Recommendations for advancing test protocols examining the photo-induced toxicity of petroleum and polycyclic aromatic compounds

Abstract

Photo-induced toxicity of petroleum products and polycyclic aromatic compounds (PACs) is the enhanced toxicity caused by their interaction with ultraviolet radiation and occurs by two distinct mechanisms: photosensitization and photomodification. Laboratory approaches for designing, conducting, and reporting of photo-induced toxicity studies are reviewed and recommended to enhance the original Chemical Response to Oil Spills: Ecological Research Forum (CROSERF) protocols which did not address photo-induced toxicity. Guidance is provided on conducting photo-induced toxicity tests, including test species, endpoints, experimental design and dosing, light sources, irradiance measurement, chemical characterization, and data reporting. Because of distinct mechanisms, aspects of photosensitization (change in compound energy state) and photomodification (change in compound structure) are addressed separately, and practical applications in laboratory and field studies and advances in predictive modeling are discussed. One goal for developing standardized testing protocols is to support lab-to-field extrapolations, which in the case of petroleum substances often requires a modeling framework to account for differential physicochemical properties of the constituents. Recommendations are provided to promote greater standardization of laboratory studies on photo-induced toxicity, thus facilitating comparisons across studies and generating data needed to improve models used in oil spill science.

Fig. 1.

Conceptual diagram of photo-induced toxicity mechanisms using the polycyclic aromatic compound (PAC) anthracene as the example petroleum compound. Photosensitization (top) occurs separate from the organism, and photomodification (bottom) occurs within the organism.

Fig. 2.

General time sequence of the development and evolution of predictive phototoxicity models (Aeppli et al., 2012; Dutta and Harayama, 2000; Grote et al., 2005; Krylov et al., 1997; Larson et al., 1979; Mekenyan et al., 1994; Newsted and Giesy, 1987; Oris and Giesy, 1985; Veith et al., 1995).

Fig. 3.

General sequence of light and oil exposure in photosensitization (left) and photomodification (right) experiments.

Fig. 4.

Phototoxicity decision framework for photosensitization and photomodification experiments with petroleum substances and polycyclic aromatic compounds (PACs).