Interactive Effects of Mixtures of Phototoxic PAHs.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment as components in complex mixtures derived from petroleum based products. PAHs are unique in their ability to absorb UV light, resulting in significant increases in acute toxicity. The objective of this study was to determine if mixtures of the phototoxic PAHs fluoranthene, pyrene, and anthracene conform to the additive model of toxicity. Median lethal concentrations (LC50) were calculated for mysid shrimp (Americamysis bahia) and inland silverside (Menidia beryllina) exposed to individual, binary, and ternary mixtures of the selected PAHs. Mixtures were evaluated on a toxic unit basis to account for potency differences and toxicity data was analyzed using the concentration-addition and independent-action models. Data indicated that the model of additivity is sufficient in describing the toxicity of mixtures of phototoxic PAHs; therefore predictive models should consider an additivity model for assessing the toxicity of hydrocarbon mixtures.