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    PESTICIDE RESIDUES IN FOOD - 1980


    Sponsored jointly by FAO and WHO






    EVALUATIONS 1980





    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, 6-15 October 1980




    PERMETHRIN

    Explanation

    Permethrin was reviewed at the 1979 Meeting, when a temporary
    acceptable daily intake (ADI) of 0.03 mg/kg bodyweight was
    recommended.  Maximum residue limits (MRL's) were set for residues of
    permethrin itself on a wide range of agricultural and horticultural
    crops (FAO/WHO, 1980).

    Further data on certain aspects of permethrin usage were requested for
    future reviews and as a result additional data are now reviewed.

    Special note - In this review the term permethrin refers to material
    which is nominally 40:60 () cis:trans permethrin.


    RESIDUES IN FOOD

    USE PATTERN

    Pre-harvest

    Permethrin is a pyrethroid insecticide with a high level of activity
    against Lepidopterous pests.  It is also effective against a wide
    range of Hemiptera, Diptera and Coleoptera.  The compound is both a
    stomach and a contact insecticide, and shows adulticidal, ovicidal
    and, particularly, larvicidal activity.  It is also extremely
    effective against the great majority of insects resistant to commonly
    used insecticides, such as organochlorines and organophosphates.

    Unlike natural pyrethrins and earlier synthetic pyrethroids,
    permethrin is relatively stable to degradation in sunlight.  This
    allows it to be used as a practical tool in agriculture.  Permethrin
    is not plant-systemic and has very little fumigant or translaminar
    activity, a programme of sprays is usually required.

    Pre-harvest use patterns, including those on forage crops, were
    reviewed at the 1979 Meeting (FAO/WHO, 1980).  The effective use rates
    on various forage crops are shown in Table 1.  In reviewing
    pre-harvest uses, the 1979 Meeting noted that in several countries
    target pests and use patterns are well defined, and pre-harvest
    withholding intervals reflecting good agricultural practice in those
    outlets are capable of being specified.  However in many other
    countries, particularly of the third world, and where climatic
    conditions are conducive to a rapid build-up of insect infestations,
    it is important to make available the full flexibility of a compound
    such as permethrin.  Therefore in very many countries no pre-harvest
    withholding intervals are specified.  This in made possible by a
    combination of the low effective use rates and resulting comparatively
    low residues immediately after spraying.  It should also be noted that
    permethrin residues on sprayed crop parts decline relatively slowly.

    Therefore any benefit of a pre-harvest withholding interval as a means
    of reducing residue levels tends to be less than that which accrues,
    for example, with those organophosphate or carbamate insecticides that
    show comparatively short persistence on sprayed plants.



        TABLE 1.  Effective Use Rates for Permethrin On Field Crops

                                                                                                                                 
    Crop            Countries        Examples of Pests Which May Be Controlled                          Rates      Pre-Harvest
                                                                                                      (g ai/ha)    Withholding
                                                                                                                    Interval
                                                                                                                                 
    Cotton            USA            Heliothis virescens, H. zea, Anthonomus grandis,                  110-220       14 days
                                     Pectinophora goosypii, Lygus spp., Trichoplusia ni,
                                     Bucculatrix thurberiella, Trialeurodes abutilonea,
                                     Aphis gossypii.
                     Africa          Earias, Diparopsis, Heliothis, Pectinophora,                       75-200    Non-specified
                                     Empoasca.
                 Rest of World,      Heliothis, Earias, Spodoptera, Pectinophora,                       75-200     up to 7 days
                 including Central/  Cryptophlebia, Diparopsis, Bucculatrix,
                 South America and   Estigmena, Anthonomus, Lygus, Horcias,
                 Caribbean           Trichoplusia, Sacadodes, Eutinobothrus,
                                     Bemisia, Alabama, Dysdercus, Helopeltis, 
                                     Frankliniella, Caliothrips.

    Soya             Brazil          Anticarsia gemmatalis, Trichoplusia ni                             30-100       60 days
                      USA            Pseudoplusia includens, Trichoplusia ni,                           55-100       21 days
                                     Anticarsia gemmatalis, Nezara viridula,
                                     Plattypena scabra, Epilachna varivestis

                                     Heliothis armigera, Laphygma exigua.                              110-220       60 days

    Alfalfa           USA            Hypera spp., Lygus spp.                                            55-220     up to 3 days

    Maize           Australia        Heliothis, Spodoptera, Pyrausta, Sesamia,                          up to        Typically
                     Canada          Peridroma, Pseudaletia, Busseola, Agrotis,                          330           1 day
                     Germany         Oscinella
                   South Africa
                      USA

    Oil seed Rape  Western Europe    Meligothes spp., Apion spp., Ceutherrhynchus spp.                  50-100      (Generally 7 
                                                                                                                    weeks or more)

    Sorghum          Brazil          Spodoptera frugiperda                                                50          45 days
                                                                                                                                 
    

        TABLE 2. Effective Use Rates For Permethrin In Animal Health (Spray Applications)

                                                                                                 
                                                   Maximum         No. of       Interval between
    Target         Country      Pest                 Rate       applications      applications
                              controlled         (g ai/head)     per season          (days)
                                                                                                 
    Cattle           USA      Biting and       )              (             )
                              nuisance flies,  )              (       5     )          14
                              ticks;           )      1.5     (             )
                              lice & mites     )              (       2     )

    Sheep                     Biting and       )              (
                              nuisance flies,  )              (       4                21
                              ticks;           )      2.0     (
                              keds             )              (       2                14

    Pigs                      Biting and       )              (              )
                              nuisance flies,  )              (       5      )
                              ticks;           )      0.5     (              )         14
                              lice & mites     )              (       2      )

    Poultry                   Biting and       )              (
                              nuisance flies,  )              (       3                28
                              ticks;           )     0.025    (
                              lice & mites     )              (       2                14

    Buildings,                Biting and          0.01 g ai/m2    as necessary    as necessary
    Breeding sites            nuisance flies
                                                                                                 
    

        TABLE 3. Effective Use Rates For Permethrin in Animal Health (Spray Applications)

                                                                                                       
                                                      Maximum            No. of       Interval between
    Target            Country           Pest            Rate          applications      applications
                                     Controlled      (g ai/m2)         per season
                                                                                                       
    Dairies           Canada         House flies        0.05          as necessary       as necessary
    Feedlots                         Stable flies
    Stables
    Livestock barns
                                                                                                       
    


    TABLE 4.  Effective Use Rates For Permethrin In Animal Health (Dust
    Applications)

                                                                 
    Target      Country      Pest              Maximum Rate
                             Controlled        (g ai/head)

    Cattle        USA        Biting and           0.175-0.7
    Horses                   nuisance flies,
                             ticks and lice

    Pigs                     Biting and           0.075-0.3
                             nuisance flies,
                             ticks and lice
                                                                 

    Post-harvest

    Apart from its pre-harvest usage, permethrin has an important
    application in the protection of stored grain, being particularly
    useful when used in conjunction with organophosphorus (O/P)
    insecticides (for example) to control insect species that are
    O/P-resistant.

    Permethrin has been applied at 1 mg/kg grain in large-scale trials in
    Australia.  At this level a single application of permethrin,
    synergised with piperonyl butoxide, adequately controls the common
    strains of Rhyzopertha dominica (the less grain borer), the most
    destructive stored grain insect in Australia.  When used in conjuction
    with 4-6 mg pirimiphos-methyl/kg grain, the common strains of storage
    grain insects are controlled for at least 9 months.  Pirimiphos-methyl
    does not control R. dominica.  On the other hand, at the 1 mg/kg
    grain rate, permethrin does not control Tribolium species (e.g. T.
    castancum, the rust red flour beetle, which is presently the most
    prevalent insect pest in Australian stored grain).  Laboratory studies
    have shown that when used at 4-5 mg/kg grain, a single application of
    permethrin does give adequate control of all the commonly occurring
    strains of storage insect pests when the grain is dry and cool.  This
    indicates a future option of varying pyrethroid and organophosphorus
    protectant rates, in a complementary manner, to overcome future
    problems due to insect resistance, absence of a synergist and/or lack
    of a complementary insecticide.  The future application rates of
    permethrin could be raised above the present 1 mg/kg grain level,
    though probably not above 2 mg permethrin/kg grain.


    Ectoparasite uses

    Permethrin can be used as a dust, spray or dip to control biting and
    nuisance flies, ticks, lice, mites and keds, on cattle, goats, horses,
    sheep, pigs and poultry (for effective use rates see Tables 2-4).  It
    can also be used to kill flies in or around agricultural buildings and
    on insect breeding or resting sites for the control of house flies

    (Musca domestica) and stable flies (Stomoxys calcitrans), for
    which it is sold under the trade name `Ectiban' (ICI).


    RESIDUES RESULTING FROM SUPERVISED TRIALS

    Pre-harvest uses (forage crops)

    A large body of residues data from supervised trials was reviewed at
    the 1979 Meeting (FAO/WHO, 1980), which noted that permethrin and its
    metabolites are effectively non-systemic in plants.  Residues are
    highest when crop parts which are consumed are exposed to the spray,
    as in the case of forage crops (Table 5).  Residue levels decline
    comparatively slowly - the 1979 Meeting noted that "half-lives"
    ranging from about one to three weeks depending on the crop, had been
    demonstrated (FAO/WHO, 1980).  The major degradation products are the
    cis and trans isomers of 3-(2,2-dichlorovinyl)-
    2,2-dimethylcyclopropane carboxylic acid (DCVA) plus 3-phenoxybenzyl
    alcohol (3-PBAlc) (Figure 1), which are present primarily as
    conjugates and which are also animal metabolites.  Although residue
    levels of permethrin, DCVA or 3-phenoxybenzyl alcohol on repeated
    applications within the rates and frequency of spraying which are
    needed to obtain good insecticidal control. Ground and aerial
    applications yielded similar permethrin residue levels in a wide range
    of crops (FAO/WHO, 1980).

    FIGURE 1

    FIGURE 2

    In forage crops such as alfalfa, residue levels of the metabolites
    DCVA and 3-phenoxybenzyl alcohol are small compared with the
    corresponding permethrin residues.  This pattern was found on a range
    of crops reviewed at the 1979 Joint Meeting which proposed maximum
    residue limits based upon permethrin itself only (FAO/WHO, 1980).

    In addition to crops grown specifically for forage, livestock feed can
    also contain by-products of food processing (e.g. apple pomace, cotton
    cake).  Residue levels in these commodities are reviewed under "Fate
    on Processing".

    Post-Harvest Uses

    The only significant post-harvest use of permethrin is its application
    to bulk stored grain.  This has undergone extensive laboratory studies
    and silo-scale trials for this purpose in Australia.  Since 1977 some
    10,000 tons of grain have been treated in silo-scale pilot trials in
    five of the Australian States.  All the residue studies show that
    permethrin is persistent on grain under the conditions of temperature
    and moisture content prevailing in Australian storages (Table 6)
    (Desmarchelier et al, 1979).  Initial residues on grain were about
    20% below the level expected from the amount applied.  The residue
    hardly declined in 9 months storage: after 6-9 months about 80% of the
    initial (1 month) residue in grain remains.  This level of persistence
    is found consistently in studies on wheat, barley and sorghum, and
    probably can be generalised for all stored grain (Bengston et al,
    1979a, b, c; Desmarchelier et al, 1979).  Also, studies show that
    the initial ratio of cis/trans isomers is not changed during 8 months
    of storage (Table 7) (Simpson, 1979).




        Table 5, Sheet 3 (Permethrin Residues On Field Crops [Or Crop Parts] Used For Forage)

                                                                                                                                               
    Crop         Country and  Formulations    Rate of       Volume       Number of       Interval       Lowest      Highest    Mean   Reference
                     Year         Used      Application    of Spray    Applications    Between Last     Residue     Residue   Residue
                                             (g ai/ha)      (l/ha)                     Spraying and   Determined  Determined  (mg/kg)
                                                                                          Harvest       (mg/kg)     (mg/kg)
                                                                                                                                               

    1. SWEETCORN
    Maize            USA         25% EC        1101         110-720           8          0-4 days        <0.01        0.05    0.02(6)    Ussary,
    (Zea mays)      1976-8                                  during                                                                       1978b,
    Cobs after                                210-2201      ground           7-16        0-4 days        <0.01        0.01    <0.01(13)  1979a
    Kernals                                                 applications
    Removed                                   280-450       or 30-135        6-13        0-4 days        <0.01        0.12    0.02(11)
    [code no.                                               during
    A03.1604]                                               aerial
                                                            applications

    Husks           Canada       25% EC       62.5-70       280-1550         2-7         1-7 days         0.06        0.35    0.27(10)   Chipman,
    [code no.       1975-7       50% EC                                                  30-46 days       <0.01       0.33    0.17(2)    Inc.,
    A03.1604]                                 100-1051                       1-4         1-14 days        <0.01       0.35    0.23(13)   1978;
                                                                                         30-43 days       <0.01       0.26    0.10(3)    Ussary,
                                              140-1501                       3-5         3-7 days         0.34        0.36    0.35(2)    1978b,
                                                                                         46 days                              0.02(1)    1979a
                    USA          25% EC       210-2201      110-720          7-8         0-3 days         0.43        14      6.4(7)
                    1976-8                    280-335                        6-9         0-14 days        1.0         18      3.7(10)

    Stover          USA          25% EC         1101        270-600           8          0-4 days         0.99        18      7.2(6)     Ussary,
    [code no.       1976-9                                  during                                                                       1978b,
    A03.1604]                                 210-2201      ground           7-8         0-3 days         2.5         23      14(8)      1979a
    (all data                                             applications
    on 24% dry                                280-450       or 30-35         6-16        0-14 days        4.6         29      17(12)
    matter basis)                                           during
                                                            aerial
                                                          applications
                                                                                                                                               
    1 Indicates effective use rates.  For use patterns on these crops, see Table 1.
    Figures in parentheses are the numbers of results upon which the means are based


    TABLE 6.  Permethrin Residues In Treated Wheat and Sorghum In Concrete Silos
    (Australian Large-Scale Post-Harvest Treatments)

    Wheat Data1

                                                                                                                                               
               Grain conditions        Amount                                           Residues (mg/kg)
          % moisture   air temp.   Applied (calc'd)                                Period of storage (months)
                         C2            mg/kg           1         2        3        4         5          6         7         8      9      15
                                                                                                                                               
    range    8-12        14-35       0.94-1.15      0.70-0.90 0.65-0.83 0.6-0.8 0.70-0.78 0.75-0.80  0.50-0.80 0.75-0.80 0.63-0.65 0.57 0.60-0.70
    mean                                0.99           0.83   0.75        0.70    0.74       0.74       0.66     0.78       0.64   0.57   0.65
    s.d.                                               0.17     -         0.06      -          -        0.14       -          -      -       -
    c.v.3                                               21      -         9         -          -         21        -          -      -       -
                                                                                                                                               

    (Bengston et al, 1979a,b; Desmarchalier et al, 1979)


    1 Trials included treatment of 30 tonnes of barley apart from some 10,500 tonnes wheat.
    2 Initial temperatures were in the range 25-33C, at 6 months they were 14-27C, at 8 months they were 17-22C.  Initial moisture contents were
    in the range 9-12%, at 6 months they were 8-12% and at 8 months they were 9-11%.  Data are from 1977/78 and 1978/79 large scale trials.  Grain
    stored in 16 silos (30-1400 tonnes grain) in 5 Australian States.
    3 s.d. = standard deviation; c.v. = co-efficient of variation.

    Sorghum Data1

                                                                                                                       
                 Grain Conditions             Amount                               Residues (mg/kg)
           % moisture2  air temps. C2    Applied (calc'd)                   Period of Storage (months)
                                               mg/kg            1           6          12          17          26
                                                                                                                       
    range       11.6         21.2              1.06         0.70-0.80   0.56-0.58  0.62-0.71   0.56-0.57   0.53-0.62
    mean                                                       0.75       0.57        0.67        0.57        0.58
                                                                                                                       

    (Bengston et al, 1979c)


    1 Data from grain stored in a silo (430 tonnes) at one site.  1978 trial.
    2 Initial

    TABLE 7.  Residues Of Cis And Trans Isomers Of Permethrin In Stored Grain
    Percentage Proportions In Stored Wheat And Sorghum

                                                                                                                     
                        Storage Conditions          Original                           % Residues
                   % moisture   air temps. C1     proportion                   Period of Storage (weeks)
                                (nominal)                         1        6        13      17      20     26     39
                                                                                                                     

    wheat                                                         37       36      35.5     -      38.3   38.8   36.3
    cis                10            32               40          63       64      64.5     -      61.7   61.2   63.7
    trans                                             60

    sorghum
    cis                11.6          21.2             25          20.7     24.6    22.5    21.2      -     21
    trans                                             75          79.3     75.4    77.5    78.8      -     79
                                                                                                                     

    (Simpson, 1979)

    1 Initial
    


    Ectoparasite uses

    Cows were given five whole-body sprays of permethrin at a rate of 1.0
    g ai/cow, with 14 days between sprays, using a 5% emulsifiable
    concentrate formulation.  They were allowed free access to a
    self-oiler containing a 0.03 g ai/l solution, ensuring at least two
    applications per day for a period of ten weeks, and were housed in
    premises that were sprayed at a rate of 0.06 g ai/m2,  five sprays
    taking place with a 14-day interval between sprays, cows having free
    access to the premises during spraying.  This degree of exposure is at
    the highest end of the range that is likely to occur in normal
    husbandry practice.  Milk samples were taken for analysis before, and
    during the ten days after, the fifth application.  Only four out of 70
    samples of milk analyzed showed any measurable residues of permethrin
    or its metabolites cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethyl
    cyclopropane carboxylic acid (DCVA), 3-phenoxybenzoic acid (3-PBAcid)
    and 3-phenoxybenzylalcohol (3-PBAlc) (Figure 1) (Table 8) (Ussary and
    Braithwaite, 1980a).

    TABLE 8.  Residues of Permethrin And Metabolites In Milk Following
    Five
    Dermal Applications Of Permethrin At 1.0 g ai/cow

                                                                      
                    Time after    Lowest       Highest     Mean
    Chemical        application   Residue      Residue     Residue
                      (days)      (mg/kg)      (mg/kg)     (mg/kg)
                                                                      

    Permethrin           0         <0.01        0.01       0.01 (20)1
                         1         <0.01        0.01       0.01 (10)
                        3-7        <0.01        <0.01      <0.01 (30)
                         10        <0.01        0.01       0.01 (10)
    DCVA (I+II)         0-10       <0.01        <0.01      <0.01 (70)
    3-PBAcid (IV)       0-10       <0.01        <0.01      <0.01 (70)
    3-PBAlc (III)       0-7        <0.01        <0.01      <0.01 (60)
                         10        <0.01        0.02       0.01 (11)
                                                                      

    1 Bracketed figures are numbers of samples

    Ussary and Braithwaite, 1980a


    Cows were given 6 whole-body sprays of permathrin at a rate of 1.0 g
    ai/cow with 14 days between sprays.  They were allowed free access to
    a self-oiler containing a 0.03 g ai/l solution ensuring at least two
    applications per day for a period of ten weeks and were housed in
    premises which were sprayed at a rate of 0.06 g ai/m2, six sprays
    taking place with a 14-day interval between sprays, cows having free
    access to the premises during spraying.  This degree of exposure is at
    the highest end of the range which is likely to occur in normal

    husbandry practice.  Cows were slaughtered five days after the sixth
    application, when permathrin levels in muscle, liver and the kidneys
    were low (<0.01 mg/kg).  The highest levels of permethrin were 0.10
    mg/kg and 0.04 mg/kg in the intestinal and subcutaneous fat
    respectively (Table 9) (Ussary and Braithwaite, 1980b).

    TABLE 9.  Residues Of Permethrin In Tissues of Cows Following Dermal
    Applications

                                             

    Tissue            Permethrin Residue1
                            (mg/kg)
                                             
    Muscle                  <0.01
    Kidney                  <0.01
    Liver                   <0.01
    Intestinal fat        0.05-0.10
    Subcutaneous fat      0.03-0.04
                                             

    1 Limit of determination: 0.01 mg/kg   (Ussary and Braithwaite,
    1980b)


    Pigs were housed in premises treated with mist applications of 0.06 g
    permethrin per m3 at 14-day intervals and slaughtered one day after
    the sixth application.  Permethrin residues were not measurable in
    skin, liver or kidney tissues (limit of determination: 0.01 mg/kg) and
    only low levels of permethrin were found in the fat and muscle tissues
    (0.02 and up to 0.01 mg/kg respectively) (Table 10) (Ussary and
    Braithwaite, 1980c).

    TABLE 10.  Residues of Permethrin Detected in Swine Tissues after Six
    Mist Applications of Permethrin to Swine Premises at O.O6 g per m2

                                           
    Tissue            Permethrin Residues
                            (mg/kg)
                                           
    Skin                    <0.01
    Muscle                  <0.01
    Liver                   <O.01
    Kidney                  <0.01
    Subcutaneous fat         0.02
    Intestinal fat           0.02
                                           
                                       (Ussary and Braithwaite, 1980c)


    Hens were present at the times of application when premises received
    six mist applications of 0.06 g permethrin per m3 at 14-day
    intervals. Eggs were collected at intervals up to 50 days following

    the first application and hens were sacrificed five days after the
    sixth application.  Eggs were found to contain permethrin at 0.02
    mg/kg on one occasion only.  Otherwise, permethrin residues in muscle,
    skin, liver and eggs were below 0.01 mg/kg.  A residue of 0.02 mg/kg
    was detected in fat tissues (Table 11) (Ussary and Braithwaite,
    1980d).

    TABLE 11. Residues of Permethrin in Eggs and Tissues Chickens
    Maintained in Premises Treated with Permethrin

                                   
    Tissue            Permethrin
                       (mg/kg)
                                   
    Muscle             <0.01
    Skin               <0.01
    Liver              <0.01
    Fat                 0.02
    Eggs               <0.02
                                   
                                       (Ussary and Braithwaite, 1980d)


    FATE OF RESIDUES

    In the text which follows, reference will be made to various sites of
    radiolabelling of permethrin.  These will refer to 14C-labelling as
    shown in Figure 2.

    In farm animals

    Introduction

    Data on absorption, excretion and accumulation after oral dosing of
    permethrin were reviewed at the 1979 Meeting (FAO/WHO, 1980). 
    Permethrin is extensively metabolised and rapidly excreted by cows and
    goats after oral administration.  Residue levels in milk, muscle and
    fat are small, as they are in the skin, muscle and eggs of hens.
    Permethrin itself constitutes more than half of the residue in milk,
    eggs and fat, and in the muscle of livestock.  In all cases, residue
    levels decline notably on cessation of exposure.

    After dermal application the majority of the small residues detected
    are found in the tissues, at or immediately below the site of
    application.  At least 70% of the total residue in those tissues is
    due to permethrin itself.  Residues in milk and eggs reach a peak a
    few days after dermal application and then decline rapidly.

    FIGURE 3

    Cows and goats

    When cows received a single oral dose of 40:60 cis:trans
    14C-labelled permethrin (either cyclopropyl- or methylene-labelled)
    at 2.5 mg/kg bodyweight, equivalent to approximately 80 mg/kg in the
    diet, levels of radioactivity in milk reached a maximum of 0.13 mg
    permethrin equivalents/kg after 1-2 days.  These declined to less than
    0.02 mg/kg after seven days.  Levels of radioactivity in the fat were
    0.12-0.18 mg permethrin equivalents/kg, after seven days.  By fourteen
    days these had declined to 0.05-0.06 mg/kg, indicating that the small
    residues in fat are also not maintained on cessation of dosing (Bewick
    and Leahey, 1976).

    Hunt and Gilbert dosed goats orally with either the cis- or
    trans-isomers of 14C-labelled permethrin (carbonyl- or
    methylene-labelled) at a rate equivalent to approximately 6 mg/kg in
    the diet for ten days.  Total radioactive residues in the milk reached
    a plateau after three days of 0.02-0.05 and <0.01-0.01 mg permethrin
    equivalents/kg respectively for the cis- and trans- isomers.  The
    goats were sacrificed 24 hours after receiving the final dose, when
    levels of radiocarbon in meat tissues were as shown in Table 12. 
    Total radioactivity in the fat of animals receiving the cis-isomer
    was ten times higher than in those receiving the more readily
    hydrolysed trans-isomer (Table 12) (Hunt and Gilbert, 1977).

    When cis- and trans-isomers of 14C-labelled permethrin (carbonyl-
    and methylene-labelled) were administered orally to lactating Jersey
    cows for three consecutive days at approximately 1 mg/kg bodyweight,
    radioactivity was largely eliminated from the body in faeces and urine
    within 12 or 13 days after the initial treatment.  Total
    14C-permethrin equivalents in milk were consistently below 0.3 mg/kg
    and declined on cessation of exposure.  Residues in fat were also low. 
    Residues recovered from fat and milk were higher when cis-
    permethrin rather than trans-permathrin was administered and
    consisted almost entirely (>85%) of unmetabolised permethrin.

    Total 14C-permethrin equivalents in blood reached a transient peak
    shortly after each dose and dropped to insignificant levels within 2-4
    days after the last dose (Gaughan et al, 1976, 1978a).

    A study with non-radiolabelled permethrin supported the finding that
    permethrin itself is the predominant residue in milk.  It was also the
    major residue in cow muscle.  In this study, groups each of three
    barren Friesian cows, yielding 9-13 litres of milk per day, were
    maintained on diets containing permethrin at approximately 0.2, 1.0,
    10 or 50 mg/kg.  The permethrin was absorbed on grass nuts.  After
    28-31 days two cows in each group were sacrificed.  The third was
    returned to control diet for nine days before sacrifice.  Samples of
    milk and of meat tissues were analyzed for residues of permethrin,
    cis and trans 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane
    carboxylic acids (I and II, DCVA) taken together,
    3-phenoxybenzylalcohol (III; 3-PBAlc) and 3-phenoxybenzoic acid (IV;
    3-PBAcid) (Figure 1) by the gas chromatographic methods reviewed under
    "Methods of Residue Analysis".



        TABLE 12.  Total Radio-labelled Residues In Tissues of Goats Receiving 14C-Labelled Permethrin
    Daily Orally For 7-10 Days

                                                                                                            
    Material           Dose Level   Duration of     Period Between     Total Residue (mg permethrin
    Administered       (= mg/kg    Administration   Last Date And       equivalents/kg In
                       in diet)        (days)       Sacrifice          Fat     Muscle      Liver      Kidney
                                                                                                            

    Permethrin,           10             7             4 hours       <0.01    <0.014    0.12-0.34   0.31-0.41
    40:60 cis-trans

    Permethrin,           6             10            24 hours     0.01-0.03  <0.01     0.01-0.04     0.03
    trans-isomer

    Permethrin,           6             10            24 hours     0.22-0.25  <0.01     0.12-0.13     0.05
    cis-isomer
                                                                                                            

    Hunt and Gilbert, 1977
    Leahey et al, 1977a

    TABLE 13.  Characterisation of 14C-Labelled Residues In Liver And Kidney Of Goats
    Receiving Permethrin Orally Daily For Seven Days

                                                                                                            
                                                             Radioactivity Soluble in Water

                                           % Of        % of Radioactivity   % of Radioactivity
    Organ       Position of           Radioactivity    Soluble in Diethyl     Remaining Water     Unextracted
                14C-Labelling         Soluble in       Ether Following        Soluble After
                Of Permethrin         Diethyl Ether    Hydrolysis             Hydrolyais
                                                                                                            

    Liver    Methylene ("Alcohol")         16                  41                   23              note 1
             Cyclopropyl ("Acid")          39                  24                   36              note 1
    Kidney   Methylene ("Alcohol")         43                  42                   <1                 6
             Cyclopropyl ("Acid")          29                  20                   22                 9
                                                                                                            

    1 liver was almost completely solubilised during refluxing.                     

    Leahey et al, 1977a
    


    Only permethrin itself was detected in milk.  Low levels of 0.01-0.06
    mg/kg (mean 0.02 mg/kg) and 0.03-0.2 (mean 0.1 mg/kg) were present in
    the milk of cows in the 10 and 50 mg/kg groups respectively.  These
    values are approximately 0.2% of the corresponding dietary levels.
    Permethrin residues in milk were less than 0.01 mg/kg at the 0.2 and
    1.0 mg/kg dietary inclusion rates.  None of the three metabolites was
    found in any of the milk samples analyzed (limit of determination:
    0.01 mg/kg).  Permethrin levels in milk did not accumulate over the
    period of the study and they declined rapidly, to below 0.01 mg/kg
    after five days, on returning the animals to control diet (Edwards and
    Iswaren, 1977; Swaine et al, 1980a).

    Permethrin itself was also the major part of the small residue levels
    found in adductor, pectoral and cardiac muscle.  These small levels
    were approximately 0.1% of the corresponding dietary inclusion levels
    (Table 14).  Permethrin residue levels in peritoneal fat were
    invariably higher than in subcutaneous fat (Table 15) (Edwards and
    Iswaren, 1977; Swaine et al, 1980a).

    As found separately by Leahey et al (below), metabolites rather than
    permethrin itself constituted the major part of the residues in liver
    and kidney.  Again, the levels declined rapidly on cessation of
    exposure (Table 14) (Edwards and Iswaren, 1977; Swaine et al,
    1980a).

    Leahey et al dosed goats orally with 40:60 cis:trans 14C-
    labelled permethrin (cyclopropyl or methylene-labelled) at a rate
    equivalent to approximately 10 mg/kg in the diet for seven days. 
    Total radioactive residues in the milk reached a plateau of 0.02-0.03
    mg permethrin equivalents/kg after five days; 30-50% of this
    radioactivity was associated with the butterfat fraction of the milk,
    in which total radioactive residues were 0.13-0.27 mg permethrin
    equivalents/kg.

    The animals were sacrificed four hours after receiving the final dose,
    when levels of radiocarbon in meat tissues were as shown in Table 12.
    Characterization of the residues in liver and kidney, the two tissues
    containing the highest total residues is shown in Table 13.  Where
    "alcohol"-labelled permethrin was used, approximately 70% of the 14C
    in kidney tissue was 3-phenoxybenzoic acid (IV) plus
    3-(4'-hydroxyphenoxy) benzoic acid (VI) (Figure 1).  Approximately 30%
    of the 14C in the liver was due to 3-phenoxybenzyl alcohol (III) plus
    3-(4'-hydroxyphenoxy) benzyl alcohol (V).  A further 15% was due to
    3-phenoxybenzoic acid (IV) plus 3-(4'-hydroxyphenoxy) benzoic acid
    VI).  Where "acid"-labelled permethrin was used, approximately 10-15%
    of the label in liver and kidney was due to the cis and trans
    3-(2,2-dichlorovinyl) cyclopropane carboxylic acids (I and II)
    (principally the trans isomer). (Leahey et al, 1977a).



        TABLE 14.  Residues Of Permethrin and Three Major Metabolites in Tissues Of Cows
    Receiving Permethrin In The Diet

                                                                                                         
    Nominal     Residue (mg/kg)     Of
    Dietary     Feeding Regime    Tissue
    Inclusion                     Analysed                     Cis & Trans
    Level                                      Permethrin         DCVA           3-PBAlc       3-PBAcid
    (mg/kg)                                                     (I and II)        (III)          (IV)
                                                                                                         
    50          "Treated"1        Liver          <0.01          0.01-0.04       0.05-0.10      0.03-0.12
                                  Kidney        0.02-0.06       0.07-0.09       0.01-0.09      0.03-0.04
                                  Muscle        O.03-0.10       <0.01-0.02       <0.131          <0.01
                "Treated plus     Liver          <0.01             0.01           <0.01          <0.01
                 Recovery"2       Kidney          0.02             0.06           <0.01          <0.01
                                  Muscle        0.02-0.06         <0.01           <0.01          <0.01
    10          "Treated"         Liver          <0.01            <0.01         0.01-0.03      0.01-0.02
                                  Kidney       <0.01-0.01       <0.01-0.02     <0.01-0.01      <0.01-0.02
                                  Muscle       <0.01-0.03         <0.01           <0.01          <0.01
                "Treated plus     Liver          <0.01            <0.01           <0.01          <0.01 
                 Recovery         Kidney          0.01            <0.01           <0.01           0.04
                                  Muscle        0.01-0.02         <0.01           <0.01          <0.01
    1.0         "Treated"         Liver          <0.01            <0.01           <0.01          <0.01
                                  Kidney         <0.01            <0.01           <0.01        <0.01-0.01
                                  Muscle         <0.01            <0.01           <0.01          <0.01
                "Treated plus     Liver          <0.01            <0.01           <0.01          <0.01
                 Recovery"        Kidney          0.01            <0.01           <0.01           0.02
                                  Muscle         <0.01            <0.01           <0.01          <0.01
    0.2         "Treated"         Liver          <0.01              -               -              -
                                  Kidney         <0.01              -               -              -
                                  Muscle         <0.01              -               -              -
                "Treated plus     Liver          <0.01              -               -              -
                 Recovery"        Kidney          0.01              -               -              -
                                  Muscle         <0.01              -               -              -
                                                                                                         
    1 "Treated" indicates the animals received treated diet for 28-31 days and were then slaughtered.
    2 "Treated plus Recovery" indicates the animals received treated diet for 28 days and were then
    returned to untreated diet for a further 9 days before slaughter.

    Edwards and Iswaren, 1977; Swaine et al, 1980a
    


    TABLE 15.  Residues In Fat Of Cows Receiving Permethrin In The Diet

                                                                
    Nominal                Residues (mg/kg) of Permethrin In
    Dietary Inclusion                                           
    Level (mg/kg)         Peritoneal Fat     Subcutaneous Fat
                                                                

    0.2                   <0.01-0.04             <0.01
    1.0                    0.01-0.02              <0.01
    10                     0.02-0.25              <0.01-0.09
    50                     0.46-1.1                0.10-0.42
                                                                

                                       (Edwards and Iswaren, 1977)


    TABLE 16.  Total Radiolabelled Residues In Tissues Of Cows Seven Days
    After Receiving A Single Dermal Dose Of 1.25 g of 40:60 Cis:Trans
    14C-Labelled Permethrin

                                                                     
    Tissue              Residue in tissue       Residue in tissue
                        from cow treated        from cow treated
                        with alcohol-labelled   with acid-labelled
                        permethrin, mg/kg1      permethrin g/kg1
                                                                     
    Meat                     <0.01                   <0.01
    Subcutaneous fat          0.053                   0.033
    Perirenal fat             0.046                   0.054
    Liver                     0.080                   0.064
    Kidney                    0.048                   0.038
                                                                     

    1 Residues expressed as mg/kg permethin equivalents.  Bewick et al,
    1977.


    Permethrin itself also constitutes the major part of the small
    residues found in the milk and fat of cows after dermal application.

    In one study, cows received a single dermal dose of 40:60
    cis:trans 14C-labelled permethrin (cyclopropyl- or
    methylene-labelled).  Although the concentration of suspension used
    (0.5% w/v) was ten times the maximum that is likely to be used in
    practice, the total dose of 40 mg per cow was approximately 1/30 of
    the amount that could be applied commercially at any one time.  The
    dose was placed on an area of 225 cm2.

    Levels of radioactivity in the milk and blood reached a maximum during
    the first few days after dosing and then declined steadily.  Total
    residues in milk were always less than 2 g permethrin equivalents/kg

    (i.e. less than 2 ppb) and were below the limit of determination (0.3
    g/kg) by the end of fourteen days following treatment.

    Total radiolabelled residues in muscle, liver, kidney and heart were
    also small - 0.02 mg permethrin equivalents/kg or below seven days
    after treatment - and were considerably smaller after a further seven
    days.

    Highest residues were found in fat from below the treatment area.
    Seven days after treatment the total residue was approximately 0.5 mg
    permethrin equivalents/kg, of which at least 80% was due to permethrin
    itself.  After a further seven days, residues in fat below the site of
    application had fallen by about one half; the residue remaining was
    again characterised as being due mainly to permethrin itself (Bewick
    and Leahey, 1976).

    In a second study, cows received a single dermal dose of 40:60
    cis:trans 14C-labelled permethrin (cyclopropyl- or
    methylene-labelled). The dose of 1.25 g per cow applied in a 0.5% w/v
    emulsion is at the higher end of the range likely to be used
    commercially.  The permethrin was brushed onto 25% of the surface area
    of the animals.

    Levels of radioactivity found in milk were very similar for the two
    positions of radiolabelling.  Residues reached a peak of approximately
    0.01 mg permethrin equivalents/kg after 3-5 days; 89-91% of these
    residues could be extracted into butter fat in which the major portion
    of the residue (at least 51-68%) was characterised as permethrin
    (Leahey and Cameron, 1978).

    Seven days after treatment only small residues were present in the
    animal tissues.  Levels of radioactivity were similar in perirenal and
    subcutaneous fat and for the two positions of radiolabelling (Table
    16).  At least 40% of this residue was characterised as permethrin
    (Leahey and Cameron, 1978).

    Pigs

    Pigs were dosed dermally with 40:60 cis:trans 14C-labelled
    permethrin (cyclopropyl or methylene-labelled).  Although the
    concentration of suspension used (0.5% w/v) was ten times the maximum
    that is likely to be used in practice, the total dose of 18 mg per pig
    is approximately 1/30 of the amount that could be applied commercially
    at any one time. The dose was placed on an area of 100 cm2.

    Seven and fourteen days after treatment approximately 1% of the
    applied dose remained at the site of application, principally (>95%)
    as permethrin.  A residue of 0.05 mg permethrin equivalents/kg in fat
    immediately below the site of application seven days after treatment
    was due essentially to permethrin.  After fourteen days, no
    radioactive residue was found (limit of determination: 0.012 mg
    permethrin equivalents/kg) (Bewick et al, 1977).

    A residue of 0.01 mg permethrin equivalents/kg was found in muscle
    beneath the site of application seven days after treatment. 
    Otherwise, no residues were detected in muscle, liver, kidney, heart
    or blood either seven or fourteen days after treatment (limit of
    determination: approximately 0.001 mg permethrin equivalents/kg)
    (Bewick et al, 1977).

    Hens

    In one study hens received a single oral dose of 40:60 cis:trans
    14C-labelled permethrin (cyclopropyl- and methylene-labelled) at a
    rate equivalent to 30 mg/kg in the diet.  Birds were sacrificed one,
    seven and fourteen days after treatment.

    Throughout the study, residues in breast muscle, leg muscle and heart
    were small (less than 0.04 mg permethrin equivalent/kg).  Total
    radioactive residues in liver and kidney of 0.22-0.25 mg/kg had
    decreased by an order of magnitude after seven days.  Residues of
    0.20-0.35 mg permethrin equivalents/kg in peritoneal and subcutaneous
    fat on the day after treatment also declined during the remainder of
    the study, albeit more slowly than in the case of liver and kidney
    (Leahey et al, 1977c).

    Levels of radioactivity in eggs reached a maximum soon after dosing
    (in 1-4 days) and then declined during the remainder of the 14-day
    study (Leahey et al, 1977c).

    Hens have also been dosed orally with 40:60 cis:trans
    14C-permethrin (cyclopropyl- or methylene-labelled) for ten days at a
    rate equivalent to approximately 10 mg/kg in the diet or separately
    with cis- and trans-isomers (carbonyl- or methylene-labelled) for
    three days at a rate equivalent to approximately 80 mg/kg in the diet. 
    Residues in eggs were present primarily (>75%) in the yolks, in which
    radioactivity reached a plateau after 5-8 days of 0.3-0.5 mg
    permethrin equivalents/kg in the 10-dose study and 0.6 mg/kg (trans-
    isomer administered) or 2.1-2.8 mg/kg (cis-isomer administered) in
    the 3-dose study.  Permethrin was the major compound identified in the
    eggs (52-62%).  The cis- and
    trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic
    acids (I and II) and 3-phenoxybenzyl alcohol (III) (Figure 1) were the
    major metabolites in eggs, each normally accounting for less than
    approximately 10% of the total radioactivity.  The carboxylic acids
    were present both free and as the glucuronide and taurine conjugates.
    Other metabolites arose from hydroxylation in the 4'-position of the
    "alcohol" moiety and in the trans-2-methyl moiety in the "acid" part
    of the molecule.

    The hens were sacrificed four hours after receiving the final dose in
    the 10-dose study, when residues were as shown in Table 17.  As in the
    case of eggs, residues in fat derived from both "acid" and "alcohol"
    labels were similar.  Permethrin itself represented the major residue
    in the fat.  Compounds I-III and 3-phenoxybenzoic acid (IV) were also

    identified (each less than 10% of the total radioactivity in the fat).
    In both muscle and liver, higher residues were detected in hens dosed
    with "acid"-labelled permethrin than with "alcohol"-labelled.  The
    cis- and trans-3-2,2-dichlorovinyl)-2,2-dimethylcyclopropane
    carboxylic acids (I and II) were the major residues identified in
    these tissues.  Blood levels declined rapidly during the first 24
    hours after administration (Gaughan et al, 1978b; Leahey et al,
    1977b).

    In a study with non-radiolabelled 40:60 cis:trans permethrin,
    groups of 40 laying hens were fed on diets containing approximately
    0.4, 3.4 and 33 mg/kg for 28 days and then returned to a control diet
    for an additional 14 days.  Samples of eggs laid during the study were
    analyzed for permethrin residues by the gas chromatographic method
    described under "Methods of Residue Analysis".  Five hens per group
    were sacrificed after 21, 28, 35 and 42 days of the study and tissues
    analyzed for permethrin.

    At the 0.4 mg/kg dietary inclusion rate no residues of permethrin were
    detected on the albumen and yolks of eggs (limit of determination:
    0.02 mg/kg) or in the muscle, skin and liver (limit of determination:
    0.01 mg/kg).  At the higher dietary inclusion rates no permethrin was
    detected in egg albumen.  In yolks, permethrin residues were up to
    0.05 mg/kg and up to 0.64 mg/kg respectively at the 3.4 and 33 mg/kg
    treatment levels.  Residues did not accumulate and declined rapidly
    when feeding finished, reaching non-detectable levels (less than 0.02
    mg/kg) before the end of the 14-day recovery period in both cases.
    Only small residues (< 0.03 mg/kg) of the metabolites I-IV were found
    in eggs during the feeding period.  Again these declined on cessation
    of exposure.  At the 3.4 mg/kg dietary inclusion rate, permethrin
    residues in muscle, skin and liver were non-detectable; i.e. less than
    0.01 mg/kg.  At the 33 mg/kg rate permethrin residues in liver were
    also non-detectable. Permethrin was the major constituent of the low
    residues in muscle and skin; levels of 0.05-0.08 mg/kg fell to 0.02
    mg/kg before the end of the recovery period (Table 18) (Edwards and
    Swaine, 1977; Swaine et al, 1980b).

    Chickens have also received a single dermal dose of 40:60
    cis:trans 14C-labelled permethrin (cyclopropyl- or
    methylene-labelled).  The dose of 4.5 mg per bird, which is
    approximately 20% of the highest rate that is likely to be used
    commercially, was brushed on as a 0.1% w/v emulsion to an area between
    the rear abdomen and the end of the breast and upper leg.  Up to 29.5%
    of the applied dose was detected on skin and feathers at the site of
    application fourteen days after treatment and was still present (99%)
    as permethrin (Leahey et al, 1977).

    Total radioactive residues in liver, kidney, heart and muscle were
    low-less than 0.02 mg permethrin equivalents/kg one, seven and
    fourteen days after treatment, except in muscle below the site of
    application which contained up to 0.11 mg permethrin equivalents/kg.
    Up to 0.07 mg permethrin equivalents was found in fat at the

    application site, 70-88% of the radioactivity in subcutaneous muscle
    and fat at the site of application was characterised as permethrin
    itself (Leahey et al, 1977c).

    Radioactive residues in eggs were all below 0.03 mg permethrin
    equivalents/kg, reaching a peak 3-6 days after dosing and then
    declining progressively to below 0.01 mg/kg ten days after dosing
    (Leahey, et al, 1977c).

    When eggshells were painted with a 0.1% w/v emulsion of 40:60
    cis:trans 14C-labelled permethrin (combined cyclopropyl- and
    methylene-labelling), no radioactivity was detected in either yolks or
    albumen one, seven or fourteen days after treatment (limit of
    determination: 0.02 mg permethrin equivalents/kg) (Leahey et al,
    1977c).

    On Processing

    The fate of permethrin residues during the processing of cotton,
    soybeans, apples, pears, grapes and tomatoes was reviewed at the 1979
    Meeting.  Residues in the seeds of cotton and beans of soya, and in
    their respective processing fractions used in animal feeds, are small
    (e.g. well below 0.5 mg/kg) (FAO/WHO, 1980).

    Residues in dried apple pomace were 25-30 times the levels in
    corresponding whole apples.  No residues were determined in apple
    juice and apple sauce (limit of determination: 0.01 mg/kg) (Table 19)
    (Ussary, 1977a, c).

    Residues in wet tomato pulp, which typically contains 25% dry matter,
    were in the range 10-50 (mean 25) times the levels in whole tomatoes
    (Table 20) (Ussary, 1977d).

    During the processing of treated whole wheat grain the permethrin
    residue is retained mainly in the bran component although a
    significant proportion (12%) remains with the white flour and follows
    through almost unchanged into bread (Simpson, 1979).

    Permethrin residues in flour from treated whole grain are carried over
    into bread baked from that flour.  There is no reduction in residue
    level on a commodity-weight basis.  White flour retains about 12% of
    the whole grain residue.  The major part (about 62%) of the residue
    remains with the bran while about 26% is in the pollard.  Therefore,
    whilst white bread prepared from treated grain would have a residue of
    about 0.15-0.2 mg/kg, the corresponding level in wholemeal bread would
    be about 0.7-1 mg/kg (Table 21) (Simpson, 1979).


        TABLE 17.  Total Radioactive Residues In The Tissues of Hens Receiving
    Consecutive Daily Oral Doses Of 14C-Labelled Permethrin

                                                                                                                       
                                        Rate           No. of   Period Between   Residue (mg permethrin equivalents/kg)
    Material Administered        (expressed as mg/kg   Daily    Last Dose And                      In
                                 equivalent in diet)   Doses      Sacrifice       Fat      Muscle     Liver     Kidney
                                                                                                                       

    40:60 cis:trans-permethrin
    (cyclopropyl-lablled)                10             10         4 hours      0.5-0.6   0.07-0.13   0.9-1.1    N/D.1
    (methylene-labelled)                 10             10         4 hours      0.3-0.7      0.03       0.4      N/D1

    trans-permethrin
    (carbonyl-labelled)                  80              3         6 days         0.21      <0.06      0.14      0.31
    (methylene-labelled)                 80              3         6 days         0.18      <0.06      0.08      0.24

    cis-permethrin
    (carbonyl-labelled)                  80              3         6 days         1.0        0.06     0.27       0.34
    (methylene-labelled)                 80              3         6 days         1.4       <0.06     0.20       0.25
                                                                                                                       


    1 N/D indicates not determined.


    Gaughan et al, 1978b; Leahey et al, 1977b
    

        TABLE 18.  Residues Of Permethrin And Three Major Metabolites In Eggs And Tissues
    Of Hens Receiving Permethrin In The Diet Up To 28 Days

                                                                                                
    Dietary     Feeding Regime    Product                   Residue (mg/kg) of
    Inclusion                     Analysed
    Level                                                    Cis & Trans
    (mg/kg)                                    Permethrin       DCVA         3-PBAlc    3-PBAcid
                                               (I and II)       (III)         (IV)
                                                                                                

    33           "Treated"1       Muscle        0.05-0.08     0.01-0.02       <0.01       <0.01
                                  plus skin
                                  Liver           <0.01      <0.01-0.03       <0.01       <0.01
                                  Eggs            <0.6       <0.01-0.03     <0.01-0.03    <0.01

                 "Treated plus    Muscle          0.02           <0.01         <0.01      <0.01
                  Recovery"2      plus skin
                                  Liver           <0.01          <0.01         <0.01      <0.02
                                  Eggs            <0.02          <0.01      <0.01-0.02    <0.01

    3.4          "Treated"        Muscle          <0.01            -             -          -
                                  plus skin
                                  Liver           <0.01            -             -          -
                                  Eggs            <0.08            -             -          -
                 "Treated plus    Muscle          <0.01            -             -          -
                  Recovery"       plus skin       <0.01            -             -          -
                                  Liver           <0.01            -             -          -
                                  Eggs            <0.03            -             -          -

    0.4          "Treated"        Muscle          <0.01            -             -          -
                                  plus skin
                                  Liver           <0.01            -             -          -
                                  Eggs            <0.05            -             -          -
                 "Treated plus    Muscle          <0.01            -             -          -
                  Recovery"       plus skin
                                  Liver           <0.01            -             -          -
                                  Eggs            <0.01            -             -          -

                                                                                                

    1 "Treated" indicates the animals received treated diet for up to 28 days and
    were then slaughtered.
    2 "Treated plus Recovery" indicates the animals received treated diet for 28
    days and were then returned to untreated diet for up to 14 days before slaughter.

    Edwards and Swaine, 1977;
    Swaine et al, 1980b
    
        TABLE 19.  Permethrin Residues In Commercial Fractions Of Apples: USA: 1976

                                                                                             
    Volume of       Number of      Interval         Fraction       Permethrin Residues
    Spray          Applications    Between Last                    (mg/kg) after Applying
    Applied                        Spraying and                    at Stated Rates of mg/kg
    (l/ha)                         Harvest                         ai in spray
                                                                     80 mg/kg     160 mg/kg
                                                                                             

    3150-3600         3-5          38-63 days       Mature          0.11-0.40       0.85
                                                    apples
                                                    Juice           <0.01          <0.01
                                                    Apple           <0.01            -
                                                    Sauce
                                                    wet             0.74-3.2         6.5
                                                    pomace
                                                    Dry             3.3-10           22
                                                    pomace
                                                                                             

    Ussary, 1977a, c
    


        TABLE 20.  A Comparison Of Permethrin Residues In Processed Tomato Fractions : USA : 1977

                                                                                                    
    Rate of        Number of       Interval                  Permethrin Residues (mg/kg) In
    Application    Applications    Between Last
    (g ai/ha)                      Application      Whole       Tomato    Tomato   Tomato     Tomato
                                   And Harvest      Tomatoes    Juice     Puree    Ketchup    Pulp
                                                                                                    

       220             2              1 day           0.05      <0.01     0.01     0.01       1.08
                                      3 days          0.08       0.01      0.02     0.01       0.86
                                      7 days          0.04       0.01      0.03     0.02       1.97
       440             2              1 day           0.05      <0.01     0.03     0.02       1.60
                                      3 days          0.05       0.01      0.03     0.02       1.45
                                      7 days          0.08      <0.01     0.02     0.01       1.28
                                                                                                    

    Ussary, 1977d
    
    TABLE 21.  Distribution Of Permethrin Residues In Whole Wheat
    Fractions And Consequent Residue Levels In Bread

    Distribution of residue between whole grain fractions1

                                                                    
                                  Permethrin Residue
    Fraction           % whole grain   mg/kg     % distribution
                                                                    

    Flour (white)           75.1       0.13           12.1
    Pollard                 11.3       1.9            26.3
    Bran                    13.6       3.7            61.7
                                                                    

    Residue in Bread baked from the ground flour

                                                         
    Commodity               Permethrin residue (mg/kg)
                                                         
    White flour                     0.13-0.15
    White bread                     0.13-0.19
    Wholemeal flour2              0.81-0.93
    Wholemeal bread                 0.67-1.00
                                                         

    1 Grain sample 1.5 kg.  It had a residue level of 0.65 mg
    permathrin/kg after being stored for 9 months.
    2 Reconstituted from the fractions in the original whole grain
    proportions.

    Simpson, 1979


    The processing operations simulated those used in commercial practice,
    the unbaked bread recipe included potassium bromate and benzoyl
    peroxide.

    Wholemeal flour was formulated after reconstituting the wheat
    fractions in the original ratio.


    METHODS OF RESIDUE ANALYSIS

    The preferred method of residue analysis (by gas chromatography using
    an electron capture detector) for crops treated pre-harvest was
    reviewed at the 1979 Meeting (FAO/WHO, 1980).

    Both gas chromatography (GC) and high pressure liquid chromatography
    (HPLC) have been used to determine permethrin residues in whole cereal
    grains and commodities processed from grain (including bread).

    The GC procedure described earlier is quite suitable, being able to
    determine cis and trans isomers separately or together.  Recovery
    is essentially quantitative and the limit of determination is about
    0.01 mg/kg.

    A simple procedure based on a high pressure liquid chromatograph has
    also been developed (Simpson, 1978).  The limit of determination is a
    little better than 0.01 mg/kg.  In this procedure the residue is
    extracted by cold methanol, partitioned into hexane - and, if
    necessary, further cleaned by an acetonitrile partitioning - before
    clean-up on an alumina column.  The concentrated residue is subjected
    to determination by HPLC equipped with a UV detector.  This method is
    similar to the procedure used by Mourot et al, (1979).

    With small modifications, the GC method can be used to determine
    permethrin in milk, meat and eggs.

    Milk and meat samples are extracted with n-hexane:acetone 4:1.  The
    acetone is removed by washing with water and the permethrin
    partitioned from n-hexane into dimethylformamide.  The
    dimethylformamide extract is dissolved in 1% aqueous sodium sulphate
    and the permethrin back-extracted into n-hexane.  The hexane extract
    is cleaned up using a Florisil column, and permethrin is determined by
    gas chromatography using an electron capture detector.  The limit of
    determination of the method is 0.01 mg/kg for the combined isomers and
    recovery values for samples of meat and milk fortified at 0.01-1.0
    mg/kg are normally greater than 70%.  Mean recoveries of 89%-92% have
    been obtained from milk and 86-88% from tissues of cows and hens
    (Edwards and Iswaren, 1977; Edwards and Swaine, 1977).  Twenty percent
    acetone in hexane has been shown to be an efficient solvent for
    extracting permethrin residues from animal tissues (Edwards and
    Sapiets, 1978).

    The method for permethrin analyses in meat and milk is also applicable
    to eggs.  These are extracted with n-hexane:acetone 1:1 and the
    extract washed with aqueous sodium chloride to remove acetone, and
    cleaned up by solvent partition with dimethylformamide and by using a
    Florisil column.  The limit of determination is 0.02 mg/kg for the
    combined isomers and recovery values from yolks and albumen fortified
    at 0.01-0.4 mg/kg are generally in the ranges 70-90% and 60-90%
    respectively (Edwards and Swaine, 1977).

    The mass spectrographic technique of multiple ion detection is
    suitable for the qualitative and quantitative confirmation of
    permethrin residues in crops, milk, eggs and animal tissues following
    separation by gas chromatography.

    Qualitative confirmation of permethrin residues is given by the
    appearance of a peak at the correct retention time for all the
    specific m/e values monitored.  In addition, the ratios between the
    peak heights (or peak areas) given from each m/e value should be
    identical to that observed for permethrin analytical standards.

    Quantitative confirmation is carried out by comparison of the peak
    height or peak area, measured for the most abundant m/e value
    recorded, against those obtained with external standards of permethrin
    (Swaine and Edwards, 1977).

    Residue of both the free and conjugated major plant metabolites of
    permethrin, namely cis- and trans- isomers of
    3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (DCVA)
    and 3-phenoxybenzyl alcohol (3-PBAlc), can also be determined by gas
    chromatography.  Samples are extracted with 2:1 methanol:water and
    lipids removed by partitioning with dichloromethane.  The methanol is
    then removed using rotary evaporation, the aqueous solution made 1 N
    with HCl and refluxed to free the conjugated residues.  The residues
    are then extracted by partitioning with n-hexane.  The n-hexane is
    then removed and the 2,2,2-trichloroethyl ester of DCVA and the
    heptafluorobutyryl ester of 3-PBAlc are simultaneously made.  The
    derivatives are then analyzed by gas-liquid chromatography using
    electron capture detection.  (Ussary, 1979).  Limits of determination
    are in the range 0.02-0.10 mg/kg for DCVA and 0.02-0.05 mg/kg for 3-
    PBAlc.  Recoveries are generally in the range 70-85%.  Confirmation of
    the metabolite residues is possible using gas chromatography linked to
    mass spectrometry using multiple ion detection, similar to the
    procedure reviewed above for permethrin (Swaine et al, 1978).

    With little modification, this method has also been used to determine
    permethrin metabolite residues in meat and milk.  Meat tissues are
    extracted with 1:1 methanol:water; milk is extracted with 1:1
    hexane:acetone.  Any permethrin extracted by this procedure is
    partitioned out, along with unconjugated residues of 3-PBAlc, into
    n-hexane alone (milk) or hexane plus dichloromethane (meat). 
    Residues of 3-phenoxybenzoic acid (3-PBAcid), both "free" and
    conjugated DCVA, and conjugated residues of 3-PBAlc remain in the
    aqueous phase which is subjected to a hydrochloric acid hydrolysis to
    cleave the conjugates.  DCVA and 3-PBAcid are separated from 3-PBAlc
    by partition between aqueous sodium hydroxide and dichloromethane. 
    The PBAlc residues are combined and determined as the
    heptafluorobutyryl ester by gas chromatography using an electron
    capture detector.  DCVA and 3-PBAcid are converted to their methyl
    ester derivatives, by treatment with diazomethane, and determined by
    gas chromatography linked to mass spectrometry using multiple ion
    detection.  A limit of determination of 0.01 n/kg has been obtained
    routinely for DCVA, 3-PBAlc and 3-PBAcid in meat and milk.  Mean
    recoveries have been within the range 55-60% from milk and 60-85% from
    meat tissues (Swaine et al, 1980).

    NATIONAL TOLERANCES

    The following national tolerances were reported to the Meeting for
    permethrin (total isomers):

    Australia      Wheat Bran                    10 mg/kg

                   Raw cereals               )    5 mg/kg
                   Wheat pollard (shorts)    )

                   Brussels sprouts          )
                   Wheat flour(wholemeal)    )    2 mg/kg
                   Wholemeal bread           )

                   Broccoli                  )
                   Cabbage                   )    1 mg/kg
                   Cauliflower               )

                   Wheat flour (white)       )    0.5 mg/kg
                   White bread               )

                   Tomatoes                       0.4 mg/kg

                   Cotton                    )    0.2 mg/kg
                   Sweetcorn (cobs)          )

                   Eggs                      )    0.1 mg/kg
                   Fat of meat of cattle,    )
                   sheep, pigs and poultry   )

                   Milk and milk products    )    0.05 mg/kg
                   (fat basis)               )

    Belgium        Eggplants                 )
                   Cabbages                  )
                   Cucumbers                 )
                   Endives                   )
                   Fruit crops               )    1 mg/kg
                   Honeydew melons           )
                   Lettuce                   )
                   Peppers                   )
                   Tomatoes                  )

    France         Maize (whole plants)           0.2 mg/kg
                   Maize grains                   0.1 mg/kg

    Holland        Endives                   )    2 mg/kg
                   Lettuce                   )

                   Apples                    )
                   Brassicae                 )    1 mg/kg
                   Pears                     )

                   Eggplants                 )
                   Cucumbers                 )
                   Honeydew melons           )    0.5 mg/kg
                   Peppers                   )
                   Tomatoes                  )

    USA            Cotton                         0.5 mg/kg

                   Eggs                      )
                   Meat, fat and meat        )
                   by-products of cows,      )    0.05 mg/kg
                   goats, hogs, horses,      )
                   poultry and sheep         )

    Venezuela      Vegetables                )   10 mg/kg


    EVALUATION

    APPRAISAL

    Permethrin is a pyrethroid insecticide which is effective at low rates
    against a wide range of Lepidoptera, Hemiptera, Diptera and
    Coleoptera.  Unlike natural pyrethrins and earlier synthetic
    pyrethrins, permethrin is photostable to a degree that allows it to be
    used as an effective tool in agriculture.  It shows adulticidal,
    ovicidal and particularly larvicidal activity and is effective against
    the great majority of insects that. have become resistant to standard
    treatments such an organochlorines and organophosphates.  A programme
    of sprays is usually required.

    A particularly valuable usage is in protection of stored grain.
    Laboratory and silo-scale studies in Australia have shown that low
    levels of permethrin control most of the endemic insect pests of
    stored grain, and, when used in conjuction with a synergist and
    complementary insecticide, the commonly-occurring strains of all grain
    insect pests are controlled.  Adequate protection of at least 9 months
    storage is achieved by a single application of 1 mg permethrin/kg.
    However, for various reasons, it may become necessary in future to use
    permethrin without its synergist and/or o/p insecticide.  In that
    case, higher application rates would be required to maintain the
    present level or permethrin efficacy.  The same applies if the present
    experimental rate is increased for other reasons (e.g. to counter
    resistance).  A 2 mg/kg grain is likely to be the target concentration
    in the near future.

    Permethrin can also be used to control various ectoparasites of
    cattle, horses, sheep, pigs and poultry.  It can be applied either
    directly to the animals, or to buildings in which they are housed, or
    to insect breeding and resting sites.

    Extensive residues data are available from supervised trials.  In
    pre-harvest uses, residues are highest where a crop part is exposed
    directly to the spray, as in the case of many forage crop uses. 
    Ground and aerial applications yield similar residue levels.  Although
    residues decline comparatively slowly after spraying, there is no
    obvious build-up of residues of permethrin or of its two most
    important plant metabolites on repeated application, within the rates
    and frequency of permethrin spraying that are needed to obtain good
    insecticidal control.  The two important plant metabolites are
    3-phenoxybenzyl alcohol and the cis and trans isomers of
    3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (DCVA),
    which are also animal metabolites; levels of these metabolites in
    crops are very much smaller than corresponding permethrin residues and
    they do not need to be included in routine residue analyses.

    Permethrin levels on stored grains also decline slowly.  During the
    processing of treated whole wheat grain, the permethrin residue is
    retained mainly on the bran component, although a significant
    proportion (12%) remains with the white flour and follows through 

    After both oral and dermal administration to livestock, permethrin
    itself constitutes the major portion of the residue recovered from
    milk, eggs, muscle and fat.  After oral administration to goats,
    metabolites form the major part of the residue in kidney and liver;
    DCVA occurs in both organs, 3-phenoxybenzyl alcohol plus its
    4'-hydroxy derivative in liver and 3-phenoxybenzoic acid plus its
    4'-hydroxy derivative in liver and kidney.

    Following direct application to dairy cattle (1.0 g ai/cow and with
    free access to a self-oiler) permethrin levels are low in milk (<0.02
    mg/kg) and in muscle, liver and kidney (<0.01 mg/kg).  Highest levels
    (up to 0.1 mg/kg) have been found in fat.

    Cows maintained on a diet containing 50 mg/kg of permethrin yielded
    milk containing low levels of residue (0.1 mg/kg), and the level in
    muscle was less than 0.1 mg/kg.  The residue in milk declined to below
    0.01 mg/kg after five days on returning the cows to control diet.

    Residues in eggs are also low and contamination of eggs laid during
    the treatment of poultry houses will not result in detectable residues
    in yolks or albumen.

    Permethrin is not detected in the albumen of eggs from hens receiving
    the compound at levels up to 33 mg/kg in the diet; levels in yolks are
    approximately 2% of corresponding permethrin dietary levels.

    In all cases studied, residues of permethrin and its metabolites in
    products of animal origin declined notably on cessation of exposure.

    Only small residue levels have been found in products of animal origin
    following direct application of permethrin to livestock.  In view of
    the levels of permethrin found in forage crops, such as alfalfa, and
    the importance of such crops in animal feedstuffs, it seems likely

    that residue levels in products of animal origin will be higher
    following forage crop uses rather than from ectoparasite outlets.  In
    estimating maximum residue levels for products of animals origin,
    allowance has also to be made for the dilution effect that will occur
    in practice when treated forage is incorporated into livestock diets.

    In proposing maximum residue levels on raw grain and milled cereal
    products prepared therefrom, careful consideration has been given to
    the fact that this insecticide is to be used as a grain protectant and
    that residues of the compound are comparatively stable under storage
    conditions.  Under practical conditions of grain handling and storage,
    it is not possible to apply a grain protectant with assurance that the
    deposit will be absolutely uniform; there will always be a natural
    variation in the level of the deposit resulting from fluctuations in
    the flow of grain and of the insecticide.  Furthermore, the movement
    of bulk grain results in the segregation of the various components of
    the bulk with a resultant variation in the level of residues
    throughout the mass.  Due allowance has been for the amplitude of
    these variations and the problems of sampling and analysis.

    The meeting examined residue data from supervised storage and feeding
    trials reflecting established or proposed good practice.  From these
    data the meeting was able to estimate the maximum residue levels that 
    were likely to occur when permethrin was used in practice.

    The preferred method of permethrin residue analysis in crops is by gas
    chromatography using an electron capture detector.  Recoveries are
    essentially quantitative and the method has been applied successfully
    to a wide range of crops, raw cereal grains and processed products
    derived from them, such as flour, bran and bread.  A limit of
    determination of 0.01 mg/kg (expressed as permethrin cis and trans
    isomers). Cis and trans-isomers are capable of being determined
    separately by this method.  With small modifications, the method has
    been applied successfully to the determination of permethrin residues
    in meat, milk and eggs, and would with adaptation be suitable for
    regulatory purposes.


    RECOMMENDATIONS OF RESIDUES LIMITS

    The meeting concludes that the residue levels listed below are
    temporary pending submission of the "Further Work or Information". 
    These are recommended as suitable for establishing temporary maximum
    residue limits.  These levels are additional to those proposed by the
    1979 Meeting.  These levels refer to the sum of the cis and
    trans-isomers of permethrin.

                                                                        
    Crop                            TMRL (mg/kg)
                                                                        

    Alfalfa fodder                  100) On a dry weight basis
    Maize fodder and straw          100)
    Apple pomace                     50) On a dry weight basis

    Soybean fodder                   50) On a dry weight basis

    Cereal grains                     2
    Wheat flour (wholemeal)           2
    wheat flour (white)               0.5
    Wheat bran                       10

    Carcass meat of
         cattle  )                        For permethrins a portion of
         pig     )                    1   carcass fat is analyzed and
         sheep   )                        the levels refer to carcass fat.

    Meat by-products from:
         pigs    )                    0.1
         sheep   )

    Poultry meats                     0.1
    Eggs                              0.1
    Milk                              0.1
                                                                        


    FURTHER WORK OR INFORMATION

    Recommendations 3, 4, 8, 9 from 1979 meeting remain relevant.


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    See Also:
       Toxicological Abbreviations
       Permethrin (EHC 94, 1990)
       Permethrin (HSG 33, 1989)
       Permethrin (ICSC)
       PERMETHRIN (JECFA Evaluation)
       Permethrin (Pesticide residues in food: 1979 evaluations)
       Permethrin (Pesticide residues in food: 1981 evaluations)
       Permethrin (Pesticide residues in food: 1982 evaluations)
       Permethrin (Pesticide residues in food: 1983 evaluations)
       Permethrin (Pesticide residues in food: 1984 evaluations)
       Permethrin (Pesticide residues in food: 1987 evaluations Part II Toxicology)
       Permethrin (JMPR Evaluations 1999 Part II Toxicological)
       Permethrin (UKPID)
       Permethrin (IARC Summary & Evaluation, Volume 53, 1991)