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    ETHEPHON      JMPR 1977

    IDENTITY

    Ethephon has been adopted as a common name by the American National
    Standards Institute (ANSI), but not by the International Organization
    for Standardization (ISO).

    Chemical Name

    2-chloroethylphosphonic acid.

    Synonym

    Ethrel (R)

    Structural Formula

    CHEMICAL STRUCTURE 4

    Chemical properties

    a)   State: White waxy solid

    b)   Melting point: 144.5C

    c)   Solubility: very soluble in water, alcohol, acetone, propylene
         glycol and other polar solvents

    d)   Flammability: non-flammable

    Purity

    Company request disclosure to be withheld.

    EVALUATION FOR ACCEPTABLE DAILY INTAKE

    No toxicological information on ethephon was made available to the
    1977 Joint Meeting. Therefore no toxicological evaluation could be
    accomplished and no acceptable daily intake for humans was
    established.

    RESIDUES IN FOOD AND THEIR EVALUATION


        TABLE 1. United States Registered Uses for Ethephon

                                                                                                        

                      Application                                              Timing or
    Crop              Rate, kg,ha           Purpose                            Pre-harvest interval
                                                                                                        

    Apples            0.70-1.4              fruit loosening and                7-21 days
                                            uniform ripening
    Blackberries      2.8                          "                           3 days
    Blueberries       2.24                  uniform ripening                     -
    Cantaloupes       0.84                  fruit loosening                      -
    Cherries          1.4                   fruit loosening and                7-14
                                            uniform ripening
    Cranberries       1.68                  uniform coloring                     -
    Figs              1.12                  uniform ripening,                  14-21 days
    Filberts          1.96                         "                             -
    Lemons            0.1 kg/hl spray       degreening of fruit
                                            (Postharvest)
    Peppers           1.12                  uniform ripening and coloring        -
    Tangerines        1.39                  uniform coloring                     -
    Tomatoes          1.83                  uniform ripening                     -
    Pineapples        6.72                  flower bud development             6-8 months
                      1.12                  uniform ripening and fruit         7 days
                                            loosening
    Walnuts           1.4                   uniform ripening                   5-10 days
                                                                                                        

    

    USE PATTERN

    The Meeting was informed that ethephon is used in the United States,
    Canada, New Zealand, the United Kingdom, France, Australia and the
    Netherlands as a growth regulator. United States Registered Uses are
    shown in Table 1. Use patterns in other countries are generally
    comparable.

    In addition to the uses described in Table 1, the Meeting was informed
    that the product is used on blackcurrants in the United Kingdom and on
    glasshouse tomatoes in the Netherlands. Australia has under
    consideration proposed uses for peaches, blackcurrants and tobacco.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

    Residue data were available from the United States (in summary form),
    Canada, the Netherlands, the United Kingdom and France. Tables 2 and 3
    summarize the residues found on a variety of commodities and their
    by-products in the U.S.A. Pre-harvest intervals, concentration factors
    and application rates are also given.

    Table 4 contains a summary of residue values on blackcurrants from
    residue trials conducted in the U.K. and reported to the Meeting. The
    trials were carried out in the years 1969-1971.

    In other trials from the U.K. in 1971 on apples, all residues were
    reported as <0.5 mg/kg from spray concentrations of 750 mg/kg.
    Samples were taken at intervals after treatment ranging from 3 to 16
    days. At dosages of 1000 mg/kg and above, residues of about 1-3 mg/kg
    were found on pears. No residues were detected on gooseberries or
    tomatoes even on the day of treatment with spray concentration of 480
    and 250 mg/kg respectively.

    Supervised residue trials in France were reported to the Meeting. At
    spray concentrations of 480 mg/kg, initial deposits on apples were
    0.80 - 1.09 mg/kg and declined to 0.30 - 0.99 mg/kg on day 7. At 960
    mg/kg spray concentration initial deposits were 0.60 - 1.34 mg/kg,
    declining to 0.59 - 1.24 mg/kg on day 7.

    French residue trials on tomatoes were carried out at several spray
    concentrations (480, 720, and 960 mg/kg) and samples taken at
    intervals from 0 to 28 days. The residues showed no tendency to
    decline gradually in that period. There is apparently continuous
    absorption and translocation into the fruit until foliar deposits are
    exhausted or weathered, with peak residues occurring about the 10-15th
    day. Overall, residues were in the range 0.07 - 0.65 mg/kg.



        TABLE 2. Residues of ethephon in various commodities, resulting from supervised trials in USA

                                                                                                              

    Crop                 Application rate,       No. of          Pre-harvest            Residue range
                         a.i. kg/haa)            treatments      interval (days)          (mg/kg)
                                                                                                              

    Apples               0.37                       1               3 - 13              0.16 to 2.3
                         0.74                       1               3 - 13              0.48 to 4.5
                         0.56 to 2.8                1               3 - 19              0.12 to 4.5

    Blackberries         1.12 to 2.8 (1x)           1               0 - 4               0.4 - 23.4

    Blueberries          1.12 to 2.24 (1X)          1               7 - 14              0.9 - 12.9

    Canteloupes          0.89 to 1.79               1               3 - 6               0.08 - 0.46
    (1X = 0.84)          0.89 to 1.79               1               3 - 10              0.11 - 1.2
                         1.79                       1                 1                 1.8
                         1.79                       1                 8                 whole melon 0.21
                                                                                        rind  0.18
                                                                                        seeds 0.06
                                                                                        flesh 0.03

    Cherries             0.70 -2.8 (2X)             1               6 - 14              0.69 - 12.2
                         0.58 -2.8 (2X)             1               6 - 10              <0.01 - 8.1
                         0.58                       1                 1                 1.50 - 3.4

    Cranberries          1.12 - 2.8                 1               0 - 3               1.79 - 10.1
    (1X = 1.68)          1.12 - 2.8                 1               6 - 11              0.09 - 5.6
                         1.12 - 2.8                 1              14 - 21              <0.01 -0.78

    Figs                 0.70 - 2.8                 1                14                 0.84 - 4.4
                         0.70 - 2.8                 1                26                 0.47 - 2.6
                         1.05 - 5.25(b)             1              15 - 41              0.22 - 0.47

    TABLE 2. (Continued)

                                                                                                              

    Crop                 Application rate,       No. of          Pre-harvest            Residue range
                         a.i. kg/haa)            treatments      interval (days)          (mg/kg)
                                                                                                              
    Filberts             0.69 - 1.87                1              20 - 39              <0.01 - 0.16
    (1X  1.96)           2.8 -5.6                   1              19 - 20              0.04 - 0.31
                         2.8                        1                 7                 <0.01 - 0.01
                         1.87 - 2.06(c)             1              28 - 39              <0.01 - 0.14
                         2.8 - 4.2 (c)              1                 7                 0.04 - 0.07
                         5.6                        1                 7                 0.13 - 0.20

    Lemons               (1x) 0.1 - 0.2             1           post-harvest            0.6 - 1.9
                         kg/hl spray

    Peppers              0.84 - 1.4                 1               5 - 15              0.20 - 13.5
                         0.84 -1.12 (1x) (d)        1               5 - 8               9.13 - 28.7
                         0.84 -1.12 (d)             1                15                 <0.01 - 3.

    Tangerines           0.90 - 1.80 (1.33X)        1               3 - 9               Peel 0.33 -0.72
                                                                                        flesh
                                                                                        <0.01 - 0.10e)

    Tomatoes             0.478 - 2.24               1               3 - 10              0.08 - 1.7
    (1X = 1.83           0.478 - 2.24               1              12 - 16              0.03 - 1.9
                         0.93 - 2.4                 1              18 - 21              0.03 - 0.41

                         0.56 - 0.90                1               1 - 3               <0.01 - 0.47
                         0.56 - 0.90                1               4 - 6               0.02 - 1.2
                         0.56 - 0.90                1              12 - 16              0.11 - 0.29
                         1.23 - 1.88                1               8 - 10              0.18 - 1.2
                         1.23 - 1.88                1                14                 0.29 - 1.1

    Coffee Beans         120 - 240 mg/plant         1              13 - 30              <0.01 - 0.05
                         360 - 480 mg/plant         1              13 - 30              <0.01 - 0.07
                         600 - 960 (3x)mg/plant     1              13 - 30              <0.01 - 0.15

    TABLE 2. (Continued)
                                                                                                              

    Crop                 Application rate,       No. of          Pre-harvest            Residue range
                         a.i. kg/haa)            treatments      interval (days)          (mg/kg)
                                                                                                              


    Pineapples           2.24 -18 (2.5x)           1f)            6 months              <0.05
                         0.56                      1g)                7                 fruit 0.05 - 0.3
                                                                                        shell & core 0.1 - 0.3
                                                                                        whole fruit 0.03 - 0.3h)
                         1.12(1X)                  1g)               14                 fruit 0.05 - 0.7
                                                                                        shell & core 0.2 - 1.8
                                                                                        whole fruit  0.1 - 1.2
                         1.56j)                    2i)                7                 flesh 0.03 - 0.16
                         1.12j)                    2i)                7                 flesh 0.04 - 0.43
                         2.24j)                    2i)                7                 flesh 0.08 - 0.59
                         1.12j)                    2i)                7                 shell 0.11 - 0.54
                         2.24j)                    2i)                7                 shell 0.31 - 0.44


    Pineapple forage     1.12                      3k)                7                 0.80 - 2.19
    and fodder           2.24                      3k)                7                 1.75 - 5.35

    Walnuts              1.4                        1               7 - 36              0.04 - 0.08
                         2.1                        1              14 - 20              0.02 - 0.08
                         2.8                        1               5 - 7               <0.01 - 0.57
                         0.84                       1                 7                 <0.01 - 0.04
                         1.4                        1                 7                 0.01 - 0.06
                         0.84 1)                    1                 7                 <0.01 - 0.1
                         1.4 1)                     1                 7                 <0.01 - 0.04

    Apples
    (Canada)             300 mg/kg spray            1                 0                 1.59
                         300 mg/kg spray            1                10                 0.65
                                                                                                              

    TABLE 2. (Continued)

    a)   Numbers in parenthesis refer to the maximum
         registered application rate in the United States,
         e.g. 2X = 2 times the maxim= registered rate

    b)   Dried figs

    c)   Dried filberts

    d)   Chili peppers

    e)   Assuming that 25% of the weight of the whole tangerine
         is peel, the calculated level on the whole fruit from a
         value of 0.72 mg/kg on the peel is 0.18 mg/kg

    f)   Bud flowering use

    g)   Pre-harvest use

    h)   Calculated or actual values

    i)   One bud-flowering and one pre-harvest treatment

    j)   Treated with 1.12, 2.24, or 4.48 kg/ha to promote bud
         flowering 7 to 7 1/2 months prior to harvest then treated
         at pre-harvest rates given

    k)   One 1.12, 2.24, or 4.48 kg/ha treatment 7 to 7 1/2 months
         prior to harvest then one 2.24 kg/ha treatment 2 1/2 to 3 1/2
         months prior to harvest then one treatment at pre-harvest
         rates given

    l)   Dried walnuts


    

        TABLE 3. Residues in feed by-products (supervised trials in USA)

                                                                                                

                                                              Concentration factor
    Crop                         By-product                   in by-product
                                                                                                

    Lemons                       Dried lemon pulp                    1.2
                                 molasses                            1.5
                                 Lemon juice & oil            no concentration

    Apples                       Dried Apple pomace           no concentration

    Tangerines                   Dried tangerine peel                1.6

                                 Tangerine molasses                  4.3

    Pineapples                   Dried Pineapple bran         no concentration
                                                                                                
    

        TABLE 4. Average residues, corrected for recovery, mg/kg, in blackcurrants

                                                                                                      

    Time interval                                  SPRAY CONCENTRATION, mg/kg
    (days)
                                                                                                      

                           250                   500               375                750

    0                                                              1.6,1.8,2.6        2.9,3.9,3.5
                                                                   1.8                4.6

    1                                                              4.8,4.7,5.5        7.4,8.8,6.4

    2                                                              3.9,6.6            6.5,9.5
                                                                   4.1                5.9

    3                                            0.30              5.2,2.5            10.0,5.9

    4                                                              3.6,5.5,4.5        6.7,7.3,6.6

    5                      0.28,0.22             0.22,0.28

    6                      0.18                  0.54

    7                      0.56,0.22             0.48,0.20         3.2,3.3            8.2,4.8
                                                                                                      

    TABLE 5. Residues from supervised trials in the Netherlands
                                                                                                      
    Crop             Application          No.             Year               Interval        Residue
                        rate                                                  (days)         (mg/kg)
                                                                                                      
    Apples              0.67              1               1975                   7          0.71-1.14
                     kg a.i./ha
                        0.94              1               1975                   7          0.43-1.49
                     kg a.i./ha
    Tomatoes            0.012             1               1977                   3          1.1 -1.7
                     kg a.i./ha
                          "               1                 "                    7          1.0 -1.5
    Blackcurrants     250 mg/kg           1            1969, 1970                7          0.20-0.56
                      500 mg/kg           1            1969, 1970               5-7         0.20-0.54
                      375 mg/kg           1               1971                   0          1.6, 1.8
                        "  "              1                 "                    1          4.8, 4.7
                        "  "              1                 "                    2          3.9, 6.6
                        "  "              1                 "                    4          3.6, 5.5
                        "  "              1                 "                    7          3.2, 3.3
                      750 mg/kg           1                 "                    0          2.9, 3.9
                        "  "              1                 "                    1          7.4, 8.8
                        "  "              1                 "                    2          6.5, 9.5
                        "  "              1                 "                    4          6.7, 7.3
                        "  "              1                 "                    7          8.2, 4.8
    Tomatoes          480 mg/kg           1               1974                   0            0.07
                        "  "              1                 "                    3            0.12
                        "  "              1                 "                    7            0.44
                        "  "              1                 "                   10            0.24
                        "  "              1                 "                   15            0.32
                        "  "              1                 "                   21            0.18
                      720 mg/kg           1                 "                   28            0.19
                        "  "              1                 "                    0            0.08
                        "  "              1                 "                    3            0.19
                        "  "              1                 "                    7            0.27
                        "  "              1                 "                   10            0.52
                        "  "              1                 "                   15            0.55
                        "  "              1                 "                   21            0.25
                        "  "              1                 "                   28            0.23
                                                                                                      
    

    A country statement from the Netherlands contained reports on residue
    trials on currants, apples, tomatoes, pears, cherries and
    gooseberries. The analytical results did not differ significantly from
    those in the trials previously discussed. A summary of the typical
    residues found is given in Table 5.

    FATE OF RESIDUES

    In animals

    Metabolism studies using 14C-labelled ethephon were carried out on
    the rat and dog. The data demonstrated that ethephon is rapidly
    eliminated by both species. After 72 hours the rats and dogs retained
    < 1% of the ingested radioactivity. In both species 40-68% of the
    radioactivity was excreted as ethephon, 29-35% as ethylene, and less
    than 0.1 to 0.5% as carbon dioxide. This metabolism pattern is
    considered similar to that found in plants.

    In plants

    Radiotracer studies using 15C-labelled ethephon have been carried
    out on grapes, walnuts, pineapples, cherries, tangerines, oranges,
    tomatoes, filberts, figs, cantaloupes and apples. All of these studies
    consistently demonstrate that ethephon translocates in plants and
    exists in or on plants as the parent compound until degraded into
    ethylene, phosphate, and chloride ion. Thus the terminal residue of
    concern is the parent.

    Other studies have indicated the presence of a very labile conjugate
    of ethephon which produces the parent molecule under chromatographic
    conditions.

    In soils

    Studies conducted on soils indicate the same pathway for degradation
    found in animals and plants. When applied to the soil ethephon
    released ethylene gas. The presence of soil organisms does not appear
    to alter the pathway for degradation.

    In processing and cooking

    See "Evidence of residues in food in commerce or at consumption which
    follows.

    EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION

    Ethephon is not detected by the multi-residue screening procedures
    used in government market basket surveys and monitoring programmes and
    therefore no data for residues of ethephon in commerce in the United
    States are available.

    A survey carried out in the Netherlands in 1975 showed that of some 68
    samples of tomatoes analyzed (mainly greenhouse tomatoes), 34 samples
    had non-detectable residues, 16 samples showed residues ranging from
    0.05 to 1.0 mg/kg, and 18 samples had ethephon residues ranging from
    1.1 to 8.1 mg/kg. No indication of whether the tomato samples were
    washed was given. Similar results were obtained in a 1976 survey.

    Degradation studies on pineapples, tomatoes, grapes etc., indicate
    that washing, cooking or other preparation decreases the level of
    ethephon found on a commodity and therefore there would be little
    likelihood that ethephon residues would occur on a commodity at the
    time of consumption. This information is also supported by the fact
    that ethephon is not extremely stable.

    METHODS OF RESIDUE ANALYSIS

    Ethephon residues in crops are determined by a GLG method published in
    PAM II (1974). The method involves freeze-drying the samples, soxhlet
    extraction with methanol, concentrations, pH adjustment, precipitation
    of interfering materials, esterification with diazomethane and GLC
    analysis using a phosphrous-specific alkali thermionic detector. The
    method determines the parent only and can be used on a number of
    different crops.

    This method had been tested in government laboratories on pineapple.
    Depending on crop blanks the lower limit of detection is about
    0.05 mg/kg.

    A confirmatory procedure utilizing an alternative GLC column of
    different polarity and a microcoulometric detector is also published
    in PAM II (1974).

    APPRAISAL

    Ethephon is a growth regulator used to produce various beneficial
    effects on a variety of fruits, nuts, and vegetables. Information
    available to the Meeting indicated that national tolerances for
    ethephon have been established. by the governments of the USA, New
    Zealand, Netherlands, Canada and Australia.

    Ethephon must be absorbed and translocated in plants or fruit in order
    to produce the desired effects. Radio-tracer studies show that the
    compound is metabolized in plants to ethylene and phosphate and
    chloride ions. However, the parent compound itself is sufficiently
    persistent to require guideline levels (until maximum residue limits
    can be established) for fruits and vegetables in commerce. Animal
    studies show that it is rapidly eliminated from the body.

    Summaries of extensive residue trials in the USA submitted by the
    basic manufacturer to the US Government were made available to the
    Meeting. Country statements from Canada, the Netherlands, France and
    the United Kingdom contained results of supervised trials which
    generally agreed with the US findings. Additionally, the Netherlands
    and the UK reported on residue trials on blackcurrants which were
    adequate to support a recommendation for a guideline level for that
    commodity.


        National Tolerances Reported to the Meeting

                                                                                                            

    Commodity            United States         New Zealand    Netherlands      Canada         Australia

                                                                                                            

    Apples               5                     2              2                3
    Blackberries         30
    Blueberries          20
    Cantaloupes          2
    Cherries             10                                   1                               15
    Cherries, sour                                            1                2
    Cherries, sweet                                                            8
    Coffee beans         0.1
    Cranberries          5
    Figs                 5
    Filberts             0.5
    Lemons               2
    Peppers              30
    Pineapples           2
    Pineapples           3                                                                    2
    Fooder and
    forage
    Tangerines           0.5
    Tangerine hybrids    0.5
    Tomatoes             2                     1              1                3              2
    Walnuts              0.5
                                                                                                            

    

    Ethephon residues are determined by a "specific" GLC method which has
    been validated in government laboratories. The lower limit of
    determination is about 0.05 mg/kg. it is not detected by any of the
    multi-residue procedures used in the USA or Canadian Government
    surveillance programmes. Surveillance programmes in the Netherlands
    indicate that tomatoes in commerce may contain residues approaching 3
    mg/kg from glasshouse use.

    The necessary toxicological data required to allocate an ADI were not
    available to the Meeting. However, information relating to national
    use patterns, analytical methods and residue trials was sufficient to
    set guideline levels.

    EVALUATION

    The following guideline levels for ethephon are recorded.

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

    peppers                       30                       0

    blackberries                  30                       3

    blueberries                   20                       7-14

    cherries                      10                       7-14

    apples                        5                        7-21

    blackcurrants                 5                        0

    cranberries                   5                        0

    figs                          5                        14-21

    tomatoes                      3                        0

    pineapples                    2                        7

    cantaloupes                   2                        0

    lemons                        2                   (post-harvest)

    filberts                      0.5                      0

    tangerines                    0.5                      5-10

    walnuts                       0.5                      5-10

    coffee (beans)                0.1                       -

    FURTHER WORK OR INFORMATION

    REQUIRED (before an acceptable daily intake for humans (ADI) can be
    established and maximum residue limits (MRL) can be recommended)

    1. Submission of full toxicological data.

    DESIRABLE

    1. Country statements on national use patterns and supervised residue
    trials, and information on occurrence of residues on commodities in
    commerce.

    REFERENCES

    PAM II, (1974) Pesticide Analytical Manual, Vol. II, revised; U.S.
    Department of Health, Education, and Welfare, Food and Drug
    Administration.
    


    See Also:
       Toxicological Abbreviations
       Ethephon (Pesticide residues in food: 1978 evaluations)
       Ethephon (Pesticide residues in food: 1983 evaluations)
       Ethephon (Pesticide residues in food: 1993 evaluations Part II Toxicology)
       Ethephon (JMPR Evaluations 2002 Part II Toxicological)