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3 EXTOXNET PIP-E THEPI-ION (—'%,p://ace.orst.edu/cgi-bin/mfs/01/pips/ethephon,litni M The doses were administered in feed at 0, 15.5, 156 or 1630 mg/kg/day to CD-1 mice for 78 weeks. No dose-related evidence of carcinogenicity/oncogenicity was reported (314). • Organ Toxicity: No information currently available. • Fate in Humans and Animals: No information currently available. ECOLOGICAL EFFECTS • Effects on Birds: Data indicate that technical-grade ethephon is slightly toxic on an acute oral basis to bobwhite quail, and slightly toxic on a subacute dietary basis to bobwhite quail and mallard ducks. The acute oral LC50 in bobwhite quail is from 596 to 804 mg/kg. The acute oral LC50 is 3,750 ppm for mallard ducks and greater than 2,160 ppm in bobwhite quail. The average acute oral toxicity for formulated products is greater than 10,000 ppm in bobwhite quail, or practically j non-toxic (315, 316). Another source reported the oral LD50 for bobwhite quail to be 1,000 mg/kg i (242). The chronic toxicity LC50 for birds was reported to be 804 mg/kg for quail and 3,750 ppm for ducks (223); and the LC50 (8 days) for mallard ducks was greater than 10,000 mg/kg diet. Effects on Aquatic Organisms: Laboratory and field studies indicate that ethephon is slightly toxic to fish. Studies indicated LC50 values for fish-of 170 mg/1 for rainbow trout; and 180 mg/l for bluegill sunfish. Also, a 96-hour LC50 for rainbow trout ranged from 254 mg/l to 350 mg/l and for bluegill sunfish 222 mgll to 300 mg/1 (Worthing and Hance, 1991) (1, 242,316). • Effects on Other Animals (Nontarget species): Two studies using ethephon were conducted in humans. In the first study, some symptoms characteristic of anticholinesterase activity were observed. Five humans of each sex were dosed with ethephon at an average dose level of 1.8 mg/kg/day. Subjects receiving the test compound reported the following symptoms and/or signs; G sudden onset of diarrhea or an urgency of bowel movements, stomach cramps or gas and increased urgency or frequency of urination, and either an increase or decrease in appetite. None of the control subjects had complaints similar to,the test group. Plasma CHE and RBC CHE activities were similar to or higher than initial values in test subjects (315). In the second human study, 10 humans of each sex were administered ethephon at 0.5 mg/kg/day for 16 days, followed by a 2-week recovery period. Dose related effects occurred in plasma cholinesterase activity, but not in red blood cell cholinesterase activity. The effect was reversible within 15 days. When the control group and test groups were compared, the decreased plasma cholinesterase activity was statistically significant. No dose-related effects were seen in hematology, blood chemistry, or urine analysis. Based on this study, the NOEL for plasma cholinesterase inhibition in humans is less than 0.5 mg/kg/day(315). Ethephon usage has resulted in four cases of skin injury(irritation) reported from 1980 through 1986 in California due to exposure to field residues (315). Ethephon is considered relatively non-toxic to honeybees (1, 315). ENVIRONMENTAL FATE • Breakdown of Chemical in Soil and Groundwater: Ethephon was found to have low to moderate mobility in soils ranging in texture from loamy sand to peat and silt loam based on soil thin layer chromatography tests. Therefore, the potential for contamination of groundwater appears to be low . :.1,_ to moderate (315). In sozi rapi adation to tphosphoric acid, ethylene, and chloride ions was irepor-ted-(Hartley and Kidd, 1987) (1,302). • Breakdown of Chemical in Surface Water: No information currently available. • Breakdown of Chemical in Vegetation: In plants, ethephon rapidly degrades to phosphate, ethylene, and chloride (1, 315). Ethephon and the ethylene gas it produces are the major metabolites in plants (315). Residues of monochloroacetic acid may be found in ethephon-treated commodities. Monochloroacetic acid is a potential degradation product of an impurity in ethephon, monochloroethyl ester of(2-chloroethyl)-phosphoric acid (315). i of 4 1/26/008:58 AM k