Validation of a sediment bioaccumulation test with endobenthic aquatic oligochaetes by an international ring test

The aim of the project was the validation of a sediment bioaccumulation test with endobenthic oligochaetes by an international ring test. The test method was developed taking into account existing methods (UBA-reports 298 67 419 (1999) and 206 03 106/03 (1999)). A test protocol was prepared and used to run the test. A total of six institutions (universities, contract laboratories and industry) from four different countries participated in the ring test. Lumbriculus variegatus and Tubifex tubifex were used as test species. The test compound was ¹⁴C-labelled hexachlorobenzene (HCB). The ring test runs were performed once by each laboratory, and consisted of a 28-d uptake phase, and a 10-d elimination phase. Analysis of total radioactive residues in water, sediment, and tissue samples was performed by the performing laboratories. In total, seven valid tests were performed and evaluated. Several courses and workshops were organised to inform and train the participants. A key aspect of the project was the detailed statistical evaluation of the test results. In a first step following practical ring-testing, the kinetic results of the single test runs were evaluated by nonlinear regression analysis. Additionally, comparability and variability of the results, as well as advantages and difficulties of the method were assessed and discussed by the ring test participants at a workshop. The outcome of the workshop was used to refine evaluation of the results and the test methodology, to define the most appropriate endpoints, the prerequisites for establishing a suitable test design and the validity criteria of this test. As a major outcome of the ring test, the draft test guideline, which closely follows formal requirements of the OECD test guidelines, was updated and prepared for submission to OECD’s Test Guideline Program.