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Environmental fate & pathways

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A range of OECD environmental fate studies assessing the biodegradation of Fatty acids, C12-18 and C18-unsatd., 2-sulfoethyl esters, sodium salts (CAS Number:85408-62-4) in aerobic and anaerobic media have been conducted. The registered substance is a multi constituent substance, with four main constituents >10%: C12, C14, C16 and C18 fatty acid isethionates (C12= 26%, C14= 14%, C16=28%, C18= 23%). In addition, the registered substance that is commercially available contains <10% (minor constituents) C8 and C10 fatty acid isethionates, and unreacted impurities including free Sodium Isethionate (SI), free fatty acids and sodium vinyl sulphonate.

Screening studies, assessing the evolution of CO2from the test systems were conducted using the test material and SLI(76), where SLI(76) has the fatty acids stripped from the commercial mixture.Biodegradation of the test material was shown to be rapid under aerobic (301B) and anaerobic (ISO 11734, 1995) conditions. Unilever_Ready biodegradation_BD-RS43 -01 (1983) demonstrated that DEFI is readily biodegradable with ≥77.8% degradation within 28 days and the 10 day-window was met following OECD 301B.

A number of simulation studies measuring the primary degradation [14C-radiolabelled] of the shortest (Lauryl, C12) and the longest (Stearyl, C18) chained fatty acid isethionates have been conducted. The biodegradation of Lauryl and stearyl isethionate in river water (OECD 314d) was shown to be extremely rapid with degradation half life <4 hours (Unilever_River die-away_KDE100028, 2010). The partitioning and biodegradation of C12 and C18 fatty acid isethionates in activated sludge systems was estimated in an OECD 303A study (Unilever_CAS Study_ECS090080, 2010). Extensive primary biodegradation of both short and long chained isethionates was observed (99.8%), partitioning to sludge was minimal (0.16%) and the percentage remaining in effluent was 0.05%.

Due to the very low weighted average log Kow (1.65) the test material has a very low potential for bioaccumulation. The average measured log Koc for C12 sodium isethionate was 3.16 showing moderate partitioning to organic matter (Unilever_Adsorption/desorption_KAS090058, 2009).