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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Fatty Acid Glycerides are readily biodegradable.

Key value for chemical safety assessment

Additional information

Six studies investigating the ready biodegradability of Fatty Acid Glycerides are available (CAS No. 8001-78-3, 67701-33-1, 73398-61-5, 91744-20-6, 97722-02-6) and one anaerobic study (CAS No. 31566-31-1). The tested substance concentrations range from 2 to 100 mg/L.

Twice a Closed Bottle Test (similar to OECD guideline 301D) was conducted using domestic sewage as inoculum and test substance concentrations of 2 and 5 mg/L. These tests show the ready biodegradability of the tested substances. A CO2 Evolution test according to OECD 301B comes to the same result, using domestic activated sludge as inoculum and test substance concentrations of 10 mg/L. As well a Manometric Respirometry Test according to OECD guideline 301F using activated sludge as inoculum and test substance concentrations of 100 mg/L determined ready biodegradability of the tested substance. Furthermore two BODIS Tests according to ISO 10708 (designed in particular for poorly water-soluble compounds) were conducted with activated sludge as inoculum. One test with 37 mg/L test substance concentration shows ready biodegradability with 93% biodegradation within 28 days. The second BODIS Test with 100 mg/L (Castor oil, hydrogenated, CAS No. 8001-78-3, castor oil, hydrogenated) shows a degradation of 64%. However despite being biodegraded in excess of 60% after 28 days (64%), the test did not meet the "14-day window" criteria. As the substance is an UVCB substance and thus consist of constituents with different chain-lengths, sequential (instead of concurrent) biodegradation takes 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 14-day window should not be considered for this UVCB substance and due to a degradation of > 60% within 28 days Castor oil, hydrogenated can be regarded as readily biodegradable. This assumption is confirmed by QSAR calculations for the hydrogenated castor oil coming to the result that the substance is also readily biodegradable (see category justification). This is consistent with the other available biodegradation tests and thus, QSAR calculations (see category justification) and experimental results come to the conclusion that all Phase-1-category members of Fatty Acid Glycerides are readily biodegradable according to OECD criteria.