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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Ready biodegradability: Apparently low and limited by the rate of hydrolysis and/or bioavailability. There is evidence that a degree of biodegradation does occur and modelling of possible biodegradation pathways indicate that aerobic degradation is likely, the first steps in this being hydrolysis to trimellitic acid and 2 -ethylhexanol, both of which have been shown to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

In reported tests of both ready biodegradability and inherent biodegradability in water, the substance was considered to have relatively low biodegradability. This issue has been investigated further with additional biodegradation studies in which (prolonged) Closed Bottle tests were performed according to slightly modified OECD Test Guidelines. The tests were modified to permit measurements after 28 days as prolongation (enhanced biodegradability testing) may be used as an indicator of the non-persistence of a substance. None of the results obtained demonstrate ready biodegradability. Best results were obtained when the test substance was administered with Agnique (a non biodegradable alkylphenol alkoxylate) or in an emulsion of silicone oil and Agnique. The somewhat higher degree of biodegradation observed in tests with a lower initial test substance concentration of 1.0 mg/L indicates limited bioavailability. It is possible that the rate of biodegradation may be limited by the rate of hydrolysis of the test substance and/or the rate with which the substance dissolves. Modelling of possible biodegradation pathways indicate that aerobic degradation is likely, the first steps in this being hydrolysis to trimellitic acid and 2-ethylhexanol, both of which have been shown to be readily biodegradable.