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Environmental fate & pathways

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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 half life. Ethanol is considered resistant to hydrolysis but since it is readily biodegradable, no further testing is required. There is no data available on phototransformation in water or soil.

The biodegradation of ethanol was assessed at a number of concentrations using a non-adapted domestic sewage innoculum in a freshwater medium using a 20 day study. Rapid degradation was observed. In a study that used a method based on a proposed improvement to a Sturm guideline study to make it more suitable for volatile substances, ethanol was shown to be readily biodegradable. In both cases, degradation well in excess of 60% was seen with 5 days. Based on the results of these studies, ethanol meets the criteria to be classified as readily biodegradable. The biodegradation of ethanol in artificial salt water was also assessed with a non-adapted domestic sewage innoculum.. Degradation was observed to a level of 75% over 20 days and 68% in 10 days. This results shows it meets the requirement for designation as readily biodegradable in sea water. In a study to assess the biodegradability of ethanol under anaerobic conditions, ethanol was exposed to methanogenic bacteria derived from an aquifer slurry. Degradation was followed by measuring the pressure increase through emissions of CH4 and CO2 and, at the end of the study, by GC analysis to quantify the amount of methane produced. After a lag time of 25 -30 days, methane emissions equivalent to 91% mineralisation were eventually seen (after an unquantified time) indicating biodegradability under anaerobic conditions. Testing for degradation in sediment and soil is not required because the substance is found to be readily biodegradable in screening tests. Degradation in soil and sediment can confidently be expected.

Based on its low partion co-efficient (logkoW), the substance has a low potential for bioaccumulation.