Predicting petroleum phototoxicity

Phototoxicity to Daphnia magna was studied on 14 polycyclic aromatic hydrocarbons (PAHs) and 22 petroleum products (ranging from diesel to crude oil). The phototoxicity ranking of pure PAHs was about the same as found in another study on fish gill cells in vitro (Toxicology 127 (1998) 143), suggesting that the relative acute phototoxicity does not differ significantly between different species. Most petroleum products were found to be phototoxic, although the results differ somewhat between test methods (preparation of water-accommodated fractions or petroleum ether dissolved oil slurries). The degree of phototoxicity of a sample is related to both the source and the refining process of the crude oil. The best chemical predictors found were the concentrations of eight phototoxic parent PAHs. An even simpler analytical technique suggested for initial screening would be direct measurements of “total PAH,” where samples having more than 3% PAH should be studied further.