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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: More than 60% were degraded within 28 days (80%). As the substance is a racemic mixture, the 10 -day window does not apply.

 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

While the substance proved to be readily biodegradable in an OCED 301 F Manometric Respiratory Test, it proved to be not readily biodegradable in an OECD 301 D Closed Bottle Test. Both studies are guideline-conform and considered as valid.

According to ECHA "Guidance on information requirements and chemical safety assessment - Chapter R.7b: Endpoint specific guidance (November 2012)", p179, "Realising that ready biodegradability tests may sometime fail because of the stringent test conditions, in general, and the differences among the individual tests in terms of their stringency, consistent positive test results from test(s) should generally supersede negative test results. However, when conflicting test results are reported, it is recommended to consider such differences in stringency and to check the origin of the inoculum in order to check whether or not differences in the adaptation of the inoculum may be the reason (OECD, 2006)."

Based on this it is allowed to use the outcome from the manometric respirometry study for characterisation of the biodegradability of the test item (key study). Following reliability criteria (according to the guidance) however still have to be double checked in the study report for the manometric respirometry test: (1) test material concentration within in applicable range, (2) possible inoculum pre-treatment, and (3) potential inconsistencies in ThOD computation for the test material. No inconsistencies which might have affected the reliability of the study were found in the study report.

Based on these reasons it is proposed that the outcome from the manometric respirometry study outweighs the outcome from the closed bottle test. In the chemical safety assessment and the environmental exposure assessment, the substance will be considered as readily biodegradable. In consequence the substance can be considered as fulfilling the "not (v)P" criterion for vPvB and PBT assessment.