Azinphosmethyl

Azinphosmethyl's production may result in its release to the environment through various waste streams; its use as an insecticide will result in its direct release to the environment. If released to air, a vapor pressure of 2.0X10-7 mm Hg at 25 deg C indicates azinphosmethyl will exist in both the vapor and particulate phases in the atmosphere. Vapor-phase azinphosmethyl will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 2.5 hours. Particulate-phase azinphosmethyl will be removed from the atmosphere by wet or dry deposition. Azinphosmethyl contains chromophores that absorb at wavelengths >290 nm and, therefore, may be susceptible to direct photolysis by sunlight. If released to soil, azinphosmethyl is expected to have moderate to slight mobility based upon a Koc range of 298 to 4644. Volatilization from moist soil surfaces is not expected to be an important fate process based upon an estimated Henry's Law constant of 2.9X10-9 atm-cu m/mole. Half-lives of 5.3 to 40 days have been reported in soil under field conditions. If released into water, azinphosmethyl is expected to adsorb to suspended solids and sediment based upon the Koc values. A decrease from 99 mg/L to 49 mg/L after 4 days incubation in a stirred flask containing azinphosmethyl as the sole carbon source and a mixed culture indicates that biodegradation in water may be an important environmental fate process. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant. An estimated BCF of 30 suggests the potential for bioconcentration in aquatic organisms is moderate. Hydrolysis half-lives for azinphosmethyl in water at pH 8.6 were 36.4, 27.9, and 7.2 days at 6, 25, and 40 deg C, respectively. The half-life of azinphosmethyl in seawater was 11 days when exposed to natural sunlight, while the half-life in river water was 8 days when exposed to natural sunlight. Occupational exposure to azinphosmethyl may occur through inhalation and dermal contact with this compound at workplaces where azinphosmethyl is produced or used. Monitoring data indicate that the general population may be exposed to azinphosmethyl mainly via ingestion of food. (SRC)