EVALUATION OF MODELS FOR PREDICTING THE PHOTOTOXIC POTENCY OF POLYCYCLIC AROMATIC-HYDROCARBONS

The objective of this study was to evaluate the validity of two previo usly developed models to predict: (a) the relative phototoxic potency of polycyclic aromatic hydrocarbons (PAHs) through structure activity relationships (SARs), and (b) the interactive effects of variable ligh t intensity and PAH dose on phototoxicity. The oligochaete Lumbriculus variegatus was exposed to multiple concentrations of the PAHs anthrac ene, pyrene, fluorene and fluoranthene for 96 h, followed by a 96 h ho lding period in clean water at three different ultraviolet (UV) light intensities. Based upon measured tissue residue concentrations, anthra cene and pyrene were approximately equitoxic, and both were four-fold more potent than fluoranthene. Fluorene was not phototoxic to the olig ochaete. These results were in good quantitative agreement with the to xicity predictions of the SAR model. Time-dependent lethality of the t hree phototoxic PAHs to the oligochaete was accurately modeled by plot ting mortality as a function of the product of initial tissue residue of the PAH and UV light intensity to which the organisms were exposed, which also was in good agreement with the interactive toxicity model. These studies contribute to the technical basis for developing an int egrated modeling approach to predicting the ecological risk of mixture s of phototoxic PAHs.