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 FormulaChemical properties a) State: White waxy solid b) Melting point: 144.5°C 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)