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(25-03) QSARs for the Photoinduced Toxicity of PAHs to Bacteria and Plants Require Factors for Photosensitization and Photomodification. El-Alawi, Yousef*,1, Huang, Xiao-Dong1, Dixon, George1, Greenberg, Bruce1, 1 Dept. of Biology, University of Waterloo, Waterloo, Ontario, Canada ABSTRACT- Many studies have proved that natural sunlight greatly enhances the toxicity of PAHs. Photosensitization reactions (e.g., generation of singlet-state oxygen) and photomodification reactions (e.g., photooxidation of PAHs to more toxic species) are both pathways of photoinduced toxicity of PAHs in aquatic environments. The principles of quantitative structure-activity relationships (QSARs) were applied to PAHs showing that a photosensitization factor (PSF) and photomodification factor (PMF) both can be additively combined to describe photoinduced toxicity. This QSAR model was based on the photoinduced toxicity of 16 PAHs to the duckweed Lemna gibba. The next objective was to apply the QSAR model developed for L. gibba to another organism. The organism chosen was the luminescent marine bacteria Vibrio fischeri. Toxicity data for the QSAR model was inhibition of luminescence and inhibition of growth to V. fischeri by sixteen PAHs. The PMFs for the PAHs from the L. gibba QSAR showed a moderate correlation to bacterial toxicity, where as the PSFs showed only a weak correlation to toxicity. As was the case for L. gibba, summing the PMF and the PSF resulted in a strong correlation to toxicity that had predictive value. Thus, a QSAR model derived for plants accurately described the phototoxicity of PAHs to a bacterial species. This indicates that the bipartite mechanism of PAH photoinduced toxicity should be broadly applicable. Key words: QSAR, Polycyclic Aromatic Hydrocarbons, Vibrio fischeri, Lemna gibba |
