SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 732116
CASRN 732-11-6
SynonymsPhosmet
Phosphorodithioic acid, O,O-dimethyl ester, S-ester with N-(mercaptomethyl)phthalimide
Imidan
Analytical Methods EPA Method 622.1
EPA Method 8141
Molecular FormulaC11H12NO4PS2

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use INSECTICIDE FOR HORNFLIES ON BEEF CATTLE & FOR CATTLE GRUBS; FOR WEEVILS ON SWEET POTATOES IN STORAGE & ON ALFALFA /USE ON VARIETY OF CROPS INCL ALFALFA, ALMONDS, APPLES, APRICOTS, CHERRIES (TART), CITRUS, CORN, COTTON, CRANBERRIES, PECANS, BLUEBERRIES, GRAPES, NECTARINES, PEACHES, PEARS, PEAS (PACIFIC NORTHWEST), POTATOES, PLUMS/PRUNES & CERTAIN DECIDUOUS SHADE & ORNAMENTAL TREES & WOODY EVERGREENS. ACTIVE AGAINST A WIDE RANGE OF INSECTS SUCH AS ALFALFA WEEVIL, BOLL WEEVIL, CODLING MOTH, LEAFROLLERS, PLUM CURCULIO, GRAPE BERRYMOTH, ORIENTAL FRUIT MOTH, & MANY OTHERS. ALSO REGISTERED FOR USE ON ANIMALS FOR GRUBS, LICE, TICKS, SCABIES, MITES. Control of lepidopterous larvae, aphids, psyllids, fruit flies, and spider mites on pome fruit, stone fruit, citrus fruit, and vines; Colorado beetles on potatoes; boll weevils on cotton; olive moths and olive thrips on olives; blossom beetles on oilseed rape; leaf beetles and weevils on lucerne; European corn borers on maize and sorghum; sweet potato weevils on sweet potatoes in storage. Non-systemic acaricide and insecticide, used on top fruit citrus, grapes, potatoes and in forestry at rates (0.5-1.0 kg ai/hectare) such that it is safe for a range of predators of mites and therefore useful in integrated control programs. It is also used to control mites and warble fly of cattle.
Consumption Patterns 50% AS AN INSECTICIDE FOR WEEVILS ON ALFALFA, ON FRUIT, ON POTATOES & FOR CATTLE GRUBS & HORN FLIES ON BEEF CATTLE; 50% AS AN INSECTICIDE FOR WEEVILS ON SWEET POTATOES IN STORAGE, AND ON WOODY SHRUBS, TREES & VINES (1976)
Apparent Color OFF-WHITE CRYSTALLINE SOLID; Colorless crystals
Odor OFFENSIVE ODOR
Melting Point 71.9 DEG C
Molecular Weight 317.32
Density 1.03 at 20 deg C/4 deg C
Environmental Impact Phosmet's use a non-systemic insecticide releases the compound directly to the environment through applications in sprays, wettable powders and other routes of application. If released to the atmosphere, phosmet will degrade rapidly in the vapor-phase by reaction with photochemically produced hydroxyl radicals (half-life of about 2.6 hr). Particulate-phase phosmet and aerosols released to air during spray applications of phosmet insecticides will be physically removed from air by dry and wet deposition. If released to moist soil or water, phosmet can degrade through aqueous hydrolysis. Hydrolysis half-lives of 4 hr to 3.8 days have been observed at pHs of 8.0 to 8.3 and temperatures of 4 to 21 deg C; at 20 deg C, hydrolysis half-lives of 13 days (pH 4.5), 7 days (pH 6.1), and 7.1 hr (pH 7.4) have been observed. Insufficient data are available to access the relative importance of biodegradation in soil or water. A reported Koc value of 820 suggests low soil mobility; however, phosmet has been detected in leachates collected near a pesticide manufacturing plant. The US Dept of Agric's Pesticide Properties Database lists a soil half-life of 19 days. The persistence half-life of phosmet applied to foliage (alfalfa, peach, bermuda grass, corn, soybean) is reported to vary from 1.2 to 6.5 days. Occupational exposure occurs through dermal contact and inhalation of sprays, especially to workers applying the compound as an insecticide. Since phosmet has been detected in U.S. foods, exposure to the general population may occur through consumption of foods containing phosmet residues.
Environmental Fate TERRESTRIAL FATE: Since phosmet hydrolyzes readily in water(1-2), it may undergo hydrolysis in moist soil; hydrolysis increases with alkalinity(1-2), so the degradation rate of phosmet in soil will probably increase with alkalinity. In one soil persistence study (pH 6.2), phosmet had a soil half-life of 51-60 days in sealed vials . The US Dept of Agric's Pesticide Properties Database lists a soil half-life of 19 days for phosmet . The persistence half-life of phosmet applied to foliage (alfalfa, peach, bermuda grass, corn, soybean) is reported to vary from 1.2 to 6.5 days . The enhanced disappearance from plant leaves may be due to photodegradation; rapid photolysis on silica and apples has been observed(6). Based upon a Koc of 820 , phosmet is expected to have low mobility in soil(4,SRC); however, it has been detected in leachates collected near a pesticide manufacturing plant(7). Insufficient data are available to assess the relative importance of biodegradation in soil. AQUATIC FATE: Hydrolysis is a dominant degradation process for phosmet in water; various studies have observed rapid hydrolysis in alkaline waters(1-4). Hydrolysis half-lives of 4 hr to 3.8 days have been observed at pHs of 8.0 to 8.3 and temperatures of 4 to 21 deg C(1-4); at 20 deg C, hydrolysis half-lives of 13 days (pH 4.5), 7 days (pH 6.1), and 7.1 hr (pH 7.4) have been determined(1-2). In one screening study, however, hydrolysis rates of the wettable powder formulation of commercial phosmet were slower than found in other hydrolysis studies . Insufficient data are available to assess the relative importance of biodegradation in water. Volatilization from water and bioconcentration are not expected to be important fate processes. ATMOSPHERIC FATE: Based upon a reported vapor pressure of 4.9X10-7 mm Hg at 20-25 deg C , phosmet can exist in both the vapor and particulate-phases in the ambient atmosphere(2,SRC). It will degrade rapidly in the vapor-phase by reaction with photochemically produced hydroxyl radicals with an estimated half-life of about 2.6 hr(3,SRC). Particulate-phase phosmet and aerosols released to air during applications of phosmet insecticides will be physcially removed from air by dry and wet deposition.
Drinking Water Impact DRINKING WATER: An analysis of Ottawa, Canada tap water (sampling date not reported) did not detect (detection limit of 1 ng/l) any phosmet . GROUNDWATER: Phosmet was not detected (detection limit of 5.0 ppb) in ground water samples collected from 54 wells used for municipal and private water supplies in California . EFFL: Leachate samples collected near a pesticide manufacturing facility in Barcelona, Spain during the summer of 1984 contained phosmet concns of 5-10 ppm .

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