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Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 68.1 - 71.7% (CO2 evolution) after 28 d (OECD 301B)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no studies investigating the ready biodegradability of fatty acids, C16-18, 2-octyldodecyl esters (CAS 96690-38-9) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to the structurally related category member 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) was conducted. The read-across substance is representative to evaluate the biodegradation of fatty acids, C16-18, 2-octyldodecyl esters. 2-octyldodecyl isooctadecanoate is characterized by a similar (longer) fatty acid chain length (C18iso compared to C16-C18) and the same fatty alcohol component (2-octyldodecanol). The study with the read-across substance 2-octyldodecyl isooctadecanoatewas performed according to OECD 301B under aerobic conditions using domestic activated sludge as inoculum (Desmares-Koopmans, 1998). A test substance concentration of approx. 14.5 mg/L was degraded to an extent of 68.1 - 71.7% after 28 d. Since 2-octyldodecyl isooctadecanoate is a UVCB substance and consists of structurally similar constituents with [e.g. different chain-lengths, degree and/or site of branching or stereo-isomers], sequential (instead of concurrent) biodegradation of the individual structures can take place, but all can be considered as readily biodegradable. Thus, referring to Annex I of the OECD Guideline for Testing of Chemicals ‘Revised introduction to the OECD guidelines for testing of chemicals, section 3’ (OECD, March 2006), the 10-day window should not be considered for this UVCB substance and due to a degradation of >60 % within 28 days the substance can be regarded as readily biodegradable. Moreover, the read-across substance is assumed not to be inhibitory to activated sludge microorganisms based on a biodegradation of > 25% in the toxicity control after 14 d.

Based on the results from one structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) it can be concluded that fatty acids, C16-18, 2-octyldodecyl esters is readily biodegradable according to the OECD criteria.