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Augmenting aquatic species sensitivity distributions with interspecies toxicity estimation models
Citation:
Awkerman, J., Sandy Raimondo, CrystalR Jackson, AND M. Barron. Augmenting aquatic species sensitivity distributions with interspecies toxicity estimation models. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 33(3):688-695, (2014).
Impact/Purpose:
Statistical analyses and multimodel comparison evaluate the effect of inclusion of extrapolated values in SSD. Sensitivity analyses address the relative impact of estimation error for toxicity values in hazard concentration estimation.
Description:
Species sensitivity distributions (SSD) are cumulative distribution functions of species toxicity values. The SSD approach is increasingly being used in ecological risk assessment, but is often limited by available toxicity data necessary for diverse species representation. In this study we augment aquatic species SSDs with predicted toxicity values using interspecies correlation estimation (ICE) models and then determine the uncertainty in the hazard concentration at the 5th percentile (HC5). When SSDs had similar species composition, the proportion of HC5s developed with ICE extrapolated toxicity values within 5-fold of the HC5s of reference SSDs (all measured values) increased from 0.67 (random species assemblage) to 0.94 (same species composition). Variance in toxicity values among represented species was also dependent on the mode of action of a chemical. HC5 estimations for acetylcholinesterase inhibitors showed the greatest discrepancies from reference HC5 when SSDs were limited to only commonly tested species. The results of this study indicate that ICE models used to augment SSDs do not greatly affect HC5 uncertainty when extrapolation error was distinguished from the influence of species composition. Uncertainty analysis of risk assessments using SSD hazard concentrations should address the species composition especially for chemicals with widely varying toxicological effects.
