MP6 Quantitative Structure Activity Relationships (QSARs)
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall

(DIM-1117-799315) Acute Aquatic Toxicity and Species Extrapolation Models.

Mekenyan, Ovanes¹, Dimitrov, Sabcho¹, Koleva, Yana¹, Schultz, T², ¹ Laboratory of Mathematical Chemistry, Bourgas University “Assen Zlatarov”, Bourgas, Bulgaria² Department of Comparative Medicine, College of Veterinary Medicine, The University of Tennessee, P. O. Box 1071, Knoxville, Ten, USA

ABSTRACT- This investigation examines the quantitative structure-activity relationships for aquatic toxic potency of variety chemicals with different mechanisms of toxic action, such as non-polar narcotics, esters and amine narcotics, phenols, anilines, aldehides, etc. The models proposed here are based on the comparative study of ciliate (Tetrahymena pyriformis) population growth impairment data, fish (Pimephales promelas, Poecilia reticulate, Carassius auratus) mortality data, crustacean (Daphnia magna) efficient (48h immobilisation) and mortality data, tadpole (Rana temporaria) minimum narcosis concentration, mosquito larvae (Culex tarsalis) mortality data, as well as data for other aquatic animals. The modeling method for explaining toxicity of non-polar narcotcs is based on the response-surface concept, using bioconcentration (log BCF) and orbital electrophilicity (E_LUMO) as global molecular descriptors for accumulation and reactivity of chemicals, respectively. For covalently acting chemicals the global electrophilicity is replaced by local molecular descriptors assessing reactivity of toxicophores. The statistical quality of the derived interspecies models was found to be comparable with those of QSARs fitted on separate endpoints. The interspecies models are easy to interpret and provide a method for the extrapolation of toxic potency from one organism to another.

Key words: ciliate, fathead minnow, acute toxicity, interspecies QSAR