Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Propylene oxide reacts with hydroxyl radicals in the atmosphere. The rate of this reaction has been determined by a number of investigators. As a reasonable worst-case the longest half-life, 32 days (EU RAR, 2002), will be used in the assessment.

Several studies are available on the hydrolysis of propylene oxide. Meylan et al. (1986) determined hydrolysis kinetics of propylene oxide based on various experimentally determined values.At 25°C the calculated half-life of propylene oxide is 12.9 days in freshwater and 2.4 days in seawater . Due to a specific reaction with chloride ions, the hydrolysis rate in seawater is higher.

Propylene oxide was found ready biodegradable (89% after 28 days) under aerobic conditions in a modified MITI test (MITI 1988). Propylene oxide is not readily biodegradable under the stringent conditions of a closed bottle biodegradation test (Shell Research Ltd., 1985).The available studies indicate that in general propylene oxide can assumed to be ready biodegradable, but under certain stringent conditions this may not be the case.

Due to the fact that the substance is considered ready biodegradable, no significant concentrations are present in the water, sediment and soil compartments. This is supported by exposure assessment with EUSES. The maximal local PEC value that was calculated was 2.31.10-3mg/L for freshwater, 8.65.10-4mg/L for seawater, 2.37.10-3mg/kg (w. w.) for the freshwater sediment, 8.87.10-4mg/kg (w. w.) for marine sediment and 0.0013 mg/kg (w. w.) for the soil compartment. Since these concentrations are very low, no significant exposure of the water, sediment and soil compartment is assumed and therefore simulation tests are not needed.

In accordance with column 2 of REACH Annex IX, the bioaccumulation test on fish does not need to be conducted as the substance has a low potential for bioaccumulation (log Kow < 3).

In accordance with column 2 of REACH Annex VIII, the adsorption test does not need to be conducted as the substance has a low potential for adsorption (log Kow < 3).