Evaluation of methods for predicting the toxicity of polycyclic aromatic hydrocarbon mixtures

Risk assessments of polycyclic aromatic hydrocarbon mixtures are hindered b y a lack of reliable information on the potency of both mixtures and their individual components. This paper examines methods for approximating the to xicity of polycyclic aromatic hydrocarbon (PAH) mixtures. PAHs were isolate d from a coal tar and then separated by ring number using HPLC. Five fracti ons (A-E)were generated, each possessing a unique composition and expected potency. The toxicity of each fraction was measured in the Salmonella/mutag enicity assay and the Chick Embryo Screening Test (CHEST). Their abilities to induce ethoxyresorufin-O-deethylase and to inhibit gap junction intercel lular communication in rat liver Clone 9 cells were also measured. In the S almonella/mutagenicity assay, fractions were predicted to have potencies in the order C > D > E > B > A. Toxic equivalency factors (TEFs) for fraction s A-E were in the order E greater than or equal to D > C > B > A. TEF value s were 20 652, 20 929, 441, 306, and 74.1 mug of BaP equiv/g, respectively. A lack of agreement between assay-predicted potencies and chemical analysi s-predicted potencies was observed with other assays and other methods of c alculation. The results demonstrate the limitations of using a single metho d to predict the toxicity of a complex PAH mixture.