Registration Dossier

Environmental fate & pathways

Phototransformation in air

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Administrative data

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Description of key information

Photochemical degradation rates: (all  x10-12 cm3/(molecule.s):
3.2 (average of 10 measured, with OH radicals)
3.1 (calc, OH)
Predicted half life: 36-40 hours in the atmosphere (reaction with OH radicals
Degradation in presence of NO2: Half life =11.5hours @100ppmNO2. 20-30% degradation after 5 hours @1ppm.
Degradation in presence of SO2 significantly slower than with NO2.

Key value for chemical safety assessment

Half-life in air:
38 h

Additional information

If ethanol is present in ambient air, it is expected to exist almost entirely in the vapour phase, based on the physicochemical properties cited in this dossier. This substance is not expected to absorb UV light in the environmentally significant range of >290 nm and is not therefore expected to undergo direct photolysis on sunlit soil surfaces, in the atmosphere or in aquatic environments. However, experimental data backed up by modelling predicts that it is likely to undergo indirect photolysis through hydroxyl radical reaction at a slow to moderate rate, with an estimated half life of 36 -40 hours at an OH concentration of 1.56million OH/cm3 and a 12 hour day). A figure of 38 hours is used for the key parameter. Data also indicates that reaction with NOx as a sensitiser can be significant, depending on the concentration present, but levels are unlikely to be high enough to be of impact.

Available data indicates that the most labile site for degradation is predominantly the methylene carbon. The main breakdown products identified are acetaldehyde and 2,3 -dihydroxybutane.