Organisation and performance of an international ringtest for the validation of the enchytraeid reproduction test
An enchytraeid reproduction test ring test was performed in line with OECD requirements. Twenty-nine institutions (mainly universities and contract research laboratories) from 15 countries from Europe and North America participated in this ring test. The co-ordinating laboratory centrally distributed the test chemicals, guidance papers and test organisms to all participants. In addition, several training courses were organised. Most participants performed two tests with the fungicide carbendazim and two tests with 4-nitrophenol. For each substance, the first test was designed according to an ECx approach and the second according to a NOEC approach. A total of 92 tests were performed. About 72% of these tests were valid. A major aspect of the project was the detailed statistical evaluation of the test results, leading to recommendations for an optimised ecotoxicological test design. The effects of the two test chemicals on enchytraeid reproduction were in the range expected from data in the literature on oligochaete toxicity. However, due tof a high variability in the number of juveniles statistical evaluation of the data was sometimes difficult. This variability was caused by several reasons including hormesis effects and the lack of experience of some participants. Comparison of the data from the NOEC and ECx approaches pointed to a clear advantage of the latter (EC10 values always seemed to be lower than NOEC values determined in the same test). As a result of the ring test, the enchytraeid reproduction test draft guideline was significantly improved. The new guideline version was standardised by OECD, ISO and ASTM in 2004.