Sponsored jointly by FAO and WHO


    The monographs

    Data and recommendations of the joint meeting
    of the FAO Panel of Experts on Pesticide Residues
    in Food and the Environment and the
    WHO Expert Group on Pesticide Residues
    Rome, 24 September - 3 October 1984

    Food and Agriculture Organization of the United Nations
    Rome 1985



         Cypermethrin was reviewed by the MJPR in 1979, 1981 and 1982 and
    MRLs have been recommended on a wide range of crops and on meat and
    milk. 1/ Data on residues in tea have now been evaluated.



         Cypermethrin is used for the control of insect pests of tea in
    Malawi, Indonesia and experimentally in southern India. The main pests
    of tea that are susceptible to cypermethrin are thrips, Helopeltis
    antonii, H. febriculosa, H. schoutedeni and H. theivora,
    as well as the lepidopterous pests, the tea tortrix (Homona
    coffearia) , slug caterpillar (Thosea sinesis), Darma trima,
    nettle grub (Setora nitrens), tea leaf roller (Gracillaria
    theivora), and Laspeyresia leucostoma.

         Application rates and timing of applications are influenced to
    some extent by the pest. Thus, thrips and Helopeltis require rates
    of from 25 g a.i./ha, whereas up to 40 g may be needed for some of the
    lepidopterous pests.

         More than one treatment may be needed each season, but never more
    than one treatment between pickings; the preharvest interval is
    typically a minimum of five days.



         Most of the data available were obtained from Malawi in a series
    of trials carried out in late 1981 (Bosio, 1982a). Studies were
    carried out at four locations, three with China tea and one with
    Indian. Plot sizes were 100 sq.m. and treatments were applied at the
    rates of 10, 20 or 40 g a.i./ha. The number of treatments was 1, 2, 3
    or 7 with generally about a month between each application, except in
    the case of the three-application experiment where the interval
    between applications was about two weeks. The tea was harvested at
    various intervals after treatment. The leaves were then dried and
    processed and sent to the laboratory. The intervals between the last
    application and harvest ranged from 1 to 29 days, although in practice
    the minimum preharvest interval (PHI) in Malawi is about five days.

         The dry tea samples were analysed for residues of cypermethrin
    and the results are given in Table 1.


    1/  See Annex 2 for FAO and WHO documentation.

        TABLE 1.  Residues of Cypermethrin in Tea from Supervised Trials, Malawi


    Trial             Application                          Residues (mg/kg in dry leaves)
                                                          after preharvest interval (days)
    No.            No.      Rate                                                                                  
                         (g a.i./ha)   1         3         5         7         10        14        20        29

    5              1         10        9.2                 3.5                 2.3                 0.2
                             20       16                   7.3                 4.3                 0.2
                             40       24                  12*                  9.7                 0.7*
    6              2         10        5.7                 1.8                 0.5                 0.1
                             20       10                   4.0                 0.7                 0.1
                             40       11                   8.1                 1.0                 0.1
    7              3         20                  4.3                 1.7       0.4       0.2                 0.03
    8              7         20                  4.6                 2.1       0.3       0.1                 0.01

    *  Samples used for further investigations concerning metabolites.
    1  See Annex 2 for FAO and WHO documentation.

         The results show that with a PHI of five days, cypermethrin
    residues were below 20 mg/kg in every case. The concentrations were
    not noticeably affected by the number of applications, but the rate of
    application and the PHI were both important factors, particularly the

         Two samples of dry tea were also obtained from Indonesia (Bosio,
    1980). The tea was treated three times at weekly intervals with 10 g
    a.i./ha and sampled six days after the last application. The samples,
    which arrived in the laboratory 12 days after harvest, were analysed
    as for the Malawi samples. The residues reported were low, being 0.10
    and 0.15 mg/kg dry tea.

         As described in the 1979 Evaluations (FAO/WHO 1980b),
    cypermethrin degrades in biological systems, primarily by hydrolysis
    of the ester linkage, to give the cyclopropane carboxylic acid (CPCA;
    WL 4476) and 3-phenoxybenzoic acid (3-PBA; WL 44607). The amide
    analogue of cypermethrin (WL 47133) formed by hydrolysis of the cyano
    group without breakage of the ester link has also been reported as a
    metabolite, but only a minor one.

         In other crop commodities, none of these metabolites has been
    detected but they have occurred in tea. Thus, two samples of dry tea
    from one of the Malawi trials, those marked with an asterisk in Table
    1, were analysed for the presence of metabolites (Bosio, 1982b). The
    results are given in Table 2. In both samples, the CPCA moiety was
    found. In the sample with higher residue concentrations there was a
    small amount of 3-PBA, although neither sample contained detectable
    levels of the amide compound.

    TABLE 2.  Residues of cypermethrin metabolites in dry tea 
              leaves (mg/kg)


    Parent         3 PBA          CPCA           Amide

    12             0.13           1.1            <0.03

    0.7            <0.05          0.45           <0.03

         Residues of pesticides in tea are significant to the consumer
    only insofar as they occur in the tea when it is drunk. To estimate
    the concentration of cypermethrin likely to occur in tea infusions,
    all the tea samples from the Malawi experiments were used to brew tea
    and the infusions analysed for cypermethrin content. The dry tea (6 g)
    was infused with 360 ml boiling water, allowed to stand for five
    minutes and then strained off. The infusions were analysed as for the
    dry tea with the very low limit of determination of 0.01 ug/l. Data
    for those samples giving residues above the 0.01 ug/l in the brewed
    tea are summarized in Table 3. Only very low concentrations occurred

    in the infusions, the highest being about 0.25 ug/l from two samples
    of dry tea with 11 and 8 mg/kg cypermethrin residue. Cypermethrin was
    not detected (limit of determination 0.01 ug/l) in any infusions made
    from dry tea with a residue of less than 1 mg/kg cypermethrin.

         The percentage extracted into the infusion was extremely small,
    as would be expected from the lipophilic nature of cypermethrin. In no
    case did the percentage of cypermethrin extracted into the infusion
    exceed 0.2 percent. The average value based on the results in Table 3
    was 0.1 percent.

         The two samples from Indonesia were also used to make infusions,
    but as would be expected from the very low concentrations of
    cypermethrin in them, no residues were found in the infusions.
    (In this earlier work, the limit of determination was much higher at
    0.2 ug/l.)

         Infusions were also made from the two dry tea samples from Malawi
    that were analysed for metabolites, using methodology comparable to
    that employed for the dry tea. The results are shown in Table 4.

         Thus, the process of brewing tea is relatively effective for the
    extraction of residues of the CPCA metabolite, as distinct from
    residues of the parent compound. Although a low concentration of 3-PBA
    was detected in the higher residue sample of dry tea, none was
    detected in the corresponding infusion. No amide compound was detected
    in the infusion.


         In response to requests made at the sixteenth Session of the CCPR
    by several countries, the meeting reviewed earlier residues data on
    lettuce, grapes, peaches, nectarines and pome fruit (1979, 1981 and
    1982 evaluations).

         The meeting accepted that harvest intervals for grapes were
    likely to be 14 days or longer and agreed that the estimate of the
    maximum residues level could be revised to 0.5 mg/kg. The only residue
    exceeding 0.5 mg/kg at 14 days was from a trial in Canada, a country
    for which there is no submitted good agricultural practice. This
    change enabled the meeting to propose a group MRL of 0.5 mg/kg for
    small fruits and berries to replace separate limits for gooseberries,
    raspberries, strawberries, grapes and currants (black, red and white).

         The data on peaches (nectarines were added by extrapolation from
    the data on peaches) indicate that, at the highest doses included in
    GAP and with intervals of 14 days, the levels can exceed 1 mg/kg. The
    meeting, therefore, confirmed its earlier estimate of 2 mg/kg for
    peaches and nectarines. Similarly, the meeting confirmed its estimate
    of 2 mg/kg as the maximum residue level for pome fruit and lettuce if
    an interval of 7 days is used as a basis for GAP.

        TABLE 3.  Residues of cypermethrin in tea infusions made from 
              dry leaves with known cypermethrin content


    Trial          In dry         In tea           Percentage
    No.            tea            infusion         extracted 1
                                  (mg/kg)          (g/l)

    15              9.2           0.02             0.01
                   16             0.04             0.01
                   24             0.10             0.02
                   12             0.08             0.03
                    9.7           0.04             0.02

    6               5.7           0.14             0.1
                    1.8           0.09             0.2
                   10             0.15             0.1
                    4             0.06             0.1
                   11             0.24             0.1
                    8.1           0.24             0.2

    7               4.3           0.07             0.1
                    1.7           0.04             0.1

    8               2.1           0.03             0.1

    1  On basis of 1 g/l equivalent to 0.05 mg/kg dry tea; average
       percentage extracted = 0.1.

    TABLE 4.  Residues of cypermethrin metabolites in tea infusions


    Residues in infusion (g/l)                 Calculated equivalent
                                                 in dry tea (mg/kg)

    Parent    3PBA      CPCA     Amide          Parent      CPCA

    0.08      <0.01     11       <0.05          0.005       0.7

    <0.01     <0.01     2.8      <0.05          -           0.2
         New data on cypermethrin residues in tea enabled the meeting to
    estimate a maximum residue level of 20 mg/kg in dry leaves (the
    commodity in trade). Only 0.1 percent of the residue is extracted into
    the tea infusion.

         After reviewing some of the previous proposals for cypermethrin
    the meeting agreed to propose several changes.

         The definition of kidney beans (in pod) should be replaced by
    beans (with pod) at the same level. The meeting also proposed that an
    estimate of 0.05 mg/kg for legume oilseeds should replace separate
    estimates of 0.02 mg/kg for peanuts and 0.05 mg/kg for soybeans. The
    level of 0.05 mg/kg was identified as at or about the limit of
    determination for all commodities except milk.

         The meeting noted that:

         (1)  the MRL of 0.5 mg/kg for peppers, proposed by the 1981 JMPR,
              was recorded in the evaluations of that year as applying
              separately to sweet peppers and chilli peppers, and

         (2)  that the 1981 report referred to "coffee beans" and the
              evaluations to "coffee (dried beans)".

    The meeting agreed that the correct commodity descriptions are
    "peppers" and "coffee beans".

         The proposal of 0.2 mg/kg for milk products was withdrawn to
    accord with decisions made at the 15th Session of the CCPR on these
    processed foods.


         The following MRLs were estimated and recommended as suitable for


         Commodity      MRL            Preharvest interval on
                        (mg/kg)        which MRL is based (days)

         Small fruits
         and berries    0.05           14 (replacing separate limits
                                       for grapes, currants,
                                       gooseberries, raspberries and

         Tea            20             -

    Further changes in MRLs or commodity descriptions were recommended:

         -    Replace kidney beans (in pod) by beans (with pod) at the
              same level;

         -    Replace peanuts, 0.02 mg/kg, and soybeans, 0.05 mg/kg, by
              legume oilseeds, 0.05 mg/kg;

         -    Withdraw proposed MRL for milk products of 0.2 mg/kg.

    All MRLs at 0.05 mg/kg should be indicated as at or about the limit of
    determination. (The MRL for milk, 0.01 mg/kg, should not be so


    Bosio, P.G. Report BEGR. 80.038 submitted by Shell Chimie to FAO.
    1980      (Unpublished)

    Bosio, P.G. Report BEGR. 82.097 submitted by Shell Chimie to FAO.
    1982      (Unpublished)

    Bosio, P.G. Report BEGR. 82.106 submitted by Shell Chimie to FAO.
    1982b     (Unpublished)

    See Also:
       Toxicological Abbreviations
       Cypermethrin (EHC 82, 1989)
       Cypermethrin (HSG 22, 1989)
       Cypermethrin (ICSC)
       CYPERMETHRIN (JECFA Evaluation)
       Cypermethrin (PIM 163)
       Cypermethrin (Pesticide residues in food: 1981 evaluations)
       Cypermethrin (Pesticide residues in food: 1982 evaluations)
       Cypermethrin (Pesticide residues in food: 1983 evaluations)