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    FENTHION      JMPR 1977

    Explanation

    Fenthion was evaluated in 1971 (FAO/WHO 1972) and in 1975 (FA0/WHO
    1976) and a temporary acceptable daily intake was estimated to be
    0.0005 mg/kg bw. Temporary maximum residue limits were recommended for
    a range of fruits, vegetables, grain and foods of animal origin. It
    was indicated that certain specific toxicological information was
    required before the acceptable daily intake and maximum residue limits
    could be confirmed. Residue data from supervised trials on other
    citrus fruits (especially lemons), coffee, cucurbits, onions and
    potatoes and additional residue data on sugar beet roots and tops were
    also required.

    In 1977 the 9th Session of the Codex Committee on Pesticide Residues
    requested the Joint Meeting to review maximum residue limits in the
    light of information provided by governments and other relevant
    information such as disappearance rate.

    The results of a considerable number of supervised residue studies
    were provided by the principal manufacturer (Bayer, 1977). Information
    was also received from Poland, the Philipines, Turkey, the USA and
    from the scientific literature in part fulfillment of the above
    requirements, and the following monograph addendum reflects the
    evaluation of this information. No new toxicological data were made
    available in sufficient time for consideration.

    RESIDUES IN FOOD AND OTHER EVALUATION

    RESIDUES RESULTING FROM SUPERVISED TRIALS

    The results of studies carried out on alfalfa, apples, bananas, beans,
    cherries, grapes, grass, olives, onions, oranges, peaches, pears,
    plums, potatoes, sweet potatoes, rice., strawberries and tomatoes are
    summarized in Table 1.

    These data represent the results of a large number of separate trials
    (average of 3 for each pre-harvest interval). The results indicate
    that the recommended maximum residue limits for fenthion residues in
    apples, cherries, grapes, olives, peaches and rice are appropriate,
    being neither too high nor too low to accommodate the maximum values
    reported.

    Bananas

    The use of fenthion as a post-harvest dip to control fruit flies in
    bananas and other tropical fruits is important in order to be able to
    comply with the phytosanitary requirements of many importing
    countries. The studies in the Philippines (Magallona, 1977) indicate
    that such treatment results in the bulk of the residue being retained
    in the peel (1-2 mg/kg) with 0.3-0.5 mg/kg occurring in the pulp
    (peeled fruit).

    Citrus

    In the case of oranges it is obvious that residues in excess of the
    recommended maximum residue level can occur even 50-60 days after the
    application of normal rates of fenthion. Table 1 gives details of
    studies made in Japan in 1972. (Bayer, 1977) which indicate that the
    following the spraying of orange trees with fenthion at the rate of
    2.7 - 3kg/ha, the residue in the whole fruit is of the order of 1
    mg/kg when harvested 50/60 days later. Of this residue about 0.05-0.15
    mg/kg is in the juice and 1.0-5.8 mg/kg in the peel. Reference to the
    1971 monograph (FAO/WHO 1972) reveals that the previous recommendation
    is based on studies where fenthion was applied at the much lower rate
    of 300 g/ha.

    Studies made in Turkey in 1967-1969 (Kirca, 1976) on oranges and
    tangerines show that the application of fenthion/sugar bait to
    tangerines for the control of fruit fly produces residues in the whole
    fruit ranging from 0.25-4 mg/kg 7-10 days after the last application
    and up to 2 mg/kg 21 days after treatment. (See Table 1.) Because the
    maximum residue limit recommended by the Joint Meeting did not
    accommodate these residues, the use of fenthion was not accepted in
    Turkey for the control of fruit fly. Fenthion is widely used on citrus
    against fruit fly and consideration must be given to the establishment
    of a maximum residue limit appropriate for these needs.

    Olives

    Extensive studies in Turkey between 1963 and 1975 (Kirca, 1976) show
    that olives treated for the control of live fruit fly and
    Mediterranean fruit fly take up considerable amounts of fenthion which
    dissipate slowly. Only by careful control of the application rate and
    by strict observance of a 30-day pre-harvest interval is it possible
    to comply with the currently recommended limit of 2 mg/kg in harvested
    olives.

    Pears and plums

    Residue studies on pears (Bayer, 1977) and on plums (Glogowski et al.,
    1974) provide a basis for proposing maximum residue limits on these
    fruits (See Table 1.)

    Potatoes

    Data were available from Japan (Bayer, 1977) from 5 trials in
    different regions of the country where fenthion spray applied three
    times at a concentration of 0.05% and at the rate of 1200-20001ha
    with the last spray 15 days and 30 days prior to the harvest. None of
    the tubers harvested were found to contain residues when examined by
    methods sensitive to 0.001 mg/kg.

    In the light of the data summarized in Table 1, it is possible to
    propose revised or additional maximum residue limits for fenthion in
    bananas, beans, citrus, onions, pears, plums, potatoes, sweet


        TABLE 1. Residues of penthion resulting from supervised trials
                                                                                                                                           
                                                Application                            Residues (mg/kg) at intervals (days) after application
                                                  rate
    Crop          Country      Year   no   kg ai./ha   formulation     0/1        3         7         14          21       28        35 
                                                                                                                                           

    Alfalfa       Turkey       1970   1    0.75        Dust                      0.1      0.25
                  U.S.A.       1976   1    0.11        SC             3.58                0.65
    Apples        Germany      1971   1    0-7-1.4g/   EC           0.75-0.9             0.5-0.7   0.15-0.25   0.15-0.2           0.05-0.1
                                           tree
    (Renette)     Poland       1969   1    0.5         EC             5.32      1.94       1.2       0.11        0.08     0.03      Trace
    (Starking)    Poland       1969   1    0.5         EC              8.2      3.07      1.06       0.11        0.06     0.03      Trace
    (Jonathan)    Poland       1970   1    1.1-1.25    EC             10.06     4.12      2.73       1.55        0.40     0.20      0.16
    (Starking)    Poland       1970   1    1-1-1.25    EC             15.11     2.65      1.66       0.41        0.35     trace     --- 

    Bananas       Phillipines  1977   1    0.04%       EC                        1.2
    (peel)        Phillipines         1    0.05%       EC                        1.2
    post-harvest  Phillipines         1    0.075%      EC                        1.3
    (pulp)        Phillipines         1    0.04%       EC                        0.3
    post-harvest  Phillipines         1    0.05%       EC                        0.5
                  Phillipines         1    0.075%      EC                        0.9

    Beans         Japan        1972   5    0.5         EC                                                         nd       nd        nd

    Cherries      Germany      1971   1    1.4g/tree   EC            0.8-0.9  0.55-0.7  0.3-0.45   0.05-0.1
                                      1    1.4g/tree   EC            0.7-6.7   0.4-0.8  0.1-1.95    nd -0.3
                  Poland       1970   1    11.3g/tree  EC             19.15     6.14      3.58       1.32        0.35     0.24      trace
                               1971   1    11.3g/tree  EC             19.0      12.54     6.45       2.03        0.70
    Grapes        Japan        1972   2    0.07-1.5    EC                                1-1.24    0.35-0.4     nd-0.29    nd        nd

    Grass         U.S.A.       1976   10   0.11        SC           1.12-1.86
                  Turkey       1974   1    4           oil                                            46          5.9

    Olives        Turkey       1963   1    0.075       EC                                  5.1                    3.1                 0.97
                               1964   1    6:75g/tree  EC                                             2.7         2.0      3.1
                               1975   1    7.5g/tree   EC                                  6.5                    1.7                 trace
                  Turkey       1965   1    14 g/tree   EC                                 4.04       1.94        0.56                 0.4
                               1965   2    0.075%      EC                                  6.5                    3.2                 1.0


    TABLE 1. (Continued)

                                                                                                                                           

                                                Application                            Residues (mg/kg) at intervals (days) after application
                                                  rate
    Crop          Country      Year   no   kg ai./ha   formulation     0/1        3         7         14          21       28        35 
                                                                                                                                           

    Onions        Japan        1970   1    0.5-1.0     EC                      nd-0.08   nd-0.06                nd-0.03

    Oranges
    (flesh)       Japan        1972   2    2-7-3.0     EC                                                                             nd-0.02
    (peel)                            2    2.7-3.0     EC                                                                             1.0-5.8
    (juice)                           2    2.7-3.0     EC                                                                             0.06-0.14

    Oranges       Turkey       1969   3    1%          bait                               0.87                   0.57
                               1969   6    1%          bait           1.73
    Peaches       Japan        1969   6    0.35-1.6    WP                     0.03-1.2  0.03-1.0   0.06-0.5

    Pears         Japan        1969   5    1.0 -2.8    WP                               0.004-1.4               nd-0.9  0.15-0.18

    Plums         Poland       1969   1    0.075%      EC             7.11      2.82      0.85        0.2        0.11                 0.06
                               1970   1    0.075%      EC             10.85     9.45      3.72        0.8         0.6      0.5        trace

    Potatoes      Japan        1970   3    0.5-1.0     EC;                                            nd          nd       nd


    Sweet
    Potatoes      Japan        1973   1    3.0-4.5     Gran                                                                           nd-0.01

    Rice in husk  U.S.A.       1972   3    0.11        Gran                                                    0.01-0.02

    Rice hulled   Japan        1973   4    0.5-0.75    EC                                         0.022-0.035   nd-0.07  nd-0.06      nd-0.008
    Rice hulled   Japan        1972   3    2           Gran                                           nd                   nd        nd
    Rice huIled   Japan        1969   3    0.6-0.9     SC                                 0.016       nd                   nd        nd
    Rice
    polished      Japan        1969   1    0.5 -0.75   EC                                             nd          nd

    Strawberries  Japan        1971   2    0.6 -1.5    EC           1.0-2.87  0.67-1.6  0.16-1.7   0.03-0.9

    TABLE 1. (Continued)

                                                                                                                                           

                                                Application                            Residues (mg/kg) at intervals (days) after application
                                                  rate
    Crop          Country      Year   no   kg ai./ha   formulation     0/1        3         7         14          21       28        35 
                                                                                                                                           

    Tangerines    Turkey       1967   1    1%          bait                                0.8                   0.12
                                      2    1%          bait                               0.25
                                      4    1%          bait                               4.00                   1.10
                               1968   1    1%          bait                               0.71                   0.53
                               1969   3    1%          bait                               2.92                   2.00
                               1969   6    1%          bait           3.19
    Tomatoes      Japan        1970   2    0.9 -1.5    EC            nd-0.89   nd-0.34   nd-0.06                  nd
                                                                                                                                           
    

    potatoes, strawberries and tomatoes. See also "Fate of residues",
    "In plants".

    FATE OF RESIDUES

    In animals

    Avrahami and White (1975) treated two lactating dairy cows with 20%
    fenthion as a topical spot-treatment used for the control of lice
    using 32P-labelled fenthion applied at the rate of 9 mg/kg body
    weight. Highest residues of total radioactivity in the blood, milk
    urine and faeces appeared between the first and second day after
    treatment. The residues were predominantly water-soluble hydrolysis
    products of fenthion. The highest daily average level of fenthion and
    its organosoluble metabolites in the milk from the two cows was
    approximately 0.1 mg/kg on the first day after treatment. Of the total
    radioactivity applied to each cow, 45-55% was recovered in the urine,
    2-2.5% in the faeces and 1.5-2% in the milk over a period of 4 weeks.

    Johnson and Bowman (1972) administered fenthion to lactating dairy
    cows at the rate of 25, 50 and 100 ppm in the total daily ration for
    28 days. Total residues consisting of fenthion, its sulphoxide and
    sulphone and the sulphoxide and sulphone of the oxygen analogue in the
    milk averaged 0.016, 0.049 and 0.099 mg/kg, respectively over the
    period. Total residues in faeces consisted of fenthion and its
    sulphoxide and averaged from 0.042 to 0.308 mg/kg. Neither fenthion
    nor its oxygen analogue was found in urine but totals of the
    sulphoxide and sulphone of fenthion and its oxygen analogue averaged
    from 0.43 to 1.05 mg/kg. Seven days after feeding was terminated,
    residues could not be detected in milk, urine or faeces.

    In plants

    Zadrozinska (IT2) studied the metabolism of fenthion in broadbean
    plants and blackcurrants following topical application, by taking
    samples every second day until biological activity could no longer be
    traced. Fenthion disappeared quickly and four metabolites were
    identified as fenthion sulphoxide, fenthion sulphone, fenoxon
    sulphoxide and fenoxon sulphone. Fenthion sulphoxide was the most
    durable compound, still being found 30 days after application to beans
    and 64 days after treating currants.

    Glogowski et al. (1974) studied the rate of degradation of fenthion
    residues in apples, plums and sweet cherries over two cropping seasons
    in Poland. Residues of fenthion and its metabolites in apples averaged
    5.1-5.3 mg/kg immediately after treatment, 0.1-1.5 mg/kg after 14 days
    and always less than 1 mg/kg at 21 days. By the 35th day, the residues
    were below the limit of determination (0.05 mg/kg). During the 35-day
    post-treatment period the average weight of each apple had increased
    from 3 to 44 g. Part of the reduction is thus due to growth dilution.

    In the case of sweet cherries, the same workers showed that the
    initial deposit of about 20 mg/kg had declined to about 0.5 mg/kg by
    the 21st day after spraying. The fruit in this time had increased in
    weight from about 1 g. to 6 g. The similar pattern was observed in
    plums where the concentration of residues declined from 10 mg/kg to

    0.05 mg/kg in 28 days. In all these trials the treatment had been
    applied at the optimum time for the control of the major pest species.

    These studies indicate there is considerable similarity in the rate of
    decline of fenthion residues on the different fruits, apples, cherries
    and plums. Table 2, sets out the data from the work of Glogowski et
    al. (1974) in a manner that permits ready comparison between the
    residue levels on different species of fruit, and different cultivars,
    in succeeding years. It is obvious that the effect of season and
    cultivar is at least as great as the influence of fruit variety. This
    study provides valuable insight into the variability of residue levels
    notwithstanding efforts to standardize conditions and test procedures.
    It provides a warning of the danger of establishing maximum residue
    limits on the basis of limited trials data.

    In applying these findings it should be recognized that the residues
    resulting from a treatment 21 days before harvest, for example, would
    not necessarily be the same as that found 21 days after a spraying
    applied at a stage when the fruit would not normally be picked for
    about 35 days (i.e. to very much more immature fruit).

    In processing and cooking

    Trials made in Turkey in 1968 and 1969 involved the treatment of tea
    bushes with fenthion sprays and the subsequent harvesting of leaves
    for the manufacture of (fermented) tea. The application of fenthion
    sprays containing 50g. fenthion per 100 l of spray produced a residue
    in manufactured tea ranging from 0.48 to 1.60 mg/kg when the leaves
    were picked 17 days after the second of two sprays: when the spray
    concentration was increased to 63g/100 l and the leaves harvested 24
    days after a single spray the residues in the manufactured tea reached
    1.38 mg/kg. Fenthion has not yet been adopted for use on tea crops in
    Turkey.

    In soil

    The paper of Walnofer et al. (1976) demonstrates that the soil fungus
    Rhizopus japonicus in nutrient solution is capable of oxidizing
    fenthion to yield the sulphoxides of both fenthion and its oxygen
    analogue. The only product of enzymic hydrolysis was the "phenol
    sulphoxide" (3-methyl-4-methylsulphinylphenol).

    In water

    Fredrickson and Nichols (1976) studied the photodecomposition of
    fenthion in aqueous solution of concentration 5 mg/l at 5C and 25C
    using artificial illumination closely approximating sunlight. They
    showed that fenthion decomposed with a half-life of 55 minutes at 5C,
    15 minutes at 25C and 10 minutes when sensitized with 2% acetone.


        TABLE 2 Disappearance of fenthion residues from apples, plums, cherries (Glogowski et al., 1974)

                                                                                                      

                             Residue, mg/kg, in (fruit, cultivar and year)
    Days after      Apples   Apples    Apples    Apples    Plums     Plums     Cherries  Cherries
    spraying        A        B         C         B         D         E         G         G
                    1969     1969      1970      1970      1969      1970      1970      1971
                                                                                                      
    0               5.32     8.20      10.06     15.11     7.11      10.85     19.15     19.00
    1                                  8.05      2.92
    3               1.94     3.07      4.12      2.65      2.82      9.45      6.14      12.54
    7               1.20     1.06      2.73      1.66      0.85      3.72      3.58      6.45
    10              0.42     0.38      1.82      1.19      -         0.91      2.78      2.37
    14              0.11     0.11      1.55      0.41      0.20      0.80      1.32      2.03
    21              0.08     0.06      0.40      0.35      0.11      0.60      0.35      0.70
    28              0.03     0.03      0.20      TRACE     0.06      0.05      0.24      -
    35              TRACE    TRACE     0.16      -         -         TRACE     TRACE     -
                                                                                                      

    

    Degradation products were the sulphoxide, sulphone, oxygen analogue
    and its sulphoxide together with the corresponding phenol, phenol
    sulphoxide and phenol sulphone. Up to 39% of the radioactivity
    represented polar degradation products believed to be polymeric.

    EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION

    Information supplied by the US Food and Drug Administration indicated
    that in the course of monitoring residues in domestic food commodities
    during 1975 and 1976, fenthion residues were found in peaches (0.02
    mg/kg), paprika (0.04 mg/kg), peppers (0.022 mg/kg) and potatoes
    (trace). No other information came to hand.

    APPRAISAL

    Following evaluation by the Joint Meeting in 1971 a request was made
    for additional information on the occurrence of residues in citrus
    fruit, coffee, cucurbits, onions, potatoes, sugar beet roots and tops.
    The 9th (1977) Session of the Codex Committee on Pesticide Residues
    requested a review of the maximum residue limits in the light of
    information provided by governments and other relevant data such as
    disappearance.

    Results from a considerable number of supervised residue studies were
    provided by the principal manufacturer and by Poland, the Phillipines
    and Turkey. Other information was provided by the USA and by published
    scientific literature.

    This information has confirmed that the maximum residue limits
    previously recommended for fenthion residues in apples, cherries,
    grapes, peaches and rice are adequate to cover the residues resulting
    from approved uses of fenthion provided there is a reasonable pre-
    harvest interval. None of the maximum residue limits appear
    excessively high in the light of the new data.

    One extensive study from Poland carried out over two seasons
    demonstrates the rate of decline of fenthion in apples, cherries and
    plums. There is considerable similarity between the rates of decline
    of residues on the different species of fruit that is partly
    influenced by growth dilution. Fourteen or 21 days after spraying, the
    difference in residue level between two distinctly different fruits is
    often less than the difference between two cultivars of the same
    species or between residue levels in the same cultivars in two
    succeeding years. This study is a very useful indicator of the
    variability of residue levels notwithstanding efforts to standardize
    conditions and test procedures. It points to the danger in placing too
    much reliance on limited amounts of data as representing the position
    in different regions, seasons, cultivars, formulations and application
    techniques.

    Residue data from studies in Turkey and Japan point to the need to
    raise the maximum residue limit for fenthion in citrus fruit where
    residues occur mainly in the peel. Studies in Japan show that the use
    of fenthion on potato plants does not give rise to measurable residues
    in potato tubers.

    Information considered by the meeting provides a basis for
    recommending additional maximum residue limits in bananas, beans,
    onions, pears, plums, potatoes, strawberries, sweet potatoes and
    tomatoes.

    Extensive studies in Turkey indicate that there is a high risk that
    olives treated for the control of fruit flies will contain residues
    above the maximum residue limit even when a 30-day pre-harvest
    interval is observed.

    Further studies have confirmed that fenthion present in livestock feed
    or used for the control of external parasites gives rise to low but
    transitory residues in milk. The metabolism of fenthion in cattle has
    been clarified by these studies.

    It has been shown that sunlight causes rapid degradation of fenthion
    and the production of polar products believed to be polymeric phenols.

    No information was received to assist in resolving the questions about
    residues in coffee, cucurbits and sugar beets.

    RECOMMENDATIONS

    The temporary maximum residue limits previously recommended, with the
    exception of the limit for oranges which is replaced by a higher limit
    for citrus, are confirmed. New recommendations are listed below.

    They refer to the sum of fenthion, fenthion sulphoxide, fenthion
    sulphone and the oxygen analogues of these compounds, determined as
    the sulphone of the oxygen analogue and expressed as fenthion.

    FURTHER WORK OR INFORMATION

    REQUIRED (by July, 1978)

    1. Adequate two-year feeding studies in the dog in one rodent species.

    2. Establishment of the sequence of metabolic changes in humans and
    laboratory animals in order to elucidate the mechanism of
    cholinesterase inhibition.

        TABLE

                                                                                  

    Commodity                     Limits, mg/kg       Pre-harvest interval on
                                                      which recommendations
                                                      are based
                                                                                  

    Bananas                       1                   post-harvest
    Beans                         0.1                 21
    Citrus                        2                   21
    Citrus juice                  0.2                 21
    Onions                        0.1                 14
    Pears                         2                   10
    Plums                         1                   21
    Potatoes                      0.05*               28
    Sweet Potatoes                0.1                 28
    Strawberries                  2                   7
    Tomatoes                      0.5                 7

                                                                                  

    * at or about limit of determination

    
    DESIRABLE

    1. Information from additional countries on crops already considered
    and on additional crops in order to confirm the level of residues
    following approved uses of fenthion.

    2. Information on the effect of processing and cooking on fenthion
    residues in fruits and vegetables.

    REFERENCES

    Avrahami, M., and White, D.A. (1975) Residues in milk of cows after
    spot-treatment with 32P-fenthion. New Zealand J. Exptl. Agric. 3,
    309-311.

    Bayer, A.G. (1977) Residues of Fenthion in Crops - Biologische
    Forschsung Submission to FAO, Nov. 1977.

    FAO/WHO, (1972) 1971 Evaluations of some pesticide residues in food
    - WHO Pesticide Residue Series No. 1; FAO Document AGP -1971/M/9/1.

    FAO/WHO, (1976) 1975 Evaluations of some pesticide residues in food
    - WHO Pesticide Residues in food - WHO Pesticide Residue Series No. 51
    FAO Document AGP 1971/M/13.

    Fredrickson, D.R. and Nichols, S.S. (1976) Photodecomposition of
    BAYTEX - Chemagro Division, Mobay Chemical Corporation Report No.
    49347, Aug. 9, 1976.

    Glogowski, K., Welter, M., Czaplicki, E. and Witkowskiy W. (1974)
    Studies on the degradation rate of fenthion residues in apples, plums
    and sweet cherries sprayed with LEBAYCID - Pflanzenschutz-Nachrichten
    Bayer 27(2) 156-166.

    Johnson, J.C. and Bowman, M.C. (1972) Responses from cows fed diets
    containing fenthion of fentrothion - J. Dairy Sci. 55(6) 777-782.

    Kirca, A.C.  (1976)Information furnished by the Ministry of Food,
    Agriculture and Animal Husbandry - Turkey. Letter to WHO from
    Permanent Mission of Turkey, 20 January 1976.

    Magallona, E. (1977) Residues resulting from supervised trials
    - Submission on behalf of the Phillipines to FAO.

    Wallnofer, von P., Sohlemann, F. and Dehlmann, L. (1976) The effect of
    fenthion on the organism Rhizopus japonicus.
    Pflanzenschutz-Nachrichten Bayer 29/1976(3).

    Zadrozinska, J. (1972) A study of fenthion in selected plants (Polish)
    - Roca. Panstw. Zakl. Hig. 23 (4) 409-416.
    


    See Also:
       Toxicological Abbreviations
       Fenthion (ICSC)
       Fenthion (WHO Pesticide Residues Series 1)
       Fenthion (WHO Pesticide Residues Series 5)
       Fenthion (Pesticide residues in food: 1978 evaluations)
       Fenthion (Pesticide residues in food: 1979 evaluations)
       Fenthion (Pesticide residues in food: 1980 evaluations)
       Fenthion (Pesticide residues in food: 1983 evaluations)
       Fenthion (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)
       Fenthion (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)
       Fenthion (Pesticide residues in food: 1997 evaluations Part II Toxicological & Environmental)