The presence of KCl in the exposure medium strongly influences the mutagenicity of metabolites of polycyclic aromatic hydrocarbons in Escherichia coli.

Previous studies demonstrated that the ion composition of the exposure medium may strongly influence the mutagenicity of many compounds in the liquid preincubation modification of the reversion assay with his- Salmonella typhimurium strains. Similar influences were now observed in the reversion assay with trp- Escherichia coli strain WP2 uvrA. The exposure medium was 8 mM sodium phosphate buffer (pH 7.