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    BROMOPHOS        JMPR 1975

    Explanation

         When reviewing the recommendations of the 1972 JMPR, the Codex
    Committee on Pesticide Residues at its 8th Session (CCPR, 1975) asked
    for information on residues of the bromophos metabolite
    2,5-dichloro-4-bromophenol, which is also a metabolite of
    bromophos-ethyl and other compounds, and whether this metabolite
    should be included in the proposed tolerances (para. 34, CCPR, 1975).
    The Joint Meeting was also asked:

         (1) to reconsider the residue data reported in the 1972 Monograph
         and to indicate the pre-harvest intervals, rates of application,
         etc., on which the recommendations were based (para. 35);

         (2) to recommend maximum residue limits for peanuts and tropical
         grains (para. 35), and to reconsider the limit for red currants
         (para. 36);

         (3) to consider the possible occurrence of residues in milk and
         meat of cattle arising from bromophos residues up to 2 mg/kg in
         sugar beet leaves and 0.5 mg/kg in sugar beet roots (para. 38);

         (4) to establish limits for residues in milk products in addition
         to the existing limits for milk, and for Brussels sprouts and
         broad beans (para. 40).

         Some information on residues of bromophos in Brussels sprouts
    (pre-harvest treatment) had been supplied to the Meeting and was
    considered. New data relating to usage on stored grain and to the fate
    of residues on storage and processing, that had been included amongst
    the requirements listed in the monograph of the 1972 meeting were also
    reviewed.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

    Pre-harvest treatment

         Residue data in Brussels sprouts for the raw agricultural
    commodity (RIV, 1967) and after cleaning, washing and cooking (RIV,
    1974) have become available from the Netherlands. Details are given in
    Table 1.

    TABLE 1. Bromophos residues in Brussels sprouts

                                                                           

                                        Residue mg/kg after interval (days)
                                                                           
    Application
        No.         Rate (kg/ha)           7            14           21
                                                                           

        2-3           0.6-0.7                         0.01          0.01

        1             0.7              0.2-0.3a       0.1-0.2a

        1             0.7              0.04-0.07b     <0.04b

        1             0.7              <0.04c         <0.04c
                                                                           

    a Ready for marketing.

    b After cleaning and washing.

    c After cleaning, washing and cooking.


    Post-harvest treatment

         In a test reported from South Africa, maize and sorghum were
    sprayed with bromophos at different concentrations (EC) on a conveyer
    belt or on the flowing grain stream (Dep. Agr. Techn. Serv., 1975).
    The results are summarized in Table 2. It is noteworthy that the
    percentage of germination of maize at the beginning of the trials was
    99%, 50 weeks after treatment it was still 97% in grain treated with 5
    and 10 mg bromophos/kg, but only 41% in untreated maize (control).

         In another study reported by Eichler and Knoll (1975), 100 kg
    lots of 15% and 13.5% moisture and as commonly used for being were
    treated experimentally with bromophos at 8 and at 12 mg/kg. The
    insecticide was applied as a dust (12%) and as an emulsion concentrate
    (40%) at each dosage level. These lots were then stored in open
    containers in a room at ambient temperature ranging from 9 to 22C.
    Untreated lots were also stored under similar conditions for
    comparative purposes. Samples of grain were taken from each lot after
    3, 6 and 12 months storage.


        TABLE 2.  Residues of bromophos (mg/kg) in stored maize and sorghum (Selection of data from original report)

                                                                                                              

                                            Storage after application (months)
                                                                                                  

                             0          1             3              6               10          12
                                                                                                              

                   (a)       10         8.7           8.2            6.6             2.3         -

                   (a)       5          -             4.2            1.6             0.7         -

                   (b)       5          3.5-4.3       2.6-3.9        1.4-1.6         -           -

                   (c)       7.5-8      5.1-6.2       3.3-4.9        3.1-5.5         -           -

                   (d)       8          -             -              -               -           1.4

                   (e)       8          7.8-8.0       5.7-6.1        1.3-2.0         -           -
                                                                                                              


                                                        EXPLANATORY NOTES

                                                                                                                                    

                                        Amount of Grain          Moisture
              Type of Storage               (tons)               Content          Temperature         Sampling Arrangements
                                                                                                                                    

    (a)  Vertical cylindrical                                                                       3 samples of 1 kg from surface
         bins holding 725 metre               54.4                12%            12-30 in bins     layer, 20 feet below and at
         tons                                 Maize                                                 bottom. All mixed

    (b)  2 bins, as (a)                       54.4                12%            as (a)             3 samples of 1 kg from the
                                              Maize                                                 upper surface. Mixed

    TABLE 2. (continued)

                                                        EXPLANATORY NOTES

                                                                                                                                    

                                        Amount of Grain          Moisture
              Type of Storage               (tons)               Content          Temperature         Sampling Arrangements
                                                                                                                                    

    (c)  Horizontal bulk containers      Completely filled        12-12.6%       10-32 in bin      4 samples of 1 kg at 4 points at
         holding 1750 metric tons        with maize                                                 surface. Mixed

    (d)  Bags in room 11 m3              Several bags, maize                     28 in room

    (e)  2 bins 725 metric tons               54.4                               12-30 in bins     as (a)
         each                                 Sorghum
                                                                                                                                    
    

         Samples were milled under simulated commercial conditions into
    flour and subsequently made into bread. Others were crushed into a
    wholemeal flour before baking. Analyses were undertaken on various
    samples during the course of the test. These included analyses of raw
    grain, flour, bran and bread. A GLC method, sensitive to about 0.01
    mg/kg was used. Small amounts of 2,5-dichloro-4-bromophenol were found
    in the wheat grains (see Table 3) but not more than traces of
    bromoxone.

    Losses on storage of raw grain

         As indicated in Tables 4 and 5, between 37 and 50% of the
    residues of bromophos disappeared over a 12 month period of storage.
    Supplementary experiments indicated that the rate of degradation was
    greater at higher storage temperatures, reaching about 60% at 26C.


    TABLE 3. Residues of 2,5-dichloro-4-bromophenol (ppm) in wheat grainsa,b

                                                                           

                               Application of            Application of
                                  8 ppm a.i.               12 ppm a.i.
                Months                                                
                after
              application      Dust     Emulsion        Dust     Emulsion
                                                                           

                   6           0.35     0.23            0.44     0.49

                   12          0.40     0.39            0.70     0.80
                                                                           

    a Moisture content: 13.5%.

    b Storage temperature: 15C.

    TABLE 4.  Degradation of bromophos (ppm) in wheat grains;a comparison
              of dust and emulsion

                                                                      

                               Application of         Application of
                                  8 ppm a.i.            12 ppm a.i.
             Months                                               
             after
             applicationb      Dust   Emulsion        Dust   Emulsion
                                                                      

                  0            6.8      5.4           10.4     9.4

                  3            4.3      5.6           7.2      9.2

                  6            4.3      3.5           6.7      6.2

                 12            4.1      3.4           6.1      4.7

             Degradation
                after          40%      37%           41%      50%
               1 year
                                                                      

    a Storage temperature at 15C.

    b Application in February.


    TABLE 5.  Degradation of bromophos (ppm) in wheat grainsa with varying
              moisture content and under varying storage temperatures

                                                                      

               Months
               after         m.c. 13.5%     m.c. 13.5%     m. c. 15%
             applicationb    temp. 15      temp. 26      temp. 26
                                                                      

                  0             9.4             9.4           9.4

                  3             9.2             5.7           5.4

                  6             6.2             5.0           4.7

                  12            4.7             3.6           3.7
                                                                      

    a Application of 12 ppm a.i. as emulsion.

    b Application in February.

    Distribution in milled products

         As has been found with various other pesticides applied to stored
    grain in dust or emulsion concentrate formulations, the bran fractions
    were found to contain the highest residue and the white flour the
    least. Similarly, white bread contained significantly lower residues
    than bread from whole crushed wheat. This is illustrated in Tables 6
    and 7, which indicate the levels that may occur in flour and bread
    following treatment of wheat under commercial conditions. Based on the
    above studies the meeting decided to recommend temporary maximum
    residue levels for wheat, flour and bread.


    TABLE 6. Comparison of bromophos residues (ppm) in flour and bread

                                                                 

                              Application           Application
            Months            of dusta              of emulsiona
            after                                             
           application       Flour    Bread        Flour    Bread
                                                                 

                3            2.34     0.18         2.66     0.30

                6            1.02     0.12         0.99     0.10

                12           1.17     0.08         1.10     0.07
                                                                 

    a Application of 12 ppm a.i.


    TABLE 7. Comparison of bromophos residues (ppm) in crushed grain and bread

                                                                       

                           Application                Application
    Months                 of dusta                   of emulsiona
    after                                                            
    application     Crushed grain     Bread     Crushed grain     Bread
                                                                       

    3               7.2               1.59      9.2               2.48

    6               6.7               1.73      6.2               2.05

    12              6.1               2.23      4.7               1.40
                                                                       

    a Application of 12 ppm a.i.

    IDENTITY OF RESIDUES IN PLANTS

         As already reported earlier (FAO/WHO, 1973) application of
    bromophos to tomato plants resulted in residues of the parent compound
    and 2,5-dichlor-4-bromophenol as a main metabolite. Detailed
    information on this subject was published by Eichler (1972). Following
    application of 1.1 mg of bromophos-3H to tomato plants, residues were
    determined in the waxy layer of treated leaves, the leaves with the
    waxy layer removed, and the remainder of the plant. The results are
    listed in Table 8.

         Manitoba wheat which had been treated with 10 mg bromophos/kg
    contained 3-4 mg of the parent compound after five weeks and showed a
    corresponding rise in levels of 2,5-dichloro-4-bromophenol.
    Desmethylbromphos appeared also as a decomposition product, especially
    three weeks after application, and not more than traces of bromoxon.
    Detailed studies (Rehbinder, 1966) have shown that bromoxon is the
    only metabolite of toxicological significance.

    APPRAISAL

         Data on rate of application, safety intervals and so on reported
    in the 1972 Monograph (FAO/WHO, 1973) have been reviewed. The
    pre-harvest interval was judged to be seven days for the majority of
    fruit and vegetables, four days for cucumbers and tomatoes, 14 days
    for forage, 21 days for radishes, 30 days for kohlrabi and 42 days for
    cabbage, carrots and onions.

         On the basis of residues found in Brussels sprouts and by analogy
    with the temporary tolerance for peas (FAO/WHO, 1973) maximum residue
    limits of 0.5 mg/kg are recommended for Brussels sprouts and of 0.1
    mg/kg are for broad beans (without pods).

         New information on residues in stored maize, sorghum and wheat,
    and on residues in processing of wheat, received in response to the
    requirement at the 1972 meeting was reviewed. This enabled
    recommendations to be made for temporary maximum residue limits for
    these grains and for certain wheat products.

         No recommendations could be made for peanuts and for milk
    products because relevant information had not become available.

         The Meeting considered whether the bromophos metabolite
    2,5-dichloro-4-bromophenol should be included in the proposed maximum
    residue limits. This seems not necessary nor advisable because the
    proportion of 2,5-dichloro-4-bromophenol in the residue is very small
    compared with the bromophos. Furthermore, 2,5-dichloro-4-bromophenol
    is also a degradation product of bromophos-ethyl, leptophos
    O-(4 bromo-2,5-dichlo-phenol) O-ethylphenyl, phosphorothioate and
    similar pesticides.


    
    TABLE 8. Metabolites of bromophos-3H in tomato plantsa

                                                                                                                                           

                                                  Treated leaf
                                                                               
                                                                                      Remainder of plant
                                      Waxy layer              Interior leaf           excluding root                 Whole plant
                                                                                                                                           

                                             Amt. of                   Amt. of                   Amt. of       Amt. of       Percent. of
          Bromophos and          Extract     substance     Extract     substance     Extract     substance     substance     bromophos
    Day   metabolites            (%)         (g)          (%)         (g)          (%)         (g)          (g)          dose applied
                                                                                                                                           

          Bromophos              96          66.5          80          370           66          2.2           438.7         40
          Bromoxon               0.1         0.0           0.4         1.8           1           0.03          1.83          0.1
    1     Dichlorobromophenol    5           2.3           10          30.5          8           0.2           33.0          4.6
                                                                                                                                           
          Total                  101.1       -             90.4        -             75          -             -             44.7
                                                                                                                                           

          Bromophos              74          13.7          63          126           46          2.0           141.7         12.9
          Bromoxon               0.4         0.07          0.5         1.0           7           0.3           1.37          0.2
    2     Dichlorobromophenol    15          1.9           26          34.3          13          0.4           36.6          5
                                                                                                                                           
          Total                  90          -             90          -             66          -             -             18.1
                                                                                                                                           

          Bromophos              9           6.9           7           8.6           11          0.7           16.2          1.5
          Bromoxon               0.4         0.3           0.4         0.5           1           0.06          0.86          0.1
    7     Dichlorobromophenol    94          47.7          58          46.6          16          0.7           95.0          13.1
                                                                                                                                           
          Total                  103.4       -             65          -             28          -             -             14.7
                                                                                                                                           

    a In each case following application of 1.1 mg of bromophos-3H to one leaf of a plant.
    

    RECOMMENDATIONS

         The following additional maximum residue limits (see FAO/WHO,
    1973) determined and expressed as bromophos are recommended.


    MAXIMUM RESIDUE LIMITS

                                                               

                                                 Bromphos
    Commodity                                    (mg/kg)
                                                               

    Bran (wheat)                                    20

    Raw grain (wheat, maize, sorghum)               10

    White flour, wholemeal bread                    2

    White bread                                     0.5

    Brussels sprouts                                0.5

    Broad beans (without pods)                      0.1
                                                               


    FURTHER WORK OR INFORMATION

    REQUIRED  (by 30 June 1977) (in addition to the information listed
    in FAO/WHO, 1973a, p. 42 and before additional maximum residue limits
    can be recommended)

         1.   Residue data on fat of meat of domestic animals other than
              sheep, including residues in milk products, poultry, eggs
              and on peanuts for which recommendations have not been made.

    DESIRED (in addition to the information listed in FAO/WHO, 1973a, p.
    42)

         1.   Further information on residues in stored wheat and on rice
              following storage and processing under full-scale commercial
              conditions.

    REFERENCES

    CCPR Codex Alimentarius Commission of the FAO/WHO. (1975) Report of
    the 8th Session of the Codex Committee on Pesticide Residues. (CL
    1975/13, August 1975)

    Dep. Agr. Techn. Serv. Department of Agricultural Technical Services,
    Pretoria, South Africa. (1975) Report on a trial of bromophos on
    stored maize and sorghum ((25-9-1975) 39/4/9)

    Eichler, D. (1972) Bromophos and bromophos-ethyl residues. Residue
    Reviews, Vol. 41, 65-112. F. A. Gunther, Ed. (1972)

    Eichler, D. and Knoll, H. A. (1975) Degradation of bromophos in stored
    wheat. Proceedings of First International Working Conference of Stored
    Products Entomology, Savannah, USA (7-11 Oct. 1974)

    FAO/WHO. (1973) 1972 Evaluations of some pesticide residues in food.
    WHO Pesticide Residue Series, Nu. 2 (Geneva, 1973)

    Rehbinder, D. (1966) C. H. Boehringer Sohn, Ingelheim, unpublished
    information (see Eichler, 1972)

    RIV (1974) Rijksinstituut v.d. Volksgesondheid, No. 61/74 Tox-Rob
    Residuen van bestrijdingsmiddelen in groenten an fruit in diverse
    stadia vanshoudelijke bereiding (April 1974)

    RIV Rijksinstituut v.d. Volksgesondheid, Unpublished report (U 124/67
    Tox W/ad)
    


    See Also:
       Toxicological Abbreviations
       Bromophos (WHO Pesticide Residues Series 2)
       Bromophos (Pesticide residues in food: 1977 evaluations)
       Bromophos (Pesticide residues in food: 1982 evaluations)
       Bromophos (Pesticide residues in food: 1984 evaluations)