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    FOLPET       JMPR 1974

         This monograph addendum should be read in conjunction with the
    monograph from the 1973 Meeting (FAO/WHO, 1974, p. 278-280).

    Explanation

         Arising out of the list of requirements published in the report
    of the 1969 Joint Meeting (FAO/WHO, 1970) some information on the
    degradation of folpet, methods of analysis, use patterns in several
    countries and residues resulting from supervised trials therein was
    referred to the FAO Working Party of Experts.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Data on the use pattern in countries other than the U.S.A. was
    required. Information was obtained on the current use patterns of
    folpet in several countries, which is summarized in Table 1.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

         Residue data from supervised trials carried out in countries
    other than U.S.A. was required. New data was obtained from supervised
    trials on apples, peaches, grapes and strawberries (outdoor and
    glasshouse, Table 2).

    FATE OF RESIDUES

         The main degradation mechanisms of folpet are postulated to be
    the same as those for captan (FAO/WHO, 1970). Further information has
    been obtained since then. The IUPAC commission on Terminal Residues
    reviewed these data in its sixth Meeting in 1971. The dicarbonyl
    portion of captan forms imides, phthalamic acids and dicarboxylic
    acids (Lukens, 1966).

         The degradation pattern of the -SCCl3 moiety is more complex. A
    wide range of products containing sulphur in several oxidation states
    have been found (Lukens, 1966). It was shown that volatile products
    are formed such as COS (carbonyl sulfide) and CSCl2 (thiophosgene)
    (Somers, 1967; Lukens and Sisler, 1958b).

         The parent molecule on the CSCl2 moiety reacts with cysteine
    (Lukens and Sisler, 1958a), and/or with various thiols occurring in
    the plant (Richmond and Somers, 1966; Siegel, 1970).

        TABLE 1.  Current use patterns of folpet in several countries

                                                                                      
                                                           Application rate
                                                                    Recommended
                                                                    pre-harvest
    Country       Crops                          g/100l    kg/ha    intervals (days)
                                                                                      

    Canada        Apples                         45-60              1

                  Blueberries, cherries          60        1.25     1

                  Black, red and white
                   currants                      120       1.5      7

                  Gooseberries                   60        1        7

                  Cranberries                              2.25     30

                  Strawberries                   60        1        1

    France        Apples, pears                  100                nil

                  Grapes                         100-175            15

                  Vegetables                     100-125

                  Potatoes                       150                nil

    Netherlands   Apples, pears                                     -

                  Blackberries, raspberries,
                  strawberries (outdoors)        125                4

                  Strawberries (glasshouse)      125                14

                  Red and black currants         125                10

                  Lettuce (glasshouse)                     1.6      21 period March/
                                                                       November

                                                                    42 period November/
                                                                       March

    South Africa  Pome fruits, stone fruits,
                  citrus fruits, potatoes,
                  tomatoes                       60                 nil
                                                                                      



    
    TABLE 2.  Supervised trials with folpet in several crops (Part A: 0-10 days)

                                                                                                                      

                              Application
    Country                       Rate kg                                Pre-harvest interval in days
    Crop                 No       a.i./ha      Formulation      0-1            2-4            5-7            8-10
                                                                                                                      

    Netherlands3
     Apples              1        2.0          w.p. 50%         1.48-1.60      1.41-1.57      1.39-1.47      1.07-1.47

    Netherlands3
     Red currants        5        2.251        w.p. 50%         17-4-33.6      9.0-33.6       8.1-13.2       5.1-16.3

    Netherlands3
     Raspberries         5        125g/100 l   w.p. 50%         10.5-24.3      7.3-25.3       6.2-12.6       7.7-9.6

                         2        125g/100 l   w.p. 50%         12.7-19.6      5.8-10.9       2.5-7.0        0.2-

    Netherlands3
     Strawberries        5        125g/100 l   w.p. 50%         0.6-1.1        0.8-1.7
    (outdoor)            2        125g/100 l   w.p. 50%         0.3-0.5        0.1-0.4

    Netherlands3
     Strawberries        1        2            w.p. 75%                                                      1.8-3.1
     (glasshouse)        2        2            w.p. 75%                                                      1.8-2.8
                                                                                                                      

    1 1.5 x normal rate

    2 After 49 days

    3 Food Inspection service of the Netherlands (1965 and 1967).

    4 Chevron Chemical Company (undated)

    TABLE 2.  Supervised trials with folpet in several crops (Part B: 11-35 days)
                                                                                                                      

                              Application
    Country                       Rate kg                                Pre-harvest interval in days
    Crop                 No       a.i./ha      Formulation      11-14          16-21          22-28          29-35
                                                                                                                      

    Netherlands3
     Red currants        5        2.251        w.p. 50%         1.8-8.1        n.d.-1.5

    France4
     Grapes              4        1.5          w.p. 50%                                                      n.d.
     (crushed)           4        1.5          w.p. 50%                                       n.d.
                         4        1.65-1.75    w.p. 50%                                                      2.1
                         8        0.9-2.1      w.p. 50%                                                      0.31
                         4        1.2          w.p. 50%.                                      0.83
                         4        0.8-1.2      w.p. 50%                                       n.d.

    Netherlands3
     Lettuce             3        1.6          dust 8%                         8.5-14.1       0.3-1.4
     (glasshouse)        3        1.6          dust 8%                                        10-0-17.3      4.3-6.5

    France4
     Peaches             2        1.85         w.p. 50%                        n.d.-0.28

    Netherlands3
     Strawberries        5        125g/100 l   w.p. 50%         0.1-0.3
     (outdoor)           2        125g/100 l   w.p. 50%         0.1-0.2

    Netherlands3
     Strawberries        1        2            w.p. 75%                        1.2-1.3        1.8-2.2
     (glasshouse)        2        2            w.p. 75%                        1.6-2.4        2.0-3.0
                         3        2.1          w.p. 83%                        7.8-12.6                      0.5-5.62
                         3        2.1          w.p. 83%                        4.2-10.6       1.6-5.0
                                                                                                                      

    1 1.5 x normal rate
    2 After 49 days
    3 Food inspection service of the Netherlands (1965 and 1967).
    4 Chevron Chemical Company (undated).
    

    METHODS OF RESIDUE ANALYSIS

         Kilgore et al. (1967) developed a gas liquid chromatography
    method of analysis for folpet and captan. Since then the GLC method
    has been modified and improved (Pomerantz and Ross, 1968; Archer and
    Corbin, 1969). The limit of detection is about 0.01 mg/kg.

         The above mentioned methods are suitable or can be adapted for
    regulatory purposes.

         TLC methods are also available, but these are less sensitive
    (Engst and Schnaak, 1967).

    NATIONAL TOLERANCES

         Examples of national tolerances of folpet residues are reported
    in Table 3.

    TABLE 3.  Examples of national tolerances reported to the Meeting

                                                                             

                                                                   Tolerance
    Country        Commodities                                       mg/kg
                                                                             

    Canada         Celery                                          30

                   Apples, avocados, blackberries,
                   blueberries, boysenberries,
                   cherries, crab apple, cranberries,
                   black, red and white currants,
                   dewberries, gooseberries,
                   grapes, huckleberries, leeks,
                   lettuce, loganberries, onions,
                   raspberries, strawberries, tomatoes             25

                   Citrus fruit, cucumbers, garlic,
                   melons, pumpkins, squash                        15

    Belgium        Fruit and vegetables                            15

    France         Fruit and vegetables                            15

    Democratic     Pome fruits (apples and pears),
    Republic of    bananas, citrus fruit, black, red
    Germany        and white currants, gooseberries,
                   stone fruits, strawberries                      5

                   Brassicas, fruits of vegetables,
                   green beans, leafy vegetables, peas,
                   potatoes                                        0.1

    TABLE 3.  (Cont'd.)

                                                                             

                                                                   Tolerance
    Country        Commodities                                       mg/kg
                                                                             

                   Cereals, onions, meat, fat of meat,
                   fish, milk, eggs, vegetable oils
                   and fats                                        0

    Federal Rep.   Fruit and vegetables                            15
    of Germany
                   Other agricultural crops                        0.1

    Hungary        Fruit, including grapes, vegetables             15

    Switzerland    Fruit, including grapes                         15

    United States  Celery, Cherries, leeks, lettuce,
                   onions (green), shallots                        50
                   Apples, avocados, blackberries,
                   blueberries, boysenberries,
                   crab apple, cranberries, red and
                   white currants, dewberries,
                   gooseberries, grapes, huckleberries,
                   loganberries, raspberries,
                   strawberries, tomatoes                          25

                   Citrus fruit, cucumbers, garlic,
                   melons, onions (dry bulb), pumpkins,
                   summer squash, winter squash                    15

    Yugoslavia     Fruit, vegetables, other agricultural
                   crops                                           15
                                                                             


    APPRAISAL

         In the light of present information about the nature and fate of
    terminal residues and the knowledge that the available analytical
    procedures are adequate for regulatory purposes the meeting agreed
    that the requirement for collaborative studies on analytical methods
    was no longer necessary.

         The Meeting was advised that results of further metabolism
    studies should be available in 1975.

    RECOMMENDATIONS

    TOLERANCES

         The tolerances recommended in 1969 have been confirmed as no
    longer necessary.

         The tolerance previously proposed for strawberries has been
    amended and additional tolerances are recommended. These are based on
    residues likely to be found at harvest following currently approved
    use patterns.
                                       Interval on which
                                       recommendations 
    Crop                  ppm          are based (days)
    

    Strawberries          20                 14
    Lettuce               15                 14

    FURTHER WORK OR INFORMATION

    DESIRABLE

    1.   Information on the nature, level and fate of residues following
         washing, blanching, storage and thermal processing of treated
         crops.

    2.   Residue data obtained by newer methods of analysis on the main
         commodities for which tolerances have been recommended.

    3.   Information on the fate of residues in soil.

    4.   Further data on the quantities of degradation products in
         relation to residues of the parent compound.

    5.   Results of metabolism studies currently planned.

    REFERENCES

    Archer, T.E., and Corbin, J.B. (1969) The site and fate of captan
    residues from dipping prunes prior to commercial dehydration. Food
    Technol. 23:235-238.

    Chevron Chemical Company. Data provided to Joint Meeting.

    Engst, R. and Schnaak, W. (1967) Dünnschichtchromatographische
    Bestimmung von Rückständen der Fungizide Captan und Phaltan. Nahrung,
    11:95-100.

    FAO/WHO. (1970) 1969 Evaluations of some pesticide residues in food.
    FAO/PL/1969/M/17/1; WHO/Food Add./70/38.

    FAO/WHO. (1974) 1973 Evaluations of some pesticide residues in food.
    FAO/AGP/1973/M/9/1; WHO Pesticide Residues Series, No. 3.

    Food Inspection Service of the Netherlands, Amsterdam, (1965, 1967)
    Reports 47, 68, 76, 88, 101, 106 and 122. (Unpublished).

    IUPAC. (1971) Minutes of the sixth Meeting of the IUPAC Commission on
    Terminal Residues, Washington, D.C., July 1971.

    Kilgore, W.W., Winterlin, W. and White, R. (1967) Gas chromatographic
    determination of captan residues. J. agr. Food Chem., 15(6):1035-1037.

    Lukens, R.J. (1966) The fungitoxicity of compounds containing a
    trichloromethyl-thio-group. J. agr. Food Chem., 14(4):365-367.

    Lukens, R.J. and Sisler, H.D. (1958a)
    2-Thiazolidinethione-4-carboxylic acid from the reaction of captan
    with cysteine. Science, 127:650.

    Lukens, R.J. and Sisler, H.D. (1958b) Chemical reactions involved in
    the fungitoxicity of captan. Phytopathology, 48:235-244.

    Pomerantz, I.H., Miller, L.J. and Kava, G. (1970) Extraction, cleanup,
    and gas-liquid chromatographic method for the analysis of captan,
    folpet and Difolatan in crops. J. Ass. off. Analyt. Chem.,
    53(1):154-157.

    Pomerantz, I.H., and Rose, R. (1968) Captan and structurally related
    compounds: thin layer and gas-liquid chromatography. J. Ass. off.
    analyt. Chem., 51(5):1058-1062.

    Richmond, D.V., and Somers, E. (1966) Studies on the fungitoxicity of
    captan. IV. Reactions of captan with cell thiols. Ann. Appl. Biol.,
    57:231-240.

    Siegel, M.R. (1970) Reactions of certain trichloromethyl sulfenyl
    fungicides with low molecular weight thiols. J. agr. Food Chem.,
    18(5):819-822, 823-826.

    Siegel, M.R., and Sisler, H.D. (1968) Fate of the phthalimide and
    trichloromethylthio (SCCl3) moieties of folpet in toxic action on
    cells of Saccharomyces pastorianus. Phytopathology, 58:1123-1128.

    Siegel, M.R. and Sisler, H.D. (1968) Reactions of folpet with purified
    enzymes, nucleic acids, and subcellular components of Saccharomyces
    pastorianus. Phytopathology, 58:1129-1133.

    Somers, E., Richmond, D.V. and Pickard, J.A. (1967) Carbonyl sulphide
    from the decomposition of captan. Nature, 215:214.
    


    See Also:
       Toxicological Abbreviations
       Folpet (HSG 72, 1992)
       Folpet (ICSC)
       Folpet (FAO/PL:1969/M/17/1)
       Folpet (WHO Pesticide Residues Series 3)
       Folpet (Pesticide residues in food: 1984 evaluations)
       Folpet (Pesticide residues in food: 1986 evaluations Part II Toxicology)
       Folpet (Pesticide residues in food: 1990 evaluations Toxicology)
       Folpet (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)