ETHEPHON          JMPR 1978


         Residue aspects of ethephon were evaluated by the Joint
    Meeting in 1977 (FAO/WHO, 1978b) at which time only guideline
    residue levels could be proposed owing to constraints on data and
    the lack of an ADI. Some data on short term toxicological work and
    additional information on use patterns, residues from supervised
    trials and methods of analysis are summarized in this monograph

    Short-term studies


         In 1 90-day test, rats (8/group) were dosed by gavage with
    1500, 750, 375, 190, 90 and 45 mg/kg on five days per week. Death
    occurred at the highest dose. Reduced weight gain and some decrease
    in urinary pH occurred in the two highest dosage groups only. Food
    consumption did not differ in any of the groups. Hematology studies
    revealed no abnormalities. Urinary protein, sugar or sediment were
    unaffected, and serum glutamic-oxaloacetic-transaminase and
    leucine-aminopeptidase were within normal ranges. Relative liver,
    kidney, adrenal, spleen and thymus weights did not differ between
    test groups and control and no gross pathology was detected. In the
    1500 mg/kg dose group histological studies revealed some vaculation
    in liver parenchymal cells. A tendency towards diminished size of
    liver cell nuclei, an increased size of the Kupffer cells and some
    renal tubular necrosis was also observed at the highest dose.
    Exposures at the 375 mg/kg dosage or less were associated with
    little or no effects under the conditions tested (Weisbrod et al.,


         Ethephon was reviewed by the 1977 Joint Meeting (FAO/WHO,
    1978b) at which time it was reported that long-term studies were in
    progress the reports of which would be made available by 1978. The
    results of such studies were not available to the Joint Meeting. A
    short-term study was available to the Meeting.

         In a short-term 90-day study in rats, ethephon was
    administered by gavage at dosage levels varying from 0 to 1500
    mg/kg/day five days/week. Growth depression was noted at 750 mg/kg
    and above. Mortality and histopathological changes were observed at
    1500 mg/kg Clinical chemistry and gross examination of several
    tissues showed no specific adverse effects.

         The available data were insufficient to allocate an ADI.



         In Australia ethephon in used to initiate flowering of
    pineapple, peaches, tomatoes and apples, It has undergone trials
    for use as a harvest aid (to accelerate ripening and loosen fruits)
    in grapes, cherries, pears, and black currants. In the Netherlands
    it is used for sprout inhibition of bulb onions.

         Ethephon in available as a 480 g/l concentrate and in applied:

    (i)       to pineapple plants at 1 kg/2000 l or half
              this concentration (depending on the time of
              year) to initiate flowering; the pre-harvest
              interval in about 9 months;

    (ii)      to pineapple fruits at 2.2 kg/ha at 200g/100l
              (0.2%) concentration to accelerate ripening;
              it in applied one week before harvest;

    (iii)     to tomato fruits, pre-harvest, at 875g/ha at
              200g/100l concentration (0.2%) or half this
              concentration, to accelerate ripening of
              pink-red fruit, it is applied 7 days before

    (iv)      to apples at 24-48g/100l (0.24-0.48%)
              concentration to advance fruit maturity and
              coloring; it is applied 7-14 days prior to

    (v)       to peaches at 864g/ha at 200g/100l (0.2%)
              concentration to advance maturity; it is
              applied about 6 weeks before harvest;

    (vi)      to bulb onions at 500 l spray/ha in 280 g
              ai/100 l concentration to inhibit sprouting;
              it is applied 4 weeks before harvest.

    Post-harvest treatments

              Ethephon is applied to tomato fruits post-harvest as a
    192-288 g/100l (0.19-0.29%) concentration dip to ripen picked
    mature green fruits.


              Ciba-Geigy Australia, Ltd. (1978a) have made field trials
    with an ethephon formulation (48% liquid concentrate) on
    pineapples, tomatoes, apples, peaches, cherries, pears, grapes and
    black currants.

    The residues are summarized below. All residues were determined by
    an adaptation of the method of Bache (1970).

    Pineapples       (i)     Residues in fruit following spraying of
                             plants to initiate flowering: single
                             trial data, 1971; no residues were
                             detected (limit of detection, 0.05 mg/kg)
                             in the whole fruit or flesh of pineapples
                             9 months after the plants had been
                             sprayed with 6 concentrations of ethephon
                             varying from 5 to 25g/100l. Each plant
                             was treated with 28ml of spray, i.e. the
                             actual amount of ethephon applied per
                             plant ranged from 14 to 70 mg. All
                             treatments were replicated 3 times, and
                             the plot size was 20 pineapples plants. 2
                             plants per plot were sampled.

                     (ii)    In a 1972 trial, in which ethephon was
                             applied to ripening fruits (a fortnight
                             before harvest) in concentrations of 50,
                             100 and 200 g/100l at 1120l/ha the
                             residues found ranged from 0.81-0.28
                             mg/kg one day after treatment to
                             0.28-0.12 mg/kg fifteen days after.

    Tomatoes          (i)    Pre-harvest spraying, 1972: after a single
                             treatment at 896g/ha using an ethephon
                             concentration of 400g/100l (0.4%) the
                             residues found in whole fruit bush
                             tomatoes, sampled 1, 4, 7 and 11 days
                             after application, did not exceed 0.5

                     (ii)    Post-harvest dip 1976 trial: after
                             dipping three concentrations of ethephon,
                             (100, 200 and 300g/100l) the tomatoes
                             were analysed 0, 3, 4, 7, 10 and 14 days
                             after treatment. The initial residues,
                             1.3, 2, 3 and 4 mg/kg, were in proportion
                             to the ethehpon concentrations applied,
                             and they hardly varied during the 14

    Apples                   In a 1974 trial In New South Wales,
                             three varieties of apples were sprayed
                             some 3 weeks before harvest. Following
                             application of 50g/100l ethephon
                             concentration at 13.5 litres/tree to two
                             of the varieties the residue found ranged
                             from 0.75-1.1 mg/kg immediately after
                             treatment to 0.25-0.28 mg/kg 21 days
                             later. The third variety as sprayed with

                             ethephon at 25g/100l concentration and
                             22.5 litres/tree and a single
                             determination nine days later showed
                             0.26-0.72 mg/kg residue.

    Peaches                  In a 1974 trial in NSW, a variety of
                             peach was sprayed with two concentrations
                             of ethephon, 20g/100l and 40g/100l, at
                             27-31.5 litres/tree some two to three
                             weeks before harvest. The residues found
                             16 and 23 days after application ranged
                             from 0.26-0.72 mg/kg (lower rate - higher
                             rate of application) to 0.24 mg/kg (lower
                             rate), respectively.

    Cherries                 In a 1972 trial in Victoria, a variety
                             of cherry as sprayed with two
                             concentrations of ethephon, 25g/100l and
                             50g/100l, at 23-27 litres/tree one week
                             before harvest. The residues found in the
                             fruit flesh ranged from 3.6-5.1 mg/kg
                             (low rate - high rate of application)
                             immediately after spraying to 9.5 - 14.3
                             mg/kg (low-high rates) fourteen days

    Grapes           (viii)  Two trials were made in NSW in 1975. In
                             one, ethephon at 80g/100l (0.08%) was
                             applied to grapes at 10001/ha five days
                             before harvest; the mean residues found
                             in the fruit ranged from 7.2 mg/kg
                             immediately after application to 4.2
                             mg/kg at harvest. In the other, two
                             concentrations of ethephon, 50 and
                             100g/100l were sprayed to `run-off' on
                             fruiting vines seven days before harvest;
                             mean residues found in the fruit juice at
                             harvest ranged from 3.8-8.5 mg/kg (low
                             rate - high rate of application).

    Black-currants   (ix)    In a trial in Tasmania in 1974, 6g/100l
                             ethephon was sprayed on black currants
                             fruiting-bushes at 600ml/bush;, residues
                             found in the fruit harvested 1, 2, 4, 7
                             and 12 days after application hardly
                             varied, ranging from 0.11-0.18 mg/kg.

    Onions           (x)     In the Netherlands in 1977, 4 plots of
                             onions were treated once each with 0,
                             960, 1440 or 1920 kg ai/ha using a 480 g
                             ai/l liquid formulation. At 20 days after
                             application, residues were 0.1 mg/kg
                             (mean of 3 replicates) for the untreated

                             samples, 0.1 mg/kg (mean of 3) for the
                             960 kg treatment, 0.14-0.35 mg/kg for the
                             1440 kg treatment, and 0.14-0.35 mg/kg
                             for the 1920 kg treatment.


    In plants

         In connection with the development of a new method of analysis
    for ethephon in tomatoes, cherries and apples, Hurter et al.,
    (1978) described results obtained when tomatoes were treated once
    in the field with a 0.2% solution at a time when fruits of the
    first cluster turned from green to yellow. A steady increase in
    ethephon concentration in treated tomatoes occurred for
    approximately seven days post-treatment rising from about 3 mg/kg
    to about 7 mg/kg then declining slowly thereafter for about 2
    months. This observation was interpreted as indicating the systemic
    transport of ethephon from leaves into the fruit. The
    characteristic increase in ethephon residues were found also in
    apples and cherries within 2 and 8 days after application, reaching
    maximum values of 1.2 mg/kg in apples and 4.1 mg/kg in cherries.


         No new information was available to the Meeting.


         Information on two adaptations of the Bache method and a
    completely new rapid method for residues in tomatoes, cherries, and
    apples was available to the Meeting.

         Ernst et al., (1976) developed a rapid method for residues of
    ethephon in tomatoes by changing the extraction step and
    eliminating the clean-up step of the Bache method. Samples were
    extracted with ethyl acetate and the extract was methylated with
    diazomethane, decolourized with carbon and analysed by GC with a
    flame photometric detector. Recoveries ranked from 78 to 98% at the
    0.1 to 11 mg/kg level and the limit of determination was 0.1 mg/kg.

         In Australia, the Bache method was modified to be suitable for
    a large range of crops by Ciba-Geigy Australia, Ltd. (1978b). The
    macerated crop was extracted with methanol and acetone was used to
    precipitate some interfering co-extractives and dry the extracted
    residue. The residue was then methylated under acidic conditions
    with diazomethane and analysed by CG with a thermionic detector.
    Recoveries at 0.1 to 5 mg/kg levels ranged from 70-100% for a wide
    variety of crops with an overall limit of detection of 0.05 mg/kg.

         Hurter et al., (1978) developed a new and rapid method for
    ethephon residues based on degradation to ethylene at high pH
    values. The ethylene gas is determined by gas-solid chromatography

    with a flame-ionisation detector using head-space sampling
    techniques. The extraction and purification steps of other
    procedures (see above) are omitted. Results are consistent with the
    direct determination of methylated ethephon by GLC. The natural 
    ethylene content of fruit was found to be less than 5% of that which 
    can be expected from residues of ethephon. However, this limits the 
    level of determination to about 0.1 mg/kg ethephon, whereas the 
    absolute limit would be about 0.002 mg/kg. The method has sufficient 
    merit to warrant further investigation and validation for possible
    regulatory use for ethephon.


         The following list of maximum residue limits currently in
    force in Australia was available to the Meeting.

    Crop                Limit, mg/kg   Pre-harvest interval

    Cherries            15             7 days
    Pineapples          2              7 days
    Tomatoes            2              7 days
    Tomatoes            5              (Provisional for Post-harvest use)
    Black currants      1              7 days
    Apples              1              7 days
    Peaches             0.5            6 weeks
    Wine grapes         10             (provisional)


         The Joint Meeting evaluated ethephon in 1977. Only guideline
    residue levels could be recorded owing to insufficient data for
    allocating an ADI and inadequate data on residue levels from field

         New information was available to the Meeting on use patterns,
    residues resulting from supervised trials, and established maximum
    residue limits in Australia and the Netherlands. Data on peaches,
    onions and grapes which were not included in the previous
    evaluation, were sufficient to record additional guidelines residue
    levels for these commodities.

         Information was available on modified and improved methods of
    residue analysis. The modifications to the previous method have the
    merit of shortening or eliminating some of the procedures and
    should be further studied with a view to regulatory use. The new
    method developed by Hurter et al., (1978) which measures the
    ethylene gas liberated by ethephon under basic conditions, although
    indirect, has considerable promise for the rapid screening of
    fruits and vegetables and should be thoroughly investigated as a
    possible replacement for existing methods.


         The following guideline levels are additional to those
    previously recorded.

    Commodity           Guideline level, mg/kg   Intervals on which
                                                 levels are based

    Grapes              10                       7 days
    Onions (bulb)       0.5                      4 weeks
    Peaches             0.5                      6 weeks



    1.   Additional and more comprehensive residue data resulting from
    field trials on commodities not included in present recommendations
    and for which registered uses exist in various countries.


    Anonymous.     Information paper on ethephon from Australia.

    Anonymous.     Information paper on ethephon from the Netherlands.

    Bache, C.A. J.A.O.A.C. 53 (4) 730-732.

    Ciba-Geigy Australia, Ltd. Reports on field trials of ethephon in
    (1978a)        Australia. Attachments I through VIII.

    Ciba-Geigy Australia, Ltd. R. & D. Analytical Method No. 110A, The
    (1978b)        Determination of Ethephon Residues in Crops.

    Ernst, G.F. and Anderegg, M.J.P.T. Rapid Gas-Liquid Chromatographic
    (1976)         Method for Determining Residues of Ethephon
                   (2-Chloroethyl Phosphoric Acid) in Tomatoes.
                   J.A.O.A.C. 59 (5): 1185-1187.

    FAO/WHO. Working paper on ethephon prepared by the FAO Panel on
    (1978b)        Pesticide Residues and the environment.

    Hunter, J., Manser, M. and Zimmerli, B. A Rapid and Simple
    (1978)         Method for the Determination of Residues of
                   2-Chloroethyl Phosphoric Acid (Ethephon) in
                   Tomatoes, Cherries and Apples. J. Agric. Food Chem.
                   26 (2): 472-475.

    Weisbrod, D., Leine, J. and Ponsald, W. Untersuchungen zur
    (1973)         Toxizitat des Präparats; CKB 1080 Wirkstoff
                   (Ethephon); 90-Tage-Test an wachsenden Ratten. VEB
                   Chemisch-Pharmazentisches Werk Oschersleben
                   Forachunge-und-Entwicklungsstelle Blankenburg
                   (Harz) and CKB Bittefeld (CDR). Unpublished report.

    See Also:
       Toxicological Abbreviations
       Disulfoton (ICSC)
       Disulfoton (WHO Pesticide Residues Series 3)
       Disulfoton (WHO Pesticide Residues Series 5)
       Disulfoton (Pesticide residues in food: 1979 evaluations)
       Disulfoton (Pesticide residues in food: 1981 evaluations)
       Disulfoton (Pesticide residues in food: 1984 evaluations)
       Disulfoton (Pesticide residues in food: 1991 evaluations Part II Toxicology)