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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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In accordance with Column 2 of REACH Annex IX, the simulation test on ultimate degradation in surface water and the sediment simulation test do not need to be conducted as the substance is readily biodegradable. Identification of degradation products is also not necessary.

The registration substance is a substance of unknown or variable composition (UVCB). Its constituents' structures incorporate an alcohol functional group on an alkyl chain, with carbon numbers in the range (C14-C20, predominantly C16-C18). The alkyl structures are predominantly monobranched (methyl or ethyl branching, at or beyond the 6 carbon position) and may be considered ‘essentially linear. Therefore, available data for linear constituents (C14 – C18) are presented as supporting data.

The degradation of C14 linear alcohol in sediments was determined in two studies conducted in accordance with OECD 314 test method and using radiolabelled (14C) test substance. After 92 days, 76.5% mineralisation to CO2 was obtained using sediment from Ohio River near Cincinnati, Ohio area (Federle T Wand Itrich N R, 2010a). After 149 days, 83.6% mineralisation to CO2 was obtained using Lytle Creek sediments from Wilmington, Ohio (Federle T W and Itrich N R, 2010b).

The degradation of C18 linear alcohol in sediments was determined in a similar study, conducted in accordance with OECD 314 test method and using radiolabelled (14C) test substance (Itrich, 2010). After 60 days, 61.1% mineralisation to CO2 was obtained using sediment from Ohio River, and 71.6% mineralisation to CO2 after 60 days was obtained using Great Miami River sediments.

These three sediment degradation studies indicatedthat there are two pools of substance, understood to represent the strength of adsorption of the alcohol to sediment particles, which degrade at different rates.

In another study, using activated sludge and radiolabelled (14C) test substance, 76.7% mineralisation of C14 to CO2 after 48 h was determined in accordance with OECD 314B (Federle, 2005). In the same study, 66.3% mineralisation of C16 to CO2 after 48h was determined. Another OECD 314 test using activated sludge and using radiolabelled (14C) test substance, indicates 95% mineralisation of C16 to CO2 in 31 days (Federle, 1993).