Further development of screening tests for the evaluation of potential PBT substances

German Federal Environment Agency, FKZ 3718 65 410 0, project duration 09/2018 - 09/2021


German Federal Environment Agency (FKZ 3718 65 410 0)


Hydrotox GmbH, Stefan Gartiser (Project management)

ECT Oekotoxikologie GmbH, Thomas Junker

Project duration:

2019 - 2021


Screening tests of the OECD 301 series and the OECD 310 are used for testing of ready biodegradability and for the identification of persistent, bioaccumulating and toxic substances (PBT substances). Although these tests differ considerably in methodology and historical background, the test results are considered as equivalent. One goal of the project is to provide recommendations for further development and standardization of these tests in order to improve the comparability of the test results. Screening tests are considered stringent, but are based on very artificial test conditions. Therefore, only a positive result can be used to relieve a persistence suspicion. A negative result requires the application of OECD simulation tests, which allow the derivation of degradation half-lives and are carried out with more realistic substance and inoculum concentrations. However, these tests usually require the use of 14C-labeled test substances and are much more time and cost-intensive compared to screening tests. The project aims at contributing to close the existing gap between screening tests and complex studies through so-called "enhanced ready" tests.

In WP 1 (work package 1), a systematic comparison of the established test guidelines for determining ready biodegradability will be carried out while examining options for their harmonisation. For this purpose, in particular the experiences of the performing laboratories will be queried. The results will be presented and discussed in 2019 at an international one-day workshop at the Federal Environment Agency.

In WP 2, potential test substances intended for the practical investigations in AP 3 will be researched, which will be carried out to verify the conclusions on the persistence assessment. In particular, substances with an expected biodegradability of 20-40% or substances with low water solubility for which valid simulation studies are available should be included.

In AP 3, practical laboratory tests will be carried out with five substances selected in AP 2 in order to test the influence of the changed test conditions in "enhanced ready" tests. This includes in particular an extension of the test duration, the enlargement of the test vessels and the use of alternative inoculums. In addition, so-called combination tests with parallel determination of several endpoints (O2 consumption and CO2 development) will be carried out. In total, about 20 tests are scheduled.

In AP 4, proposals for the development of a test guideline for "enhanced ready biodegradation tests" will be developed.

In AP 5, the impact of the project results for the persistence assessment under REACH will be analyzed.

Contact person at Hydrotox GmbH

Dr. Stefan Gartiser

gartiser(at)hydrotox.de, Tel: +49-(0)761-45512-24