Report published on further development of screening tests for the evaluation of potential PBT substances

Different ready biodegradability tests (OECD 301 series and OECD 310) are currently used for evaluating if a substance is readily biodegradable and for identifying potentially persistent substances. Although the methods differ considerably, the test results are considered equivalent. In persistency assessments under REACH, enhanced ready biodegradability tests with an extended test duration (up to 60 days) and an increased test vessel size can be performed in cases where, based on ready biodegradability test results, a substance cannot be classified as non-persistent under environmental conditions. However, only few data from such enhanced tests are available and neither guidance on the design and interpretation, nor suitable validity criteria have been established so far.

In the present report, recommendations are given for further development and standardisation of screening tests for the evaluation of potential PBT substances in order to improve comparability of the test results. Additional knowledge is generated regarding the application of enhanced ready biodegradability tests.

A survey was performed among European laboratories to identify their experiences with ready biodegradability testing. The results were discussed during an international workshop in April 2019. Laboratory experiments were performed for five test substances to verify the impact of enhancements (an extended test duration and an increased test vessel size) on the results of ready biodegradability tests. The use of final effluent from a sewage treatment plant as an alternative inoculum was investigated, and tests with parallel determination of different endpoints (O₂ consumption, CO₂ evolution, DOC removal) were performed. The testing experience led to suggestions regarding the test design, the evaluation and the interpretation of enhanced ready biodegradability tests, which can be used as a starting point for further guidance. The impact of the proposed recommendations for the persistence assessment under REACH is discussed.

For further information, see the project report:

Gartiser, S., Brunswik-Titze, A., Flach, F., Junker, T. (2023). Further development of screening tests for the evaluation of potential PBT substances. UBA-Texte 10/2023.

For additional information on the project, see here.

Detailed information on the practical testing is provided in the following publication:

Gartiser, S., Brunswik-Titze, A., Flach, F., Junker, T., Sättler, D., Jöhncke, U. (2022). Enhanced ready biodegradability screening tests for the evaluation of potential PBT substances. Science of the Total Environment 833:155134.