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Environmental fate & pathways

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Administrative data

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Additional information

From the data available for the two constituents it can be concluded that the reaction mass will be readily biodegradable, will be no subject of hydrolytic degradation, has a low log Kow (and thus low bioaccumulation potential) and low adsorption potential to organic material.

Ethanol:

If ethanol is present in ambient air, it is expected to exist almost entirely in the vapour phase, based on the physicochemical properties. 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 was 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 (log Pow), the substance has a low potential for bioaccumulation.

Distribution modelling suggests that environmental concentrations of ethanol are likely to be very low. Based on emissions modelled using a typical use pattern and default emission factors either from the EU TGD or derived by expert assessment, regional water concentrations are predicted to be less than 5ug/l and air concentrations less than 0.3ppb. This appears to be supported by measurements of ambient ethanol and methanol in the atmosphere at a remote location in Alaska, which found average levels of around 1.0ug/m3 (0.5ppb). However, since the authors of the study felt that the source of the methanol/ethanol was more likely to be of biological origin rather than man-made and the age of the study (1960s), this may be simply a co-incidence rather than a mutually supportive finding. Samples of water from a highly polluted river in Japan taken around 1980 were found to contain between 2 and 4ppm of ethanol. Because this data is quite old, it is unclear if it has any relevance to current levels of ethanol in the aquatic environment.

Isopropanol:

The substance is considered to be readily biodegradable, and possesses a low octanol-water partition coefficient (log Pow3) that leads to a prediction of very high mobility in soil, and also to a low potential for bioaccumulation.

The substance is not expected to persist in the environment.