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Environmental fate & pathways

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

Two studies investigating the ready biodegradability of 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) are available. The key study was 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 test substance is assumed not to be inhibitory to activated sludge microorganisms based on a biodegradation of > 25% in the toxicity control after 14 d.

The second study was rated reliability 3 “not reliable” based on inconsistent results (Fletcher, 1997). This study was performed according to OECD 301B under GLP conditions using secondary effluent from an activated sludge plant as inoculum. The results cannot be used for the assessment since the observed biodegradation values showed a very high variability on each sampling day (95% confidence limit: 14.9 - 70.8).

In conclusion 2-octyldodecyl isooctadecanoate is considered readily biodegradable according to the OECD criteria.