Validation of a method to measure bioaccumulation in terrestrial organisms by means of an international ring test

The aim of the project was the validation of a bioaccumulation test with terrestrial organisms (soil dwelling oligochaetes) by an international ring test. The test method was developed taking into account existing methods (UBA-reports 206 03 909 (1997) and 298 64 416 (2001)). A test protocol was prepared and used to run the test. A total of 14 institutions (governmental, universities, contract laboratories and industry) from 7 different countries participated in the ring test. Lumbricids (Eisenia fetida, E. andrei) and enchytraeids (Enchytraeus albidus, E. crypticus) were used as test species. The test compounds were ¹⁴C-labelled hexachlorobenzene (HCB) and cadmium chloride. The ring test runs were performed once by each laboratory, and consisted of an uptake and an elimination phase. Analysis of total radioactive residues and cadmium concentrations in soil and tissue samples was performed. In total, 33 tests were performed and evaluated. Several courses and workshops were organised to inform and train the participants. 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 programme.