Chlorpyrifos was considered by the Joint Meeting in 1972 and an
    ADI was established (FAO/WHO, 1973). Based on information reported at
    that Meeting and at the 1974 Meeting (FAO/WHO, 1975), a number of
    further recommendations for tolerances were specified on both animal
    and vegetable products.

         During the CCPR Meeting 1975 some delegations expressed opinions
    on individual tolerances reflecting different views on good
    agricultural practices, and specific levels established for poultry
    fat and for milk were questioned. As no information has been received
    concerning residues in vegetable products, the Meeting has only
    considered the questions raised on poultry fats and milk products.


    In poultry fat

         A chicken feeding study by Dishburger et al. (1972) which has
    been brought to the attention of the Meeting elucidates the question
    of chlorpyrifos residues in poultry fat further. In this study laying
    hens were fed chlorpyrifos at rates of 0.3, 1.0, 3.0 and 10 mg/kg for
    30 days. Samples of muscle (with fat and skin), liver, kidney and
    peritoneal fat were analysed, as were eggs from hens fed 10 mg/kg over
    a period of 45 days. Chlorpyrifos and 3,5,6-trichloro-2-pyridinol were
    determined (see Table 1) and analysis showed that the level of the
    parent compound in chicken fat is not likely to exceed 0.1 mg/kg under
    practical circumstances following good agricultural practices.
    Residues of chlorpyrifos in eggs were not detectable.

         Another source of chlorpyrifos residues in poultry fat was
    reported earlier (FAO/WHO, 1973), namely the more specific practice of
    controlling chiggers, Neschongastia americana in turkeys through
    soil-treatments in pens. As a result of this application some of the
    compound is take up by the turkeys and maximum residues of 0.157 and
    0.066 mg/kg in skin and fat respectively were found one week after the
    treatment (Claborn et al., 1970) declining to less than 0.001 mg/kg
    after six weeks.

         While the earlier recommendation of 0.2 mg/kg for chlorpyrifos in
    poultry fat could therefore be lowered to 0.1 mg/kg as far as chicken
    fat is concerned, this would not be justified in the case of turkey
    fat and skin.

    TABLE 1.  Average residues of chlorpyrifos and 3,5,6-trichloro-2-pyridinol in tissues and eggs of chickens fed chlorpyrifos


                                                          Average residues found, mg/kg

                             Chlorpyrifos                                                        3,5,6-trichloro-2-pyridinol
    level in
    feed mg/kg      Muscle   Liver    Kidney   Fat        Eggsa            Muscle     Liver      Kidney          Fat      Eggsa

    0               -        -        -        -          -                -          -          -               -        -

    0.3             -        -        -        -          -                -          ND         ND              -        -

    1.0             -        -        -        ND         -                -          ND         ND-0.11         -        -

    3.0             -        -        -        ND-0.02    -                -          ND-0.06    ND-0.24         -        -

    10.0            ND       ND       ND       0.02-0.06  ND               ND         ND-0.25    ND-0.84         ND       ND-<0.05

    10.0b           -        -        -        ND         -                -          ND         ND              -        -

    a Eggs collected from chickens on treated feed 7-45 days - no withdrawal period.

    b 7-day withdrawal from medicated feed.

    In milk and milk products

         Studies of the transfer of chlorpyrifos into milk after feeding
    cows at the 5 mg/Kg level and reports on milk residues resulting from
    single dip applications were evaluated by the JMPR 1972 and no new
    information has become available.

         In response to the question raised by the CCPR, the Meeting
    reconsidered the data already available and recognized that the
    previous recommendation reflects only the reported feeding studies,
    whereas residues arising from direct dip applications (Table 5 of
    FAO/WHO 1973) may not be sufficiently covered by the established
    maximum residue limit of 0.01 mg/kg. Taking into account the
    increasing use and potential interest in such applications, a maximum
    residue of 0.1 mg/kg is required. In proposing this limit the Meeting
    recognized that the milk from treated cows will, in normal practice,
    be blended with milk from untreated cows and that it would be unlikely
    for more than a proportion of commercial milk to come from recently
    treated cows, even in areas where treatments have to be repeated
    frequently (FAO/WHO, 1972).


         In response to questions raised by the Codex Committee on
    Pesticide Residues, the Meeting has reconsidered the earlier
    established tolerances for chlorpyrifos in poultry fat and milk. Based
    on new information from chicken feeding studies, the earlier
    recommended tolerance of 0.2 mg/kg in poultry fat could be lowered to
    0.1 mg/kg as far as chicken fat is concerned. However, the earlier
    recommendation should be maintained to account for the higher residues
    in fat and skin of turkeys which may arise from soil treatments in
    turkeys' pens in the control of chiggers.

         Having re-evaluated the earlier recommendation for a tolerance of
    0.01 mg/kg for chlorpyrifos in milk (fat basis), the Meeting agreed
    that this level was not adequate to cover residues which may result
    from dip applications to dairy cattle. An increase of the earlier
    proposal to 0.1 mg/kg is appropriate.


         Earlier established tolerances (FAO/WHO, 1973, 1975) should be
    amended as follows, by deleting tolerances for fat of poultry and for
    milk and inserting:


         Commodity                          Maximum residue limit, mg/kg

    Fat and skin of turkey                  0.2

    Fat of chicken                          0.1

    Milk and milk products (fat basis)      0.1

    Eggs (whole)                            0.01*

    * At or about the limit of determination.


    Claborn, H. V., Kunz, S. E. and Mann, H. D. (1970) Residues of Dursban
    in the body tissues of turkeys confined in pens containing treated
    soils. J. Econ. Entomol., 63:422-424.

    Dishburger, H. J., McKellar, R. L. and Wetters, J. H. (1972) Residues
    of chlorpyrifos and 3,5,6-trichloro-2-pyridinol in tissues and eggs
    from chickens fed chlorpyrifos. Report from Dow Chemical USA, Midland,
    Michigan, 31 May.

    See Also:
       Toxicological Abbreviations
       Chlorpyrifos (ICSC)
       Chlorpyrifos (WHO Pesticide Residues Series 2)
       Chlorpyrifos (Pesticide residues in food: 1977 evaluations)
       Chlorpyrifos (Pesticide residues in food: 1981 evaluations)
       Chlorpyrifos (Pesticide residues in food: 1982 evaluations)
       Chlorpyrifos (Pesticide residues in food: 1983 evaluations)
       Chlorpyrifos (JMPR Evaluations 1999 Part II Toxicological)