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4C - Combined effects of contaminants and environmental stressors (MOP/183) Photo-enhanced algal toxicity by PAHs. Altenburger, Rolf 1, Brack, Werner 1, Grote, Matthias1, Walter, Helge1, Schüürmann, Gerrit1, 1 UFZ Centre for Environmental Research, Leipzig, Germany, Germany ABSTRACT- PAH toxicity is typically assessed in terms of discriminating between compounds elucidating specific or unspecific effects in biosystems. While for Ah-receptor mediated specific effects abundant information is present and even understanding of structural prerequisites is available, many PAHs do not affect biosystems via induction of their own metabolism. To assume in consequence that the majority of PAH compounds in the environment merely act by an unspecific, narcotic mode of action is rather speculative. Using a cellular algal bioassay we were able to demonstrate that lipophilicity and thus unspecific toxicity could explain observable PAH toxicity of 13 selected compounds only for conditions were no UV light was present before or during the biotest. With illumination of the samples using simulated sunlight, a compound-specific enhancement of toxicity of one and more orders of magnitude was observed. For the case of anthracene it could be shown using effect-oriented identification technique that the effective compounds were photomodified metabolites. Mixture experimentation can be shown to provide information regarding the mode of joint action. The relevance of structural properties to explain these findings will be reflected. Key words: mode of action, phototoxicity, joint action, algal bioassay |
