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PM10 Assessing Toxicology: Critical Body Residue Approach
(PM167) Application of the Narcosis Target Lipid Model to Predict Toxicity of Algal Species and Development of HC5s.
McGrath, J1, Parkerton, T2, Di Toro, D1, 3, 1 HydroQual, Mahwah, NJ, USA2 ExxonMobil Biomedical Sciences, Annandale, NJ, USA3 University of Delaware, Newark, DE
ABSTRACT- The narcosis target lipid model was developed to predict the toxicity of chemicals that act via narcosis to aquatic organisms. The model accounts for variations in toxicity due to species sensitivities and chemical differences. The model is based on the hypothesis that lipid is the site of action within the organism. Previous work has focused on the application of this model to fish and invertebrates. The first objective of this study was to determine if this model could logically be extended to predict toxicity endpoints for algal species. Toxicity data were gathered for algal species where the toxicity testing was conducted in closed systems to prevent loss of volatile compounds. The slopes of the individual log(EC50)-log(Kow) relationships were found to be not statistically different from the universal narcosis slope derived from the earlier analysis of toxicity data for non-algal species. The universal narcosis slope was applied to the individual data sets and critical body burdens were determined for each algal species. These were then compared to the critical body burdens of the aquatic species in the original work. No difference in sensitivity was found. The target lipid model parameters were then used as input into a statistical extrapolation procedure that accounts for variability in critical body burdens and acute to chronic ratios to compute HC5 values. Resulting HC5 values were compared to various guidelines for protection of aquatic species. The benefits of using mode of action-based statistical extrapolation procedures for deriving environmental quality objectives will be highlighted.
Key words: toxicity, algal , narcosis, HC5
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