The existing toxicity data on the effects of polycyclic aromatic hydrocarbons (PAHs) on Pseudokirchneriella subcapitata (green alga) are quite insufficient. These data were derived using different test techniques (e.g. conventional batch test, closed-system test, semi-static test). The relative toxicity relationship for various PAHs is thus difficult to interpret. Consequently, the current toxicity database is insufficient and also inadequate for analyses of the effects of PAHs on P. subcapitata. This study evaluated the toxicity of eleven PAHs using an air-tight test technique. The relative toxicity relationship was determined on a uniform basis, and was different from the relationship based on current available data. P. subcapitata. was found to be more susceptible to PAHs than Daphnia magna, fathead minnow, and Scenedesmus subspicatus. Quantitative structure-activity relationship (QSAR) was established based on the chemical's hydrophobicity with R2 equal to 0.88. Photo-induced toxicity for various PAHs was also explored by exposing PAHs under UV-photoactivation. Toxicity of anthracene, benzanthrone, and benzo[a]anthracene was found to increase 3.5 to 25 times after UV exposure. Phototoxicity was observed when the HOMO-LUMO gap varied between 6.8 and 8.0 eV.

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