Mutagen X and chlorinated tap water are recombinagenic in yeast

This study determines the effects of a water disinfection by-product, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (also known as mutagen X or MX) and chlorinated tap water on genomic instability in the yeast Saccharomyces cerevisiae. Tap water samples collected from Cherepovets (Russia) and Boston (MA, USA), were extracted using XAD absorption and ethyl acetate elution. MX and these water extracts were then tested for their ability to induce intrachromosomal recombination (deletions or DEL events), interchromosomal recombination (ICR) and aneuploidy (ANEU) using the yeast DEL assay. MX strongly induced DEL, ICR and ANEU events with a positive dose response and no threshold. Cherepovets tap water induced DEL and ICR events while evidence of ANEU induction was weak. The DEL induction potencies were stronger at higher concentrations. The estimated contribution of MX to DEL induction varied from over 50% at low concentrations (which is comparable to a typical contribution of MX to Ames mutagenicity of tap water) to between 2 and 10% at highest concentrations. For Boston tap water, there was only weak evidence of DEL induction and no evidence of ICR and ANEU induction. This is consistent with the results of other studies, which reported much higher concentrations of MX and stronger Ames mutagenicity in Cherepovets tap water than in Boston tap water.