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TRADE OR OTHER NAMES: The active ingredient phosalone is found in a variety of commercial insecticides. Trade
names for products containing phosalone include Azonfene, Benzofos, Rubitox, Zolone and RP 11974 (112, 116, 174). The
common name phosalone is generally recognized, except in the Soviet Union, where the common name benzphos is used (2,
REGULATORY STATUS: Phosalone is no longer for sale in the U.S. (114). Phosalone was a general use pesticide
(GUP). Products containing phosalone had the Signal Word "Warning" on their label.
CHEMICAL CLASS: organophosphate insecticide
INTRODUCTION: Phosalone was introduced in 1963 by Rhone-Poulenc company as a nonsystemic insecticide and
acaricide for use on deciduous fruit trees, market garden crops, cotton, potatoes and rape (2,125). It is a broad-spectrum
pesticide with rapid killing ability. Approximately 12-20 days control may be expected (114).
Phosalone is a member of the organophosphate family of insecticides. It is used as both an insecticide and acaricide. It
comes in emulsifiable concentrate, wettable powder and dust formulations (117). It is used on nut crops, citrus, pome fruits,
stone fruits, grapes, potatoes, artichokes, roses and arborvitae (174). It is active against the red spider mite on apples and
pears. It controls a wide range of caterpillars and beetles on crops of economic importance as well as a number of hemiptera
and hymenoptera (120).
- Acute Toxicity: Phosalone is a compound of moderate toxicity (2, 125). The acute oral LD50 values ranged between
82-205 mg/kg for male rats; and between 90-170 mg/kg for female rats (117, 173, 174). The acute dermal LD50 values
for rats ranged between 350 mg/kg and 390 mg/kg (173, 174). The acute percutaneous LD50 for rats is 1,500 mg/kg
(111). Acute oral toxicities reported for mice ranged between 73 - 205 mg/kg (116, 173); between 82-380 mg/kg for
guinea pigs (111, 116, 173); 112 mg/kg for cats (2, 125); and greater than 1,600 mg/kg for dogs (146). Studies on
rabbits exposed to phosalone reported the dermal LD50 to be greater than 2,000 mg/kg and the percutaneous LD50 to
be greater than 1,000 mg/kg (111, 173). The primary dermal irritation was found to be mildly irritating to intact and
abraded skin and moderately irritating to the skin and eyes (2, 125, 174).
- Chronic Toxicity: Feeding of phosphate to rats at dietary levels of 25, 50 and 250 ppm and to dogs at 100, 200 and
1,000 ppm resulted in dosage-dependent inhibition of red blood cell and plasma cholinesterase, but no signs of illness. In
rats, 50 ppm or about 2.4 mg/kg/day was the highest level with no effect on cholinesterase. In fact, rats and dogs
tolerated oral dosages of 7.5 and 15 mg/kg/day for a month, and rats tolerated a dietary level of 250 ppm (about 12
mg/kg/day) for 1 year with no abnormality of growth, behavior, or hematology. Rats and cats tolerated repeated
exposure to an atmospheric concentration of 9.34 mg/cubic meter (2, 125). Another two-year feeding study on rats
receiving 250 mg/kg diet and on dogs receiving 290 mg/kg diet indicated neither group suffered ill effects (111). Dogs
fed doses of 0, 100, 200 and 1,000 ppm for two years showed vacuolation and histological changes of the smooth muscle
cells of the small intestine, and the ratios organ/body weight were increased, i.e. liver/body weight, at the 1000 ppm
level. Effects on cholinesterases were evident at all levels of feeding compared to the control group. Rats fed 0, 25, 50,
and 250 ppm dietary levels for two years exhibited depression of plasma cholinesterase at 50 ppm but not at 25 ppm
- Reproductive Effects: Oral administration of a 30% phosalone formulation to rats at doses up to 50 mg/kg/day on days
6 through 15 of gestation did not produce maternal toxicity (2, 125). Phosalone was found to have no effect on
reproduction in rats at doses of 0, 25 and 50 ppm (146).
- Teratogenic Effects: Oral administration of a 30% phosalone formulation to rats at doses up to 50 mg/kg/day on days 6
through 15 of gestation did not produce teratogenic effects (2, 125). Phosalone was not found to be teratogenic in
chickens, rats or rabbits (146).
- Mutagenic Effects: No information currently available.
- Carcinogenic Effects: A 104-week feeding study was conducted on mice. Fifty animals per sex were used. The dietary
doses given were 0, 5, 50, and 100 ppm. Female mice demonstrated an increased incidence of leiomyomas and
leiomyosarcomas of the uterus and of the Harderian gland adenomas (175).
- Organ Toxicity: No information currently available.
- Fate in Humans and Animals: In general, the biotransformation of phosalone is similar to that of other organic
phosphorous compounds. However, in studies where rats were given a single dose of labeled phosalone, 65.4 % of the
labeled carbon was recovered within 4 days as carbon dioxide in the expired air, while only 32.4% was excreted in the
urine and feces (2, 125). Phosalone is rapidly absorbed and excreted by mice following oral administration. Within 24
hours, less than 1 percent phosalone residues were found in the body. Phosalone is a weak inhibitor of cholinesterase. Its
oxygen analog is 2-3 times more active, especially in inhibiting serum cholinesterase (146). No clinical effect was
observed, and no phosalone or metabolite was found in the urine of fourteen men working in an orange grove beginning
14-17 and 21-23 days after the application of phosalone at a rate of 13.5 kg/ha. Plasma cholinesterase also remained
normal. The red cell cholinesterase level was depressed by 15% compared to that of the control group on day 15, but
returned to normal on day 17 (2, 125). A study of peach pickers indicated that in spite of estimated dosage rates as high
as 14 mg/person/hour, the red cell cholinesterase was inhibited only about 4%. It was estimated that 98-99% of the
workers' exposure was dermal, mainly to the hands and upper extremities. Four of six workers exposed to air
concentrations of 5.32 mg/cubic meter had their acetyl-cholinesterase depressed by only 16 to 29% (2, 125).
- Effects on Birds: Delayed neurotoxicity was negative in hens (174). Acute subcutaneous LD50 for chickens is 350
mg/kg (146) The avian oral toxicity indicated phosalone was slightly toxic to waterfowl; the acute oral LD50 for
mallards was greater than 2,150 mg/kg (174). The oral toxicity for pheasants was 290 mg/kg (111). The 8-day avian
dietary toxicity indicated phosalone was slightly toxic to waterfowl and upland game birds. Subacute toxicity for mallard
ducks was 1,659 ppm and 2,033 ppm for bobwhite quail (174).
- Effects on Aquatic Organisms: The 96-hour freshwater fish acute toxicity found phosalone to be very highly toxic to
warmwater fish and highly toxic to coldwater fish. The acute LC50 for bluegill sunfish was 0.05 ppm; 0.63 ppm for
rainbow trout (174); and 3.4 ppm for harlequin fish (27). Other LC50 values for phosalone indicated the toxicity for
goldfish was 2 mg/l; 0.11 mg/l for bluegill sunfish; and 0.3-0.63 mg/l for rainbow trout (117). One-fifth of the 24-hour
LC50 values caused hemorrhage in bluegills (122). The 48-hour freshwater invertebrate toxicity indicated phosalone to
be very highly toxic to aquatic invertebrates. The acute value for Daphnia magna was 0.0012 ppm (174). Immediate
toxicity to crustaceans is considered very high (115).
- Effects on Other Animals (Nontarget species): Phosalone rates of 700 g/ha were not found to be hazardous to
honeybees, provided they were not actively foraging at the time of spraying (111). Insecticides, one of which was
phosalone, applied to host eggs at field rates in the laboratory were highly toxic to Trichogramma brasiliensis released on
the eggs, causing 84-100% mortality in 24 hours. However, percentage parasitism after 4 days was higher with
phosalone (36 - 73%) than with other insecticides studied, and emergence from treated host eggs did not appear to be
affected. Phosalone had little or no effect on adults or cocoons of Apanteles plutellae (121).
- Breakdown of Chemical in Soil and Groundwater: Phosalone rapidly degraded (t1/2 = 3-7 days) in flooded
Metapeake loam and Monmouth fine sandy loam. Mineralization to carbon dioxide accounted for only 10% of the loss
(117). The primary degradative pathway proceeded by oxidation of phosalone to give phosalone oxon. Subsequent
cleavage of the O, O-diethyl methyl phosphorodithioate linkage gave 6-chloro-2-benzoxazolinone (117). Phosalone is
stable at pH 5 and 7, but is hydrolyzed at a pH of 9 with a half-life of 9 days (174). Phosalone does not move in soil and
degrades rapidly when compared to parathion (114). Aerobic soil metabolism studies demonstrate half-life values of 1-7
days. Field dissipation studies showed half-life values of 1-9 weeks. Phosalone was essentially immobile in a soil column
test. Based on this preliminary data, phosalone appears unlikely to contaminate groundwater (174).
- Breakdown of Chemical in Surface Water: Phosalone rapidly dissipates in untreated waters (174).
- Breakdown of Chemical in Vegetation: Phosalone degrades in plants to chlorbenzoxazolone, formaldehyde, and
diethyl phosphorodithioate (117, 146). It persists on plants about 14 hours, being converted to the corresponding
phosphorothioate which is rapidly hydrolyzed (111). Phosalone is not phytotoxic under normal conditions (120).
PHYSICAL PROPERTIES AND GUIDELINES
Phosalone is stable under normal storage conditions. It is compatible with most other pesticides and is noncorrosive. It is
incompatible with alkaline materials such as calcium arsenate and lime sulfur (2, 125). Phosalone emits toxic fumes of
chlorine, phosphorus, nitrogen, and sulfur oxides when heated to decomposition (117).
- Appearance: colorless crystals with a garlic-like odor (117, 2)
- Chemical Name: S-6-chloro-2, 3-dihydro-2-oxobenzoxazol- 3-ylmethyl O, O-diethyl phosphorodithioate (IUPAC);
S-[(6-chloro-2-oxo-3(2H)-benzoxazolyl)methyl] O, O-diethyl phosphorodithioate (CA); 3-(O, O-diethyl-
dithiophosphorylmethyl)-6-chlorobenzoxazolone (13); O,O-diethyl-S-(6-chloro-2-oxobenzoxazolin-3-yl-methyl)-
phosphorodithioate (2, 125)
- CAS Number:2310-17-0 (13, 112, 113, 117, 174) 2279-71-2 (116)
- Molecular Weight: 367.82 (116)
- Water Solubility: ca. 0.01 g/l (13); 10 g/l (111); 0.0010 at 20 degrees C (113); 1.2, 2.6 and 3.7 mg/l at 10, 20 and 30
degrees C respectively (117); 10 mg/l at room temperature (111)
- Solubility in Other Solvents: Soluble (ca. 1000 g/l) in ethyl acetate, acetone, acetonitrile, benzene, chloroform,
methylene chloride, cyclohexane, dioxane, methyl ethyl ketone, toluene, xylene (all at 20 degrees C) (13, 113, 146). In
methanol and ethanol, ca. 200 g/l at 20 degrees C (13, 117)
- Melting Point: 45-48 degrees C (13, 122, 146, 2); 117-118 degrees F (47-48 degrees C) (113)
- Vapor Pressure: very low (at 20 degrees C, practically negligible) (13); negligible at room temperature (111, 111, 113,
2) 5.03 x 10 to the minus 7 mmHg at 25 degrees C (117)
- Partition Coefficient: 3.77 - 4.38 (117)
- Adsorption Coefficient: 3.41 (calculated) (117)
- ADI: 0.006 mg/kg b.w.(146)
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
Rhone Poulenc Ag. Co.
P. O. Box 12014
Research Triangle Park, NC 27609
References for the information in this PIP can be found in Reference List Number 5
DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide
product label/ing or other regulatory requirements. Please refer to the pesticide product label/ing.