AhR-mediated activities of polycyclic aromatic compound (PAC) mixtures are predictable by the concept of...

Risk assessments of polycyclic aromatic hydrocarbons (PAHs) are complicated because these compounds exist in the environment as complex mixtures of hundreds of individual PAHs and other related polycyclic aromatic compounds (PACs). In this study, the hypothesis that concentration addition (CA) can be used to predict the aryl hydrocarbon receptor (AhR)-mediated activity of PACs in mixtures containing various combinations of PACs was tested. AhR-mediated activities of 18 mixtures composed of two to 23 PACs, which included PAHs, azaarenes and oxygenated PAHs, were examined by the use of the AhR-based H4IIE-luc bioassay. Since greater AhR-mediated activities have been observed in soils contaminated by PAHs, investigations were done to test whether soil extract matrix or the presence of non-effect PACs might affect responses of the H4IIE-luc bioassay. Our results showed that AhR-mediated activities of mixtures of PACs could be predicted by the use of concentration addition. Additive activities of PACs in multi component mixtures along with the insignificant effect of the soil matrix support the use of concentration addition in mass balance calculations and AhR-based bioassays in risk assessment of environmental samples. However, independent action (IA) could not be used to predict the activity of mixtures of PACs.