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Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 78% biodegradation in 28 days (ISO Draft BODIS test)
69-95% in 28 days (OECD 301D)

Key value for chemical safety assessment

Additional information

No experimental data evaluating the biodegradation potential of Glycerides, C16-18 mono-, di- and tri- (CAS No. 91052-54-9) are available. Therefore, biodegradation data from structurally related category members, docosanoic acid, ester with 1,2,3-propanetriol (CAS No. 77538-19-3) and Glycerides, C14-18 mono- and di- (CAS No. 67701-33-1) are used as read-across (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5). All three substances are esters formed from the combination of long-chain fatty acids (C16-C18, CAS No. 91052-54-9 and CAS No. 67701-33-1, and C20-24, CAS No. 77538-19-3) and glycerol, containing similar amounts of mono, di and triglycerides. As biodegradation tends to increase at decreasing C-chain lengths, reading across from docosanoic acid, ester with 1,2,3-propanetriol (CAS No. 77538-19-3) represents a worst-case scenario for the target substance and therefore it is justified.

A study evaluating the potential for ready biodegradability of Glycerides, C14-18 mono- and di- (CAS No. 67701-33-1) is available (Richterich, 1991). This test was conducted according to a method equivalent to OECD Guideline 301D, under GLP conditions. Activated sludge was exposed to the test substance for 28 days at 20°C, and biodegradation measured by O2 consumption. After 28 days, the test substance reached 95% (2 mg/L test concentration) and 69% (5 mg/L test concentration) biodegradation. Therefore, Glycerides, C14-18 mono- and di- is readily biodegradable. On the other hand, one study evaluating the potential for ready biodegradability of docosanoic acid, ester with 1,2,3-propanetriol (CAS No. 77538-19-3) is available (Richterich and Mühlberg, 2001). The test was conducted according to ISO Draft BOD Test for Insoluble Substances, under GLP conditions. 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 78% biodegradation. As the substance is an UVCB substance and thus consists of 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 related category members (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5), Glycerides, C16-18 mono-, di- and tri- (CAS No. 91052-54-9) can be regarded as readily biodegradable.