Mel and I have another paper with co-authors in a forthcoming issue of the SETAC journal Integrated Environmental Assessment & Management. This one is on the use of Multi-criteria Decision Analysis (MCDA) for choosing between different test designs when performing fish full life cycle (FFLC) tests with potential endocrine active substances. FFLC tests are increasingly required in the ecotoxicological assessment of endocrine active substances. However, they have not been internationally standardized or validated, and it is currently unclear how such tests should best be designed to provide statistically sound and ecologically relevant results.
Using the logical framework of MCDA, a comparative evaluation of FFLC test endpoints for assessing endocrine-active substances was conducted. The analysis was performed by three workshop groups with expertise in environmental regulation, statistics, fish ecology and aquatic toxicity testing. Each workgroup focused on one of three species: fathead minnow (Pimephales promelas), Japanese medaka (Oryzias latipes) and zebrafish (Danio rerio).
Test endpoints (e.g. fecundity, growth, gonadal histopathology) were scored for each species for various desirable features such as statistical power and ecological relevance, with the importance of these features determined by assigning weights to them.
The endpoint F1 fertilization success consistently emerged as a preferred option for all species. In addition, some endpoints scored highly in specific species, such as development of secondary sexual characteristics (fathead minnow) and sex ratio (zebrafish). Other endpoints such as hatching success ranked relatively highly and should be considered as useful endpoints to measure in tests with any of the fish species.
MCDA also indicated relatively less preferred endpoints in fish life cycle tests. For example, intensive histopathology consistently ranked low, as did measurement of diagnostic biomarkers, such as vitellogenin, most likely due to the high costs of these methods and their limited ecological relevance.
Life cycle tests typically do not focus on identifying toxic modes/mechanisms of action, but rather, single chemical concentration-response relationships for endpoints (e.g. survival, growth, reproduction) that can be translated into evaluation of risk. It is therefore likely to be an inefficient use of limited resources to measure these mechanism-specific endpoints in life cycle tests, unless the value of such endpoints for answering particular questions justifies their integration in specific case studies.