11/06/2015

Available test systems for the determination of biodegradation – Identification of gaps in the persistency evaluation

German Federal Environment Agency, Project No. 54429, project duration 05/2015 – 03/2016

Sponsor:

German Federal Environment Agency (Project No. 54429)

Realisation:

FoBiG GmbH, Markus Schwarz, Klaus Schneider (project management)

Hydrotox GmbH, Stefan Gartiser

ECT Oekotoxikologie GmbH, Flörsheim, Thomas Junker

Project duration:

05/2015 – 03/2016

Summary:

Data on biodegradability and persistence are, inter alia, required for the identification of persistent, bioaccumulative and toxic substances (PBTs) and very persistent and very bioaccumulative substances (vPvB substances) according to REACH Annex XIII. Results from ready biodegradability screening tests (e.g. OECD 301 A-F, OECD 310) allow a first estimate on potential persistency. However, only "readily biodegradable" substances are assumed as being "non-persistent". For the tests on inherent degradability (OECD 302 B and C) very strict criteria are used, which exclude them mainly from persistency evaluation in practice. Simulation tests (e.g. OECD 308, OECD 309) are considered as “gold standard" in persistency evaluation. These are performed with radiolabeled substances under more realistic conditions, but are much more complex and therefore more expensive. To reduce these costs so-called "enhanced screening tests" were proposed, which have an intermediate position between tests for ready biodegradability and the simulation tests and are intended to be exclusively used for persistency evaluation. The improvements proposed consist, inter alia, in an increase in the biomass and of the volume of the vessels as well as an extension of the test period to, for e.g. 60 days. However, no guidance on the borderlines to be set for "enhanced screening tests" exists.

A literature study was performed to review the applicability of established and new biodegradability tests for assessing persistence in the frame of PBT/vPvB assessments under REACH. Screening tests for ready and inherent biodegradability, proposals for enhanced ready tests as well as newly designed compartment-specific screening tests were analysed for strengths and weaknesses and proposals are made how to improve their performance and suitability for assessments of persistence. Although not in the focus of this study, some recommendations are also given for simulation tests (OECD 307, 308, 309) in the context of evaluating persistence. Recommendations focus on defining, standardising and optimising test conditions, on validity criteria and interpretation of test results. In the case of enhanced screening tests it is critically discussed which test modifications could be introduced without challenging the screening nature of the tests. Furthermore, specific issues such as non-extractable residues (NER) in tests with soil and sediment and substances difficult to test in standard tests (poorly water soluble, highly volatile or UVCB substances) are addressed.

The literature study has been published in the UBA-Texte series No. 10/2017.

Contact person at Hydrotox GmbH
Dr. Stefan Gartiser, E-Mail: gartiser(at)hydrotox.de, Tel: +49-(0)761-45512-24

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