The Mutagenicity of PAHs in Binary Mixtures

Melissa Stafford and Dr. Robin Autenrieth

            Risk Assessment of toxic environmental samples is difficult due to the complexity of chemicals in mixtures.  The quantifications of mixtures has several components that generate considerable uncertainty.  Upper bound limits, paucity of toxicity data concerning specific chemicals and mixtures of those chemicals, and additive assumptions are a few of those.  The common procedure for evaluating complex mixtures of unknown parts is the addition of solo toxicity data based on concentration of the chief carcinogens.  Although this procedure gives a good rough estimate of total toxicity, this practice has components absent that could be necessary to understanding the carcinogenic action of the whole mixture.  Complex mixtures of carcinogens often express such complex behaviors as synergism and antagonism.  In these experiments we looked closely at the action of Polycyclic Aromatic Hydrocarbons in binary mixtures using the Ames assay.  In specific we titrated BaP (Benzo-a-Pyrene) into Chrysene and 5-MethylChrysene (5-MeCh) and then preformed an inverse procedure in order to indicate interaction propensity.  The results suggest that, although the assumption of additively was not violated, there may be an inhibitory effect between closely related carcinogens.  It is theorized that the inhibitory effects are likely the result of either changes in solubility or competition for metabolic activation/ receptor binding sites.  In the next step, Gap Junction Intercellular Communication assays will be run to further classify the interactions in these same mixtures of compounds and to better understand the effects of complex mixtures on human health and the environment.

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