Chemical Fact Sheet

Chemical Abstract Number (CAS #) 297972
CASRN 297-97-2
Phosphorothioic acid, O,O-diethyl O-pyrazinyl ester
Analytical Methods EPA Method 622.1
EPA Method 8141
Molecular FormulaC8H13N2O3PS

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

Use FORMERLY A SOIL INSECTICIDE ON VEGETABLES; CORN; STRAWBERRIES; MINT /Former uses/: Thionazin is a soil insecticide and nematocide effective against a number of plant parasitic as well as free living nematodes, including those attacking buds, bulbs, leaves and roots, as well as against soil dwelling pests such as root maggots and symphylids and foliar insects such as aphids and leaf miners. When incorporated in mushroom compost at spawning it is effective against mushroom flies.
Boiling Point 80 DEG C
Melting Point -1.7 DEG C
Molecular Weight 248.26
Density 1.204-1.210 @ 25 DEG C
Environmental Impact If produced thionazin may enter the environment as a fugitive emission during its manufacture, formulation, and during its application as a pesticide. If released to the atmosphere, it is expected to exist predominantly in the vapor phase. Rapid destruction by the reaction with photochemically produced hydroxyl radicals is expected to occur; the half-life for this process can be estimated at 4.3 hr. Wet deposition may also occur. If released to soil, limited data suggests that microbial degradation under aerobic conditions may occur. The half-life of 10-100 ppm thionazin in soil is on the order of 2-6 weeks which encompasses the removal processes leaching, biodegradation and hydrolysis. Higher concentrations of thionazin are removed at a slower rate. It appears to be removed more rapidly from alkaline soils than from acidic soils. Thionazin is expected to be highly mobile in soil. If released to water, thionazin is expected to undergo hydrolysis at an experimentally determined half-life at 25 deg C of about 30 days at pH 7. Neither adsorption to sediment and suspended matter, nor bioconcentration in fish and aquatic organisms are expected to be significant fate processes. Occupational exposure to thionazin may occur by inhalation or dermal contact for those involved in the synthesis, formulation, or application of this pesticide.
Environmental Fate TERRESTRIAL FATE: SOIL WAS TREATED WITH ZINOPHOS SHORTLY AFTER PLANTING. DETECTABLE AMT REMAINED FOR 1 YR IN CHURCH FIELD SOIL (PH 5.4) BUT IN HIGH FIELD (PH 7.3) NO RESIDUES DETECTED AFTER THIS PERIOD. ZINOPHOS HALF-LIFE IN SOILS VARIED FROM ABOUT 5-12 DAYS @ LOW DOSAGE (5 PPM) TO ABOUT 9-22 DAYS @ HIGH DOSAGE (20 PPM). TERRESTRIAL FATE: Thionazin was described as slightly persistent in soil, with a given half-life of 2-6 weeks encompassing removal by leaching, hydrolysis, and biodegradation . Commercial formulations of 10 ppm thionazin applied to the top or broadcast 4 inches into a sandy loam soil (pH= 6.1) resulted in a removal half-life of 23 days . The initial loss rate when thionazin was applied at 250 ppm was much slower, and traces of thionazin remained after 2 years . In a laboratory assay, 100 ppm thionazin lost 95% of its biological activity in 100 days . Thionazin was found in soil up to one year after its application to an acidic sandy loam field, but this compound was not detected after 10 weeks in alkaline clay soil . AQUATIC FATE: If released to water, thionazin is expected to undergo hydrolysis. An experimentally determined half-life for the hydrolysis of thionazin at 25 deg C under neutal conditions was given as 29 days at pH 7(1,2). A half-life of approximately 40 and 4 days at pH 10 and pH 11, respectively, can be calculated from a basic hydrolysis rate constant of 7.3 L/mole-hr(1,2). Thionazin was reported as having a half-life of 14 weeks in natural water at pH 6.8 . ATMOSPHERIC FATE: If released to the atmosphere, the vapor pressure, 3X10-3 mm Hg at 30 deg C , suggests that thionazin may exist entirely in the vapor phase in the ambient atmosphere . Thionazin is expected to undergo rapid destruction by the gas phase reaction with photochemically produced hydroxyl radicals; the half-life for the reaction can be estimated at 4.3 hr(2,SRC). The water solubility, 1140 mg/l at 25 deg C , suggests that wet deposition may occur.

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