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Environmental fate & pathways

Adsorption / desorption

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Description of key information

A high log Koc for Fatty acids, C18-unsaturated, dimers, hydrogenated (CAS No. 68783-41-5) is expected: log Koc > 5.

Key value for chemical safety assessment

Additional information

Because the substance is a composition of different homologues, the Koc values of well-defined representative structures were calculated with EPISUITE (KOCWIN v2.00) (Bucior, 2012a, b, c) and a weight of evidence approach is applied.

The main factor determining the log Koc value of fatty acids is the carbon chain length. For monomers (C18), the calculated log Koc values are between 3.7 (octamethyldecanoic acid, MCI method) and 4.7 (octadecanoic acid, Kow method). It can be concluded that the overall contribution of monomers fulfills the condition: 4 < log Koc (monomers) < 5. The calculated results for dimeric constituents (C36) are considerably higher: log Koc from ca. 7.4 (Kow method) to ca. 9.1 (MCI method). As the main fraction represented in the substance is the dimeric fraction, it is concluded that for Fatty acids, C18 unsaturated, dimers, hydrogenated (CAS 68783-41-5) adsorption to organic carbon in soils and sediments is to be expected. Log Koc is very high: log Koc > 5.

No additional tests on adsorption/desorption are to be conducted. The result is used for the chemical safety assessment.