PARENT SESSION

1F - QSAR
Poster Hall
8:30 AM - Tuesday, 29 April 2003
Chair: Schüürmann, G.¹, ¹
Co-chair: Verhaar, H.J.M.², Cronin, M.³, ^{2 3}

(TUP/46) A QSAR for the Photoinduced Toxicity of PAHs to Lemna gibba is Predictive for Daphnia magna.

Lampi, Mark¹, Huang, Xiao-Dong¹, El-Alawi, Yousef¹, Dixon, D.¹, Greenberg, Bruce¹, ¹ University of Waterloo, Waterloo, Ontario, Canada

ABSTRACT- Solar radiation is known to enhance the toxicity of PAHs through photosensitization and photomodification mechanisms. The photosensitized production of highly reactive singlet oxygen has been widely studied as a major mechanism of photoinduced toxicity. PAH photomodification, generally through photooxidation, results in a wide array of products, many of which are more toxic than the parent compound. This is known to occur at environmentally relevant levels of solar radiation in aquatic systems. Previously, we have developed a model to predict the photoinduced toxicity of PAHs in the aquatic macrophyte Lemna gibba based on 16 PAHs. This QSAR model showed that a photosensitization factor (PSF) and a photomodification factor (PMF) could be additively combined to accurately describe photoinduced toxicity. This model was subsequently found to correlate very well with the toxicity to the marine bacterium Vibrio fischeri. To further validate this model, it was necessary to determine whether it is predictive in other organisms of ecotoxicological importance. Daphnia magna was chosen as the next model organism. Toxicity was assessed as immobility of D. magna neonates after 48h exposure to individual PAHs, and presented as EC50s. All assays were performed under simulated solar radiation (SSR). As with both L. gibba and V. fischeri, neither the PSF nor the PMF demonstrated great correlation to toxicity to D. magna individually. However, the sum of these factors resulted in a strong correlation to toxicity. This data provides further evidence that this model, which was developed based on the assumption of a bipartite mechanism of PAH photoinduced toxicity, is applicable across a broad range of species of interest.

Key words: PAHs, photoinduced toxicity, QSAR, Daphnia magna