Sponsored jointly by FAO and WHO


    Joint meeting of the
    FAO Panel of Experts on Pesticide Residues
    in Food and the Environment
    and the
    WHO Expert Group on Pesticide Residues
    Geneva, 3-12 December 1979



    Chemical Name:                   3-phenoxybenzyl

    Synonyms:                        3-2539, Wellcide (R)

    Structural Formula:              C23H26O3


    Other information on identity and properties

    Molecular weight:                350.5

    State:                           colorless liquid

    Specific gravity:                d25 1.058

    Viscosity:                       195.1 cp at 20C

                                     87.4 cp at 30C

    Vapour pressure:                 1.2  10-6 mmHg at 20c

    Refractive index:                n25 1.5483

    (g/l at room                     Highly soluble in the following solvents
    temperature)                     solvents (>500 g/l methanol, isopropanol,
                                     ethylcellosolve, diethyl ether, xylene,
                                     n-hexane alpha-methyl, naphthalene,
                                     cyclohexane, chloroform, acetonitrile,
                                     dimethyl formamide, kerosene.

    Solubility in water:             1.4  0.1 ppm at 30C

    Stability:                       No breakdown after one year at room
                                     temperature out of the light. Stable in
                                     neutral and weak acidic conditions. Stable
                                     in most solvents except methanol, ethyl
                                     cellosolve, o-cresol, dimethylsulfoxide.

    Typical percent purity of the technical material

                                                          % by weight
    3-phenoxy ()-cis, trans-chrysanthemate               92.5 - 94.5

    The meeting was also provided by the manufacturer with complete
    information on the chemical nature and quantity of the residual
    manufacturing impurities in the technical material.  This information
    is on file with the Secretariat of the meeting.  The data in this
    monograph are from phenothrin meeting these specifications as are the
    recommendations for residue limits.


    Use Pattern

    Phenothrin is a new pyrethroid being currently developed.  It is more
    stable than natural pyrethrins and other novel pyrethroids developed
    earlier, but it is relatively degradable by sunlight.  In the light of
    its insecticidal properties and its relatively low toxicity to
    mammals, phenothrin and its optically active isomers show much promise
    as a safe and useful insecticide in various fields including
    households, public health, food storage, ornamentals and livestock

    Principal uses currently are:

    1.  in household aerosols and sprays formulated in combination with
        tetramethrin, piperonyl butoxide, carbamates and/or fenitrothion
        for control of various species of plant hoppers and for control of
        house-flies, mosquitoes, cockroaches and other household or public
        health insect pests.

    2.  in grain protection and disinfestation.

    Treatment of plants

    Repeated and multiple applications of organophosphorus compounds (e.g.
    malathion) and carbamates (e.g. carbaryl) for control of green rice
    leaf hoppers in paddy fields have resulted in resistant strains in
    some parts of Japan.  Several efforts have been made to solve the

    Yoshioka and others reported laboratory and field trials in which not
    only susceptible but also resistant leaf hoppers and other hoppers
    were controlled by the treatment of 30 to 40 kg/ha of combined dust

    formulations containing various compounds including small amounts of
    phenothrin (e.g. 0.8% by wt) and carbamates such as BPMC,
    O-sec-buthylphenyl-N-methyl carbamate, MTMC, m-tolyl-N-methyl
    carbamate and MPMC, 3,4-xylyl-N-methyl carbamate (e.g. 2.0% by wt).
    It is expected these formulations will be used for control of hoppers
    within the next one or two years.

    Phenothrin has advantages of a short residual life on food plants,
    quick insecticidal action and efficient control of pest strains
    resistant to organochlorine and organophosphorus insecticides.  It is
    currently being developed for controlling various pests on a range of
    fruit and vegetables.

    Post-harvest use

    Phenothrin offers advantages of improved cost/efficiency (of
    pyrethrins and bioresmethrin), reliable availability and a high degree
    of mammalian safety as a potential grain protectant.  Phenothrin
    applied at 2 mg/kg has a similar level of efficiency as commercial
    applications of bioresmethrin and pyrethrins in the control of insects
    resistant to chlorinated hydrocarbon and/or organophosphorus grain

    The pesticide is stable in grain masses, but is subject to degradation
    on exposure to ultraviolet light (Nambu et al., 1979b).

    In a series of practical commercial trials undertaken in Australia and
    involving exposures to various insects known to be resistant to other
    commonly-used pesticides, the potentialities of phenothrin for the
    protection of grains in store were well demonstrated (Desmarchelier
    et al., 1979; Bengston, et al., 1978; Working Party of Grain
    Protectants, 1979 a and b).


    Pre-harvest treatment

    Supervised trials on rice, green peppers and cabbage have been carried
    out in Japan.  Replicated results are available from each crop
    evaluated (Takimoto et al., 1977). The results are given in Table 1.

    Post-harvest treatment

    All trials on wheat, sorghum and barley grains were carried out in
    Australia except one in Japan under laboratory conditions with
    C-14-labelled (+)-trans and (+)-cis phenothrin.  Most of the
    Australian trials involved samples from commercial storages of up to
    7,435 tonnes treated with phenothrin on the proviso that the grain was
    ultimately used only as animal feed-stuff.  The temperature ranged
    from 18C to 36C and the moisture from 9.0% to 13.0%.  Applications
    were made with phenothrin or d-phenothrin mostly in combination with
    piperonyl butoxide and/or fenitrothion.  The application rates were
    mostly up to 3.0 mg/kg, but on wheat grain phenothrin was applied at

    up to 8 mg/kg.  Wheat grains were stored for up to 9 months, barley
    for up to 5 months and sorghum up to 6 months, and samples withdrawn
    for residue analysis at each indicated times.  The residues of
    phenothrin and d-phenothrin are shown in Tables 2 and 3 respectively.

    Relatively high amounts of phenothrin and d-phenothrin were detected
    after 5-9 months in those grains.  For example, in some cases more
    than half of the applied phenothrin and d-phenothrin remained in grain
    even after 9 months.  In the experiment with C-14-labelled
    (+)-trans- and (+)-cis phenothrin, only slight decomposition of
    both isomers was found months after treatment.

    Distribution of C-14-labelled (+)-trans and (+)-cis phenothrin in
    germ, endosperm and seed coat was examined after 0, 1, 3 and 6 months
    of storage at 15C and 30C (Nambu et al. 1979b).  The results are
    presented in Table 4.  Most of the applied isomers were localized at
    the seed coat and the distribution pattern did not change materially
    during 6 month storage.  Those results were evidenced by

        Table 1.  Residues of phenothrin in rice, green peppers and cabbage
              (Tests undertaken in Japan using a 25% EC formulation (Takimoto et al, 1977)

    Crop                             Interval between     Treatment
    (Rate of         Number of       applications         to sampling          Residue
    application      applications    (days)               interval             (mg/kg)
    kg ai/ha)                                             (days)

    Rice                                                                  Straw      Hulled rice
    (0.375)               6              3-10                 7           0.62          0.016
                                                             14           0.45          0.009

    Rice                                                                  Straw      Hulled rice
    (0.375)               6              6-9                  7           1.25          0.078
                                                             14           1.58          0.040

    Green pepper
    (0.50)                3              7                    1                 0.324
                                                              3                 0.660
                                                              7                 0.334
                          6              7                    1                 1.038
                                                              3                 0.625
                                                              7                 0.428
    (0.50)                3              7                    1                 0.333
                                                              3                 0.268
                                                              7                 0.469
                          6              7                    1                 0.363
                                                              3                 0.445
                                                              7                 0.244

    (0.375)               4              7                    3                 <0.005
                                                              7                 <0.005
                                                             14                 <0.005
                                                             21                 <0.005

    Table 1.  Continued...

    Crop                             Interval between     Treatment
    (Rate of         Number of       applications         to sampling          Residue
    application      applications    (days)               interval             (mg/kg)
    kg ai/ha)                                             (days)

    Cabbage               8              7                    3                  0.005
    (cont'd)                                                  7                  0.017
                                                             14                 <0.005
                                                             21                 <0.005

    (0.375)               5              7-8                 3                  <0.005
                                                             7                  <0.005
                                                             14                 <0.005
                                                             21                 <0.005
                          9              6-8                 3                   0.011
                                                             7                  <0.005
                                                             14                 <0.005
                                                             21                 <0.005

    Table 2.  Residues of phenothrin in grain after storage

              Rate of        Treatment
    Grain     application    to sampling    Residue
    (Year)    (mg ai/kg)     interval       (mg/kg)        References


    (1977)       6*          3              4.4
                             6              4.4
                             9              3.2,3.2**      Welcome
                 8*          3              6.7            Australasia,
                             6              6.9            1977
                             9              5.8, 5.2**
                 4*          3              3.0
                             6              2.7
                             9              1.6,2.8**

    (1977/78)   1.9+         0.25           1.8
                             1.5            1.42           Working Party
                             3              1.45           on Grain
                             4.5            1.71           Protectants,
                             6              1.38           1978
                             9              1.1

    (1978)      1.85+        3              1.29
                             4.5            1.3
                             6              1.1
                             7              1.21

    (1978)      2.08+        1              1.21
                2.00+        1              1.56
                2.00+        1              1.23           Working Party
                1.89+        1              1.23           on Grain
                2.1+         1              1.50           Protectants,
                2.02+        1              1.30           1979a
                2.29+        1              1.30

    (1979)      1.49+        1              1.85,1.28**
                             2              1.35
                             3              1.75
                             4              1.75
                2.01+        1              2.25,1.62**
                             2              1.8
                             3              2.05, 1.45**
                             4              1.6

    Table 2.  Continued...

              Rate of        Treatment
    Grain     application    to sampling    Residue
    (Year)    (mg ai/kg)     interval       (mg/kg)        References

    (1979)      2.01+        20 days        2.3
                             48 days        1.9
                             75 days        2.3            Working Party
                             81 days        1.6            on Grain
                1.49+        24 days        1.9            Protectants,
                             55 days        1.5            1979b
                             79 days        1.9
                             83 days        1.8


    (1978)      2.0+         1 week         1.86
                             12 weeks       2.72           Bengston
                             17 weeks       1.59           1978
                             26 weeks       1.56

    *    Nominal application
    **   Residues were determined in two different laboratories from the
         same sample
    +    Rate of application calculated from total grams phenothrin used
         divided by tons of grain treated.

    Table 3.  Residues of d-phenothrin in grain after storage


              Rate of        Treatment
    Grain     application    to sampling    Residue
    (Year)    (mg ai/kg)     interval       (mg/kg)    References


    (1978/79)    2.0+             1           1.7
                                  2           0.9
                                  3           1.1
                                  5           1.0
                                  6           0.5
                                  8           1.1

                 1.7+             1           2.4
                                  2           2.1
                                  3           1.4
                                  4           1.0
                                  5           1.1
                                  6           0.9      Desmarchelier
                                  7           0.9      et al., 1979c
                                  8           1.0
                                  9           1.0

                 1.9+             1           1.6
                                  2           0.8
                                  4           0.8
                                  5           1.0
                                  6           0.5
                                  8           0.6
                                  9           0.6

                 2.0+             1           1.5
                                  2           1.7
                                  5           1.6

                 2.0+             1           0.7
                                  3           1.0

                 1.8+             1           1.5
                                  2           1.3
                                  4           0.7
                                  6           0.7

                 1.4+             1           1.5

    Table 3.  Continued...


              Rate of        Treatment
    Grain     application    to sampling    Residue
    (Year)    (mg ai/kg)     interval       (mg/kg)    References

    (1978/79)    2.0+             1           1.3
                                  2           1.3
                                  4           1.1      Desmarchelier
                                  5           1.1      et al., 1979c
                                  6           0.9
                                  7           0.8
                                  9           0.8

                 1.9+             1           0.9
                                  2           0.7
                                  3           0.8
                                  6           0.8

                 2.1+             1           1.0
                                  3           0.7
                                  4           1.1
                                  5           0.9

                 2.0+             1           1.0
                                  3           1.0
                                  4           0.9
                                  5           1.5      Desmarchelier
                                  7           1.5      et al., 1979c

                 2.6+             2           1.3
                                  3           0.6
                                  6           1.1

                 2.2+             2           1.0
                                  3           0.8
                                  5           0.8
                                  6           1.2

                 4                1/2         3.87*,
                                              3.93**   Nambu et al,
                                  1           3.80,    1979b

                 phenothrin       3           3.78, 3.80
                                  6           3.72, 3.80

    Table 3.  Continued...


              Rate of        Treatment
    Grain     application    to sampling    Residue
    (Year)    (mg ai/kg)     interval       (mg/kg)    References

    (1978/79)    4                1/2         3.77*, 3.80**
                                  1           3.84, 3.94
                 phenothrin       3           3.87, 3.80
                                  6           3.69, 3.66

                 4                1/2         3.68*, 3.67**
                                  1           3.82, 3.78

                 phenothrin       3           3.88,
                                              3.80     Nambu et al.
                                  6           3.69,    1979b

                 4                1/2         3.85*, 3.88**
                                  1           3.80, 4.00

                 phenothrin       3           3.80, 3.93
                                  6           3.73, 3.80

                 4                1/2         3.82*, 3.99**
                                  1           4.03, 3.95
                 phenothrin       3           3.88, 4.02
                                  6           3.84, 3.55

                 4                1/2         3.90*, 4.10**
                                  1           4.03, 3.83

                 phenothrin       3           3.91, 3.89
                                  6           3.76, 3.72

    Table 3.  Continued...


              Rate of        Treatment
    Grain     application    to sampling    Residue
    (Year)    (mg ai/kg)     interval       (mg/kg)    References


    (1979/79)    2.6+             1           2.0
                                  3           1.1
                                  5           1.5
                                                       et al, 1979c
                 2.9+             2           1.5
                                  3           1.4
                                  4           1.1

    *   Grain was stored at the temperature of 15C
    **  Grain was stored at the temperature of 30C
    +   Rate of application calculated from total grams
        phenothrin used divided by tons of grain treated.

        Table 4.  Distribution of (+)-trans and (+)-cis phenothrin after storage of treated grain
              (Nambu et al., 1979b)

    Compound            Temperature    Months                      Residue (mg/kg)
                                                 Whole grain   Germ    Endosperm    Seed coat
    (+)-trans              15C          0           3.81      0.08      0.62         2.82
    (4 mg/kg)                            1           3.80      0.1       0.64         2.86
                                         3           3.78      0.09      0.63         3.09
                                         6           3.72      0.08      0.51         2.97
                           30C          1           3.90      0.12      0.77         2.95
                                         3           3.80      0.11      0.69         2.97
                                         6           3.80      0.12      0.58         3.06

    -phenothrin            15C          6           3.69      0.10      0.62         2.94
    + PBO                  30C          6           3.66      0.10      0.60         2.65
    phenothrin             15C          0           3.85      0.09      0.67         3.14
    (4 mg/kg)                            1           3.80      0.08      0.70         3.08
                                         3           3.80      0.08      0.64         3.11
                                         6           3.73      0.11      0.62         2.63
                           30C          1           4.00      0.08      0.80         3.02
                                         3           3.93      0.12      0.68         3.28
                                         6           3.80      0.14      0.58         2.75

    phenothrin             15C          6           3.76      0.12      0.58         2.92
    + PBO                  30C          6           3.72      0.10      0.59         2.79
    + Fenitrothion
    PBO: Technical piperonyl butoxide


    In animals

    (+)-trans-phenothrin labelled with C-14 in the methylene group of the
    alcohol moiety was administered orally to male Sprague-Dawley rats at
    the rate of 200 mg/kg.  The administered C-14 was almost completely
    eliminated via the urine (ca. 60%) and faeces (ca. 40%) during three
    days.  No detectable C-14-C02 was expired.  The levels of total C-14
    and phenothrin isomers in the blood, liver, kidney and brain reached
    maxima at three hours after administration and then gradually
    decreased to one-tenth to one-twentieth of the maxima in 24 hours.
    The major metabolites identified were 3-phenoxybenzoic acid (free and
    glycine conjugate), 3-(4-hydroxybenzoic) acid and 3-phenoxybenzyl
    alcohol.  A small amount of unmetabolized (+)-trans-phenothrin was
    excreted into the faeces (Miyamoto et al., 1974).

    Metabolism of (+)-cis-phenothrin in male rats was also studied.
    About 65% of the administered C-14 was recovered in faeces for three
    days post-treatment.  The faeces contained three ester metabolites
    which resulted from hydroxylation at the 4'-phenoxy position of the
    alcohol moiety, oxidation of trans-isobutenyl methyl group and
    hydroxylation of cis-geminal-dimethyl group of the acid moiety.  A
    small amount of 3-phenoxybenzoic acid was also found (Suzuki et al.,

    Thus, metabolism of phenothrin isomers proceeded rapidly in the rat
    mainly via hydrolysis of the ester linkage and oxidation at several
    positions of both alcohol and acid moieties (Fig. 1).  The metabolites
    derived from the alcohol moiety were almost completely excreted into
    the urine and faeces.

    Metabolism studies in vitro revealed that liver microsomal enzymes
    from rats, mice, guinea pigs, rabbits and dogs hydrolyse
    (+)-trans-phenothrin much faster than the cis-isomers, but the
    oxidation rate by mouse liver microsomes was somewhat faster with the
    (+)-cis isomer than with the (+)-trans isomer (Suzuki and
    Miyamoto, 1978; Soderland and Casida, 1977; Casida et al., 1979).

    FIGURE 1

    In Plants

    When (+)-trans and (+)-cis-phenothrin labelled with C-14 at the
    methylene group of the alcohol moiety were each applied to the leaf
    surface of bean and rice plants at rate of 48-50 g/20 cm2, both
    isomers rapidly disappeared from the treated leaves of both plants
    with half-lives of less than one day.  On and/or in these plants, both
    isomers underwent ozonolysis at the isobutenyl double bond to yield
    the corresponding ozonides which were rapidly decomposed to the
    corresponding aldehydes and carboxylic acids.  These ester products
    were subsequently metabolized via cleavage of the ester linkage,
    hydroxylation at 2'- and 4'- positions of the alcohol moiety, and
    oxidation of the benzyl alcohols to the benzoic acids.  The resultant
    phenols and carboxylic acids were further conjugated with sugars.  The
    parent compounds and their degradation products were hardly
    transferred from the application site to other parts of plants (Nambu
    et al., 1979a).

    Bean plant seedlings were planted in Kodaira light clay and Katano
    sandy loam soils treated with 1.0 mg/kg of C-14, phenothrin isomers.
    After 30 days, 0.01 - 0.03 mg/kg and 0.04 - 0.09 mg/kg equivalents of
    C-14 were found in pods and seeds, and shoots respectively, although
    0.21 - 3.48 mg/kg of C-14 was retained in roots.  No parent compound
    was detected in shoots (Nambu et al., 1979a).

    In soil

    (+)-trans and (+)-cis-phenothrin were applied to Kodaira light
    clay and Katano sandy loam soils at the rate of 1.0 mg/kg, and the
    treated soils were held at 25  2C in the dark.  Under upland
    conditions, both isomers were rapidly decomposed in these soils with
    half-lives of 1-2 days.  On the other hand, the rate of degradation of
    both isomers was much slower under flooded conditions, and half-lives
    were 1-2 weeks and 1-2 months for the (+)-trans and (+)-cis
    isomers, respectively.  Phenothrin isomers were decomposed in the
    soils via cleavage of the ester linkage, hydroxylation at 4'-position
    of the alcohol moiety, cleavage of the diphenyl ether linkage and
    oxidation of benzyl alcohols to benzoic acids.  These products were
    not persistent in the soils under upland conditions and the labelled
    carbon was finally decomposed to C-14-CO2 (Nambu et al., 1979b).

    Phenothrin was impregnated at a concentration of 1 g/kg on to a
    laterite from Uganda.  The treated soil was stored at 25C and 20 or
    80% relative humidity (R.H.).  The half-life of the insecticide in
    days was 40 with 20% RH and 150 with 80% RH (Barlow et al., 1977).

    (+)-trans and (+)-cis-phenothrin and their degradation products
    were hardly eluted with water from Kodaira light clay and Katano sandy
    loam soils, whereas polar products including 3-phenoxybenzoic acid
    were slightly eluted from Muko sand (Nambu et al., 1979b).

    In storage and processing

    (+)-trans- and (+)-cis-phenothrin labelled with C-14 at the
    methylene group of the alcohol moiety were applied to wheat grains at
    a concentration of 4 mg/kg alone or together with 20 mg/kg piperonyl
    butoxide and 4 mg/kg fenitrothion.  The treated grains with 11-12%
    moisture content were stored at 15 and 30C in the dark.  During 6
    months storage period, both isomers were slightly decomposed
    regardless of the presence and absence of piperonyl butoxide and
    fenitrothion.  The residue levels of phenothrin isomers were 3.64-3.78
    mg/kg in whole wheat grain, 0.79-0.83 mg/kg in flour and 9.24-11.4
    mg/kg in bran after 6 months.  The C-14 residues were mainly located
    in the seed coat as evidenced by radio-autography and radioanalysis.
    Small amounts (less than 2% of the applied C-14) of 3-phenoxybenzyl
    alcohol and 3-phenoxybenzoic acid were found.  The phenothrin residues
    in flour hardly decreased to a small extent through baking processes
    leaving 0.66-0.69 mg/kg of phenothrin isomers in bread (Nambu et al,

    All studies were carried out in Australia to determine the residues of
    phenothrin or d-phenothrin in the products after processing and
    cooking of wheat, oats, barley and rice grain, except one experiment
    with wheat grain in Japan using labelled compounds.

    Wheat grain containing 0.5-3.9 mg/kg of phenothrin was used for the
    studies, and the residue results after processing and cooking are
    summarised in Table 5.  Although higher residues were found in bran
    and pollard after processing, the residues in flour were reduced and
    reached 10.6-25.0% of those found in whole grain.  After cooking the
    residues in bread did not exceed 0.2 mg/kg in Australian trials, but
    in the Japanese trial those residues of C-14-labelled (+)-trans and
    (+)-cis phenothrin were relatively high (0.69 mg/kg and 0.66 mg/kg)
    corresponding to the higher residues in flour (0.79 mg/kg and 0.91
    mg/kg).  This is supposed to be caused by contamination of a large
    portion of testa in flour from the crease area of grain, while in
    normal commercial flour milling situations only a very small portion
    of testa would go into flour.  In gluten, the residue was higher (1.9
    mg/kg) than that in flour (0.3 mg/kg).  However, the pesticide
    residues in gluten does not cause concern, because normally there
    would be a 2% maximum addition of gluten in bread.

    Oats containing 1.2 mg/kg of phenothrin were processed and cooked
    (Desmarchelier, 1979a).  Most of the residues were carried in oat
    hulls, and low residue levels were found in both groats (0.3 mg/kg)
    and rolled oats (0.1 mg/kg).  In porridge the residue was below the
    detection limit of 0.05 mg/kg.

    Barley containing 3.2 mg/kg and 0.92 mg/kg phenothrin was processed
    into malt, wort and cattle feed.  Of these products, the highest
    residues were found in the malt, but these levels, 0.63 mg/kg and 0.15
    mg/kg were less than one-fifth of that in barley.  In wort, the
    residues were less than the detection limit of 0.02 mg/kg.

        Table 5.  Residues of phenothrin and d-phenothrin prior to and after processing and cooking of wheat

                                                            Residue (mg/kg)
    Compound                                                                                                 Reference
                                                                  Wholemeal   White
                             Wheat    Bran     Pollard   Flour    Bread       Bread      Gluten    Starch

    Phenothrin                1.2     5.6        3.6     0.21      0.74       0.16       -         -         Bengston 1979
                              3.0     10.0       4.1     0.82      -          0.18       -         -         Desmarchelier, 1979a
                              1.5     6.0        3.0     0.4       -          0.1        -         -                "
                              0.9     3.0        2.0     0.15      -          0.05       -         -                "
                              0.5     1.6        0.9     0.09      -          <0.05      -         -                "
                              3.9     8.1        1.6     0.65      -          -          1.9       <0.05            "
                              1.2     4.0        1.8     0.3       0.4-0.6    0.1-0.2    -         -         Ardley, 1979
                              2.0     -          -       -         -          <0.1       -         -         Mollard, 1979
                              4.3     -          -       -         -          <0.1       -         -                "

    (+)-trans-phenothrin      3.78    11.4       -       0.79      -          0.69       -         -         Nambu et al
    (+)-cis-phenothrin        3.64    9.24       -       0.91      -          0.66       -         -

    A nominal application of 8 mg/kg phenothrin was applied to husked
    (brown) rice and polished (white) rice.  Six months after application,
    husked (6.2 mg/kg of phenothrin) and polished (5.9 mg/kg) rice were
    cooked in a minimum amount of boiling water for 25 minutes.  Unhusked
    rice was also treated with d-phenothrin at a rate of 8 mg/kg, and
    after 6 months of storage when 4.7 mg/kg of phenothrin was detected,
    rice was milled into husked and polished rice, and cooked as described
    above.  As shown in Table 6, the cooking of rice had the effect of
    reducing residues by from 34% to 60%.  It also has indicated that the
    milling of rice from husked (paddy) to unhusked (brown) or polished
    (white) is a major means of residue reduction, that is, 90% and 97%

    Table 6.  Residues of d-phenothrin prior to and following processing
              and cooking of rice

                        Residue (mg/kg)
    Unhusked       Husked         Polished       Cooked

       -            6.2              -            4.1
       -             -              5.9           3.1
      4.7           0.50             -            0.2
      4.7            -              0.15         <0.1

    (Desmarchelier et al., 1979d)

    Phenothrin and d-phenothrin were applied to grain at the level of 4
    mg/kg and 2 mg/kg, respectively, and have encountered levels of
    moisture and three temperature levels.  As shown in Fig. 2 and 3, both
    increasing temperature (25, 30 and 37C) at a constant moisture of
    11.8% and increasing moisture (9.3, 11.8 and 13.4%) at a constant
    temperature of 30C led to increased breakdown of phenothrin and
    d-phenothrin (Maguire, 1977).

    Photochemical Degradation

    When exposed to daylight in England near a window and out of doors
    under quartz plates, phenothrin decomposed rapidly with half-lives of
    4 and 7 days.  Under these conditions phenothrin was more unstable
    than permethrin and more stable than bioresmethrin (Elliot et al.,
    1973).  In a separate study, decomposition of phenothrin on glass by
    irradiation of 270-370 mm light was determined.  The half-life for
    phenothrin was one day (Barlow et al., 1977).


    Due to the newness of phenothrin and its largely experimental status,
    no information was available on residues in food in commerce or at

    FIGURE 2

    FIGURE 3


    Residue determination of intact phenothrin by gas-liquid
    chromatography (GLC) is difficult due to poor sensitivity to the GLC
    detectors commonly used in residue analysis, though some residue data
    of d-phenothrin on stored sorghum (0.4 - 0.95 mg/kg) were obtained by
    GLC equipped with flame ionization detector (Bengston et al., 1977).
    Kato et al. (1979) successfully applied combined gas-liquid
    chromatograph/Mass spectrometry (GLC/MS) to determine intact
    d-phenothrin residues in blood.  Mass fragmentography of d-phenothrin
    gave as minimum detectable amounts 0.1 ng and 0.04 ng at mass ions,
    m/e 350 (parent) and 183, respectively, thereby allowing confirmation
    as well as quantitation of 0.005 mg/kg or even less.  Desmarchelier
    (1979a) also briefly reported utility of GLC/MS for analysis of
    phenothrin in stored grains at residue levels below 0.01 mg/kg without
    presenting detailed data.

    As a determinative procedure Simpson (1979) adopted high pressure
    liquid chromatography in combination with cleanup by partitioning
    between n-hexane and acetonitrile, and alumina column chromatography.
    By this method phenothrin residues of 1.56-2.72 mg/kg were quantitated
    in stored sorghum, though data on detection limits and recoveries are
    not presented (Bengston et al., 1978; Simpson 1979).

    Derivatization methods have been more commonly adopted for residue
    analysis.  Takimoto et al., (1977) analyzed phenothrin residues by
    the procedures which included potassium hydroxide-catalyzed hydrolysis
    of phenothrin in aqueous methanol and subsequent pyridine-catalyzed
    esterification of the liberated alcohol moiety with
    2,4-dichlorobenzoyl chloride.  When analyzed by GLC fitted with 0.8
    m-long glass column packed either with 4% FFAP on Gas-chrom Q or with
    3% OV-101/3% Apiezon Grease L on Gas-chrom Q, 3-phenoxy-benzyl
    2,4-dichlorobenzoate showed excellent sensitivity, i.e. 0.04-0.1 ng as
    minimum detectability, to electron-capture detector, which permitted
    detection of phenothrin at 0.005-0.02 mg/kg.

    Desmarchelier (1976; 1979a) extended the colorimetric procedures which
    had originally been devised by McClellan (1964) for residue analysis
    of pyrethrum.  The procedures were based upon a color reaction of a
    modified Deniges reagent with chrysanthemic acid formed by hydrolysis
    of phenothrin under catalysis of sodium hydroxide in aqueous alcoholic
    solution.  The method appears less laborious but less selective and
    less sensitive than that reported by Takimoto et al., (1977).  In
    addition, a significant difference in extinction coefficient observed
    at 584 nm between (+)-cis and (+)-trans chrysanthemic acid
    necessitates prior separation of cis and trans isomers for
    accurate determination of phenothrin.

    Thin-layer chromatography (TLC) based on the above colour reaction has
    also been applied as a semiquantitative procedure (Desmarchelier 1976,

    The solvent or solvent combinations selected for extraction of
    phenothrin depend upon the nature of substrates.  From the substrated
    with high-moisture contents like cabbage and green pepper, phenothrin
    was effectively extracted by chopping and blending either with polar
    solvents, e.g., methanolacetonitrile, or with nonpolar-polar solvent
    mixtures, e.g., benzene-ethanol (Takimoto et al., 1977).  For aged
    phenothrin residues on cooked rice 24-hour extraction with polar
    solvents, e.g. methanol and ethanol, gave complete recoveries whereas
    the extraction with non-polar solvents, e.g. light petroleum and
    hexane, resulted in poor recoveries (Desmarchelier 1979b).  From dry
    and low-moisture substrates including rice, barley, wheat, oats and
    sorghum phenothrin is efficiently extracted with either polar,
    non-polar or dual solvent system.  Hulled rice grain was ground and
    macerated overnight in methanol (Takimoto et al., 1977).  Wheat and
    barley were soaked overnight as whole grain either in light petroleum
    in ethanol (Desmarchelier 1979b).  Desmarchelier (1976) reported that
    use of light petroleum simplified cleanup in the analysis of grains.

    As cleanup procedures both liquid chromatography (LC; Florisil and
    alumina) and TLC (silica-gel) are used for intact phenothrin residues
    (Takimoto et al., 1977; Simpson 1979).  The Florisil column
    chromatography coupled with benzene-ethyl acetate extraction resulted
    in 93% recovery, as determined by GLC/MS, from the blood fortified at
    0.05 mg/kg (Kato et al., 1979).  Cleanup procedures employed for the
    derivatization methods obviously reflect the nature of the derivatives
    as well as substrates.  The method of converting phenothrin to
    3-phenoxybenzyl 2,4,dichlorobenzoate which provided 81-88% recoveries
    for cabbage, green pepper and hulled rice fortified at 0.1-1 mg/kg
    included cleanup by either LC or TLC before both hydrolysis and GLC
    quantitation (Takimoto et al., 1977).  The colorimetric method
    employed partition cleanup between aqueous phases and nonpolar
    solvents, e.g. light petroleum or chloroform, and satisfactory
    recoveries of 87-91% were achieved from cooked rice (Desmarchelier,


    No information was available.


    Phenothrin is more stable than natural pyrethrins and synthetic
    pyrethroids developed earlier, but it is relatively degradable by
    sunlight.  The principal current uses are (1) in household aerosols
    and sprays formulated in combination with tetramethrin, piperonyl
    butoxide, carbamates and/or fenitrothion for control of various
    species of plant hoppers and for control of houseflies, mosquitoes,
    cockroaches and other household or public health pests, and (2) in
    grain protection.  Supervised trials have been undertaken on rice,
    green peppers and cabbage.

    The most important food use at present is for the protection of stored
    grains.  Extensive trials on wheat, sorghum and barley grains were
    carried out in Australia and Japan.  Wheat was stored up to 9 months,
    barley up to 5 months, and sorghum up to 6 months and samples were
    withdrawn for residue analysis at a variety of intervals.  Treatment
    levels of approximately 2 mg a.i./kg usually gave residues of about 2
    mg/kg at 1 month after treatment, falling to about 1 mg/kg after 9
    months.  Similar results were obtained for sorghum and barley.
    Increasing temperature and moisture resulted in increased breakdown of
    phenothrin, but the effect was not large.  Wheat residues were found
    mostly in the seed coat.

    Processing of wheat, oats, barley and rice resulted in somewhat higher
    residues in wheat bran, wheat pollard, and oat hulls and lower
    residues in wheat flour, groats, rolled oats, barley malt, wort,
    barley cattle feed and polished rice.  Cooking resulted in reduced
    residues in bread, porridge and boiled rice.

    In studies with 14C-labelled (+)-trans and (+)-cis- phenothrin
    applied to bean and rice plant leaf surfaces, both isomers disappeared
    rapidly with half-lives of less than one day.  Both isomers underwent
    ozonolysis and sequential metabolism to give final products consisting
    of sugar conjugates of phenols and carboxylic acids.  No translocation
    of parent compounds and their degradation products from the
    application site occurred.  Bean seedlings planted in 14C-phenothrin
    treated soil did not show translocation of parent compound into the

    Stored wheat (11-12% moisture) treated with 14C-phenothrin isomers at
    4 mg/kg either alone or in combination with piperonyl butoxide and
    fenitrothion was held at either 15 or 30C in the dark for six months.
    During this interval only slight degradation occurred with 3.6-3.8
    mg/kg remaining in whole wheat grain, mainly in the seed coat.  Small
    amounts ('2% of applied 14C) of 3-phenoxybenzyl alcohol and
    3-phenoxybenzoic acid were found.

    When exposed to daylight in England near a window and out of doors
    under quartz plates, phenothrin decomposed rapidly with half-lives of
    4 to 7 days.  Photostability of phenothrin was greater than
    bioresmethrin and less than permethrin.  Phenothrin films on glass
    irradiated by 270-370 nm light had a half-life of one day.

    Residue determination of intact phenothrin by GLC is complicated by
    its molecular structure which results in poor sensitivity in selective
    detectors such as the electron capture, necessitating the use of the
    non-selective flame ionization detector with its attendant rigorous
    cleanup requirements.  Combined GC-Mass spectrometry has been
    successfully used to determine d-phenothrin in blood at levels as low
    as 0.04 ng, allowing quantitation at 0.005 mg/kg.  GC-MS has also been
    used for residues in stored grains, but such techniques will probably
    not find wide acceptance for some time.  The colorimetric procedure
    for pyrethrum has been extended to phenothrin, but since the method is

    based on a colour reaction involving chrysanthemic acid, it would not
    distinguish between most synthetic and natural pyrethroids.  High
    performance liquid chromatography with UV absorption detection has
    also been used to determine residues in stored sorghum.  Rapid
    improvements in LC column technology combined with variable  
    wavelength UV detectors should result in methods of greater
    selectivity and sensitivity and merits further development.  Although
    tedious, the derivatization method developed by Takimoto, et al.
    appears to be the most suitable for regulatory analysis.  The method
    gives overall recoveries of 81-88%.


    Because phenothrin was not evaluated for an ADI in 1979, only
    guideline levels can be presented at this time.

    The following residue levels for phenothrin as combined (+)-trans
    and (+) cis-isomers are those which need not be exceeded if the
    compound is used as recommended for the protection of stored grains.

                 Commodity               Guideline level
                 Wheat bran                     15
                 Cereal grains                   5



    1.  Further residue data from supervised trials on commodities for
        which phenothrin uses are developed, especially stored products,
        vegetables, rice and cereal brans and straws used as animal feed.

    2.  Continued development of improved methods of residue analysis for
        the intact isomer molecules.


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    See Also:
       Toxicological Abbreviations
       Phenothrin (Pesticide residues in food: 1980 evaluations)
       Phenothrin (Pesticide residues in food: 1984 evaluations)