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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 64% in 28 days (ISO 10708)

Key value for chemical safety assessment

Additional information

No experimental data evaluating the potential for ready biodegradability of isooctadecanoic acid, mono- and diester with glycerol (CAS No. 97358-80-0) are available. Therefore, a ready biodegradability study from an analogue category member, castor oil hydrogenated (CAS No. 8001-78-3) is used as read-across in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Both substances are esters formed from the combination of C18 fatty acids and glycerol as alcohol component. Castor oil hydrogenated is predominantly a triglyceride (>80%, the three hydroxyl functional groups of the glycerol molecule are esterified with fatty acids) whereas the target substance contains mainly mono and diesters (triester < 10%). Considering this fact and that the C-chain length of the main fatty acid component for both subtances is C18, a higher degree of biodegradation might be expected for isooctadecanoic acid, mono- and diester with glycerol and read-across from castor oil hydrogenated would be a worst-case and therefore, justified.

One study evaluating the potential for ready biodegradability of castor oil hydrogenated (CAS No. 8001-78-3) is available (Richterich and Mühlberg, 2001). The test was conducted according to the ISO 10708. Activated sludge was exposed for 28 days to the test and biodegradation followed by measuring O2 consumption in the test vessels. After 28 days, the test substance reached 64% biodegradation. As the substance is an UVCB substance and thus, formed by constituents with different degrees of esterification, sequential (instead of concurrent) biodegradation is expected to take place. Thus, referring to Annex I to 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 criterion can be disregarded in this case and the substance considered as readily biodegradable.

 

Based on the results obtained for the structurally similar analogue substance (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5) isooctadecanoic acid, mono- and diester with glycerol can be considered readily biodegradable.