This insecticide was previously evaluated in 1968 (FAO/WHO, 1969) at
    which time an acceptable daily intake and temporary tolerances were
    recommended. Five requirements for further work or information were
    set forth. Since the previous evaluation, additional data and
    information have become available.

    At the Sixth Session of the Codex Committee on Pesticide Residues it
    was requested that further consideration be given to this compound by
    the FAO/WHO Joint Meeting on Pesticide Residues in the light of new
    use patterns and new residue data.



    In the following paragraphs, the numbers refer to the corresponding
    requirement laid down by the 1968 Joint Meeting.

    1.   Extension of use on fruit and vegetables

         There is no anticipated extension of use on fruits or vegetables
         beyond those few commodities currently registered (such as
         bananas for importation into the United States of America and
         Canada), and there would be no need for international tolerances
         for this type of application.

    2.   Animal use pattern and resultant residues from countries other
         than the United States of America and the United Kingdom

         Data in the form of registered labels and tables of registered
         uses did not indicate a use pattern in Canada or residues in
         animals significantly different from that in the United States.

         Supervised trials in Lebanon (Kowar, 1968) in which dairy cattle
         were treated with one application each at levels of 0.38 and
         0.75% fenchlorphos had initial milk residues of about 1.8 ppm one
         day after treatment (high rate). By four days after application,
         no residues were detectable in milk.

    3.   Residue levels in raw agricultural products moving in commerce

         No Information was available.

    4.   Residue levels found in total diet studies in countries other
         than the United States

         Out of 462 subsamples analysed in the total diet survey in
         England and Wales (Abbott, 1970) only one had positive residues
         of fenchlorphos (at 0.09 ppm).

    5.   Evaluation of methods of analysis for regulatory purposes

         Since the 1968 Joint Meeting, several new methods of analysis
         have been developed. One in support of the registration of
         fenchlorphos is based on an adaptation of the procedure of
         Claborn (1965) and utilizes electron capture gas chromatography
         (Dow, 1967).

         The method has been validated down to 0.01 ppm for fenchlorphos
         and to 0.1 ppm for the total metabolites in animal tissues.

         A method for determining fenchlorphos and its oxygen analogue in
         tissues of cattle has recently been published (Ivey, 1971), which
         utilizes flame photometric gas chromatography and can detect
         0.002 ppm fenchlorphos and 0.005 ppm of the oxygen analogue.
         Recoveries were 75-95% for fenchlorphos and 80-100% for the
         oxygen analogue. Since fenchlorphos is listed as one of the
         compounds detectable by the multi-residue gas chromatographic
         method of analysis of Abbott et al. (1970), that method is
         recommended for regulatory use.

    For confirmation, a gas chromatographic method with thermionic
    detection appears suitable (Watts, 1969). The paper describes
    retention times and response data on three different GLC columns.


    A large amount of data was available on residues in fat of cattle,
    sheep, and pigs, in poultry, and eggs, and in milk from a wide variety
    of applications. Table 1 summarizes those data and reflects the
    maximum residues found among all of the applications tested.

    The data in Table 1 indicate that for cattle and sheep (and by
    extrapolation, goats) the possibility exists for residues in fat to
    exceed 7 ppm, but it would never exceed 10 ppm at the recommended
    withdrawal interval. The previously recommended tolerances for meat
    (fat basis) of 7.5 ppm should therefore be increased to 10 ppm for
    cattle, sheep and goats. However, the data further indicate that
    residues in fat of pigs would rarely exceed 2 ppm and residues in
    poultry would not exceed 0.01 ppm; therefore, the tolerances should be
    lowered accordingly.

        TABLE 1  Residues of fenchlorphos in fat of cattle, sheep and pigs


    Animal                Ronnel          Days          Maximum           Recommended
    (route of             (mg/kg/day      withdrawal    residue in        withdrawal
    application)           days)         before        fat or milk       prior to
                                          slaughter     (ppm)             slaughter

    Cattle (oral,         18  7          1             43                10
    in capsule)                           8             6.7
                                          15            0.51

    Cattle (oral          15  22         1             31                10
    mineral feed)                         7             8.5
                                          27            <0.05

    Cattle (oral          8.76  14       0             9.5               10
    mineral feed)                         10            0.40
                                          21            0.026
                                          28            0.001
                                          35            <0.001

    Cattle (spray,        1.0%            7             7.5               14
    aqueous)                              14            1.6
                                          21            0.7
                                          35            <0.05

    Sheep (dip,           0.5%            7             51                28
    1 time, aqueous)                      14            30
                                          21            14
                                          28            9

    Pigs (sprays          0.5%            8             0.66              0
    aqueous)              (100 mg/kg)     14            0.21
                                          21            0.20
                                          28            0.13

    Poultry (litter,      0.5%            42            <0.005 (in mixed muscle)
    water spray)                          60            <0.005 (in mixed muscle)

    Dairy cattle          17.6  7        1             0.029 in milk     10
    (oral, 32P                            2             0.041  "
    labelled feed                         3             0.064  "
    additive)                             7             0.092  "
                                          8             0.072  "
                                          9             0.064  "
                                          10            0.043  "

    TABLE 1  (Cont'd.)


    Animal                Ronnel          Days          Maximum           Recommended
    (route of             (mg/kg/day      withdrawal    residue in        withdrawal
    application)           days)         before        fat or milk       prior to
                                          slaughter     (ppm)             slaughter

    Dairy cattle          0.5%            0.3           0.120 in milk     7
    (spray, aqueous)      1 application   1             0.210  "
                                          3             0.144  "
                                          5             0.052  "

                                          10            0.006  "
                                          17            0.001  "
                                          21            <0.001 "

    The data for milk residues indicate that a low probability exists for
    values in excess of 0.04 ppm. However, it was considered desirable to
    change the previous recommendation for the commodity whole milk to
    milk and milk products (fat basis), in order to indicate where the
    residue would be found (fat) and to accommodate milk products. Using
    the accepted factor of 25 (representing 4% butterfat) the calculated
    residue in milk (fat basis) would be 1.25 ppm. This figure should be
    rounded off to 2 ppm to reflect the degree of sampling error expected
    at such low levels and to conform to the current practice of
    recommending values to only one significant figure in these


    The five items of further work or information required by the 1968
    Joint Meeting are considered to have been met. There was no indication
    of a need to include recommendations for tolerances on fruit and
    vegetables. The use pattern appears to be about the same throughout
    the world. Total diet studies in England and Wales have not shown a
    significant incidence of residues of fenchlorphos in food. Existing
    multi-residue methods of analysis are suitable for regulatory purposes
    and are recommended.

    Consideration of new data on residues likely to occur in meat, milk
    and eggs from a wide variety of new application procedures on
    livestock and poultry has shown that a higher tolerance is required
    for fat of meat of cattle, goats and sheep, but that lower tolerances
    would suffice for poultry and fat of meat of pigs.

    The previously recommended tolerance on whole milk of 0.04 ppm was
    changed to 2 ppm in milk and milk products (fat basis), which is
    equivalent to 0.08 ppm in whole milk, on the basis of the new data



    The temporary tolerances in effect until 1972 are replaced by the
    following tolerances, which include the oxygen analogue.


         Fat of meat of cattle, goats and
         sheep                                                  10

         Fat of meat of pigs, milk and milk
         products (fat basis)                                   2

         Eggs (shell free)                                      0.05

         Poultry                                                0.01*

         * at or about the limit of determination




    Abbott, D.C., Crisp, S., Tarrant, K.R. and Tatton, J.O'G. (1970)
    Pesticide residues in the total diet in England and Wales, 1966-1967.
    III. Organophosphorous pesticides residues in the total diet. Pestic.
    Sci., 1: 10-13.

    Claborn, H.V. and Ivey, M.C. (1965) Determination of O,O-dimethyl
    O-2,4,5-trichlorophenyl phosphorothioate in animal tissues and milk.
    J. Agr. Food Chem., 13: 353-354.

    Dow Chemical U.S.A. (1968) Gas chromatographic determination of
    Ronnel, O,O-dimethyl-O-(2,4,5-trichlorophenyl) phosphorothioate,
    and Ronnel phenolic metabolites in animal tissues. AGR. 68.15, 1968.

    FAO/WHO. (1969) 1968 evaluations of some pesticide residues in food.
    FAO/PL:1968/M/9/1; WHO/Food Add./69.35.

    Ivey, C. and Claborn, H.V. (1971) Gas-liquid chromatographic
    determination of ronnel (O,O-dimethyl-O-2,4,5-trichlorophenyl
    phosphorothioate) and the oxygen analogue of Ronnel (dimethyl
    2,4,5-trichlorophenyl phosphate) in tissues of cattle. J. Agr. Food
    Chem., 19(6): 1256-1258.

    Kowar, S., Bostonian, J. and Badawi, S. (1968) Insecticidal residues
    in the milk of dairy cows treated for control of ectoparasites. J.
    Dairy Sci., 51(7): 1023-1025.

    Watts, R. and Storherr, R.W. (1969) Gas chromatography of
    organophosphorus pesticides: Retention times and response data on
    three columns. J. Ass. off. analyt. Chem., 52(3): 513-521.

    See Also:
       Toxicological Abbreviations