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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

2,6-Xylidine is not readily biodegradable. If the inoculum is adapted to the test substance and after a prolonged contact time, biodegradation occurs.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

For assessing biodegradability of 2,6-Xylidine a weight-of-evidence approach was applied. Different tests according to OECD TG 301F and 302B were performed by BASF (1993 & 1994) using non-adapted as well as adapted inoculum, partly mixed from different sources. When non-adapted inoculum is used, no biodegradation can be observed in a test according to OECD TG 301F after 28 days of exposure. A Zahn-Wellens test according to OECD TG 302B also using non-adapted inoculum indicates 2,6 -Xylidine to be partly eliminated from water (45% after 28 days, DOC removal). When adapted inoculum from a finished biodegradation study with the same test substance is used within a test system according to OECD 301F degradation rates increase significantly. After 28 days the degradation rates between the two test vessels using 2,6-Xylidine as test substance show a certain variation (17% and 56% degradation, related to the BOD/ThOD). After a prolonged test duration of 52 days both batches show degradation rates between 65% and 76% related to the BOD/ThOD. Beside biotic degradation, abiotic loss via evaporation from the water surface is found to be an important fate path as indicated in another test according to OECD TG 302B (BASF 1993).

Overall it can be stated that 2,6-Xylidine is biodegradable after adaption of the inoculum.