
    with the national residue limit for fenitrothion in flour (1 mg/kg)
    particularly when wheat available had been treated within the previous
    two to three months with fenitrothion at the recommended level of 6
    mg/kg.  The matter was investigated by Murray and Snelson (1978) and
    the results, summarised in Table 1, indicate that although the flour
    sieved from the sifter fed by the first reduction rolls contains
    residues of the order of 0.5 mg/kg, this is later blended with flour
    from other streams containing slightly higher residues of fenitrothion
    due to the higher degree of extraction which occurs in these steps. 
    As a consequence, the commercial flour contained 2 mg/kg of
    fenitrothion.

    All of the data examined by the meeting in 1974 and 1976 came from
    experimental milling equipment which, although designed to reproduce
    commercial practice, does not give the same high degree of extraction. 
    In view of the extensive commercial experience which shows that
    commercial flour mills cannot comply with the maximum residue limit of
    1 mg/kg, the meeting recommended that the maximum residue limit in
    flour be raised to 3 mg/kg.

    Desmarchelier (1979a) and Desmarchelier and Marsden (1979) thoroughly
    investigated the transfer of fenitrothion residues from wheat via
    flour into wheat gluten and the fate of these residues during the
    cooking of many varieties of bread prepared from different recipes. 
    They showed that although gluten represents approximately 10% of the
    content of raw grain, the residue in the extracted gluten is about 30%
    of that present in the raw grain, thus representing a threefold
    concentration above the expected level.  This picture is not unique to
    fenitrothion, but appears to occur with many insecticides of quite
    different chemical groups.

    These investigations showed that irrespective of the level of residues
    in the flour or in gluten and independent of the type of bread, the
    recipe or the baking process, approximately 50% of the residue was
    destroyed in the process.

    Likewise, the processing of oats for the production of rolled oats,
    involving as it does the removal of the hulls and the heating of the
    kernel to produce groats, in the removal and destruction of
    substantially all the insecticide deposited on the grain for
    protection against stored product pests.  Fenitrothion is removed in
    this operation to an extent exceeding 95% (Desmarchelier, 1979).

    APPRAISAL

    New information has been made available concerning the level and fate
    of fenitrothion residues on bran and other foods processed from raw
    cereals.  The meeting recognised that when fenitrothion was used to
    protect grain from stored product pests the bulk of the insecticide is
    deposited on the epidermis and is removed on the bran during the
    milling process.  The concentration on the bran is from 2 to 2.5 times
    that on the whole wheat.

    Although some raw, unprocessed bran is marketed for direct consumption
    or for culinary purposes, the bulk of the bran used for human
    consumption is first subjected to processes designed to improve the
    flavour and palatability.  These processes subject raw bran to
    vigorous physical and chemical processes which destroy substantially
    all of the fenitrothion residues present.  The available data indicate
    that a maximum residue could be established at a lower level on
    processed bran to assist food processors and food control officials in
    their monitoring activities.

    It has been shown that the malting process destroys substantially all
    of the fenitrothion present on the raw barley.  Likewise the removal
    of the hulls from raw oats and the process involved in converting the
    hulled oats into groats and rolled oats destroys substantially more
    than 95% of the residues present on the raw oats.

    The meeting has reviewed the data on fenitrothion residues on peaches
    and pears and agrees there is justification for amending the
    recommendations previously made.

    RECOMMENDATION

    The following additional maximum residue limits are recommended:
    Wheat bran (processed) 2 mg/kg.

    The maximum residue limits previously proposed are amended as follows:

    Wheat bran to read wheat bran (raw)    20
    Pears                                   0.5 mg/kg
    Peaches                                 1 mg/kg
    Wheat flour (white)                     3 mg/kg

    REFERENCES

    Desmarchelier, J.M. - The effect of milling and processing on the
    level and fate of grain protectant insecticide residues on wheat and
    oats. Report of CSIRO Division of Entomology, Canberra, Australia, May
    1979.

      Transfer of grain protectant insecticide residues from grain to
    wheat gluten.  Report of CSIRO Division of Entomology, Canberra,
    Australia, June 1979.

    Desmarchelier, J.M. and Marsden, P. - Effect of baking on fenitrothion
    residues in wheat gluten.  Report of CSIRO Division of Entomology,
    Canberra, Australia, May 1979.

    Murray, D. and Snelson, J.T. - Fenitrothion and bioresmethrin residues
    in milled products from a commercial flour mill. Report to Department
    of Primary Industry, Canberra, June 1978.

    Snelson. J.T. Pesticide Residue Survey, Department of Primary
    Industry, Canberra, July 1979.

      The effect of processing on fenitrothion residues on raw bran.
    Report to Department of Primary Industry, Canberra, October 1979.

    Tempone, M.J. Studies on the effects of insecticides on barley
    malting, Government of Victoria. Research Project Series No. 50,
    January, 1979.
    


    See Also:
       Toxicological Abbreviations
       Fenitrothion (EHC 133, 1992)
       Fenitrothion (HSG 65, 1991)
       Fenitrothion (ICSC)
       Fenitrothion (PDS)
       Fenitrothion (FAO/PL:1969/M/17/1)
       Fenitrothion (WHO Pesticide Residues Series 4)
       Fenitrothion (Pesticide residues in food: 1976 evaluations)
       Fenitrothion (Pesticide residues in food: 1977 evaluations)
       Fenitrothion (Pesticide residues in food: 1982 evaluations)
       Fenitrothion (Pesticide residues in food: 1983 evaluations)
       Fenitrothion (Pesticide residues in food: 1984 evaluations)
       Fenitrothion (Pesticide residues in food: 1986 evaluations Part II Toxicology)
       Fenitrothion (Pesticide residues in food: 1988 evaluations Part II Toxicology)
       Fenitrothion (JMPR Evaluations 2000 Part II Toxicological)