Suppression of mutation induction and failure to detect mutagenic activity with athabasca tar sand fractions

5 different histidine-requiring strains of Salmonella typhimurium were used to test the mutagenic activity of 7 different fractions of Athabasca tar-sand. None of the 7 fractions (bitumen, maltenes, asphaltenes, saturated, monoaromatic, diaromatic and polyaromatic hydrocarbons), showed positive mutagenic response in any of the Salmonella typhimurium strains. We have tested a wide range of concentrations. The results obtained so far are consistent with the lack of mutagenic activity of all investigated fractions in the absence and in the presence of metabolic activation. Assuming that there might be an association between the absence of mutagenic activity and the complexity of the tar-sand fractions, we investigated the effect of the polyaromatic hydrocaron fraction on the mutagenicity of the carcinogenic agent 2-aminoanthracene. The data obtained indicate clearly that the polyaromatic hydrocarbon fraction suppresses the mutagenic activity of 2-aminoanthracene.