Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

If released to air, acetonitrile is expected to exist solely as a vapor in the ambient atmosphere based on a moderately high vapor pressure. Vapor-phase acetonitrile will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals. The half-life of this reaction is estimated to be on the order of weeks to months. Wet deposition may reduce atmospheric acetonitrile.

Acetonitrile is expected to persist for months in the troposphere. Acetonitrile is not expected to to be susceptible to direct photolysis.

If released to soil, acetonitrile is expected to have high mobility. Volatilization from moist and dry soil surfaces is expected.

Aerobic biodegradation is expected to be the major loss process in soil and water. In the 2000 EU Risk Assessment of acetonitrile, the Competent Authority concluded that acetonitrile should be considered as ready biodegradable for local scenarios if WWTP is available, while, due to the higher uncertainty and the application of the Precautionary Principle, the rate constants reported in the TGD for inherent biodegradable chemicals must be applied for regional/continental scenarios and to derive the rate constant for soil.

If released to water acetonitrile is not expected to adsorb to suspended solids and sediment. Volatilization from water surfaces is expected to be an important fate process. The potential for acetonitrile to bioaccumulate in aquatic organisms is low. Hydrolysis is not expected to be an important fate process.

Level III fugacity modeling of acetonitrile distribution, using the US EPA EPIWIN software predicted the following percent distribution and half-lives for acetonitrile in environmental media:

Air - 13%, 1544 hours

Water - 44.1%, 360 hours

Soil - 42.8%, 720 hours

Sediment - 0.0811%, 3240 hours