Ames mutagenicity and concentration of the strong mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone and of its geometric isomer E-2-chloro-3-(dichloromethyl)-4-oxo-butenoic acid in chlorine-treated tap waters.

The Ames mutagenicity and the concentration of the strong Ames mutagen 3-chloro-4-(dichloro-methyl)-5-hydroxy-2(5H)-furanone (MX) and its geometric isomer E-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (E-MX), derived from chlorination of humus, were determined in XAD extracts of tap water collected from 26 localities in Finland. The 23 tap waters treated with disinfectants gave a positive response in strain TA100. MX and E-MX were detected in all extracts exhibiting mutagenicity with the exception of 3 extracts of marginal activity. MX accounted for 15-57% (average 33%) of the observed mutagenicity. The concentration of E-MX was slightly lower than the corresponding concentration of MX. Linear correlations were observed between mutagenicity and concentration of MX and E-MX, with correlation coefficients of 0.894 for MX and 0.910 for E-MX.