a b s t r a c t a r t i c l e i n f oPolycyclic Aromatic Hydrocarbons (PAHs) constitute a family of over one hundred compounds and can generally be found in complex mixtures. PAHs metabolites cause DNA damage which can lead to the development of carcinogenesis. Toxicity assessment of PAH complex mixtures is currently expressed in terms of toxic equivalents, based on Toxicity Equivalent Factors (TEFs). However, the definition of new TEFs for a large number of PAH could overcome some limitations of the current method and improve cancer risk assessment. The current investigation aimed at deriving the relative potency factors of PAHs, based on their genotoxic effect measured in vitro and analyzed with mathematical models. For this purpose, we used a new genotoxic assay (γH2AX) with two human cell lines (HepG2 and LS-174T) to analyze the genotoxic properties of 13 selected PAHs at low doses after 24 h treatment. The dose-response for genotoxic effects was modeled with a Hill model; equivalency between PAHs at low dose was assessed by applying constraints to the model parameters. In the two cell lines tested, we observed a clear dose-response for genotoxic effects for 11 tested compounds. LS-174T was on average ten times more sensitive than HepG2 towards PAHs regarding genotoxicity. We developed new TEFs, which we named Genotoxic Equivalent Factor (GEF). Calculated GEF for the tested PAHs were generally higher than the TEF usually used. Our study proposed a new in vitro based method for the establishment of relevant TEFs for PAHs to improve cancer risk assessment.
An analysis of the ir spectra of HF–H2O mixtures containing from 10 to 97% of HF has been used to determine the evolution of the ionic species of HF. The results indicate that water and the ions H3O+F−, H3O+, and F− are present in the solutions containing less than 46% w/w of HF. In the solutions containing at least 50% w/w of HF, bands characteristic of the ion HF2− start appearing and their intensity increases with the concentration of HF, up to a concentration of 90%. As well, polymers of (HF)n have been detected in the solutions containing the highest concentration of HF. These results can be used to explain the electrochemical behaviour of solutions of HF–H2O.
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