IDENTIFICATION OF OXIDIZED AND REDUCED FORMS OF THE STRONG BACTERIAL MUTAGEN (Z)-2-CHLORO-3-(DICHLOROMETHYL)-4-OXOBUTENOIC ACID (MX) IN EXTRACTS OF CHLORINE-TREATED WATER

Oxidized and reduced forms of (Z)-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (MX) and the oxidized form of its geometric isomer (EMX) were synthesized, evaluated for mutagenic potency in the Ames assay, and quantitatively determined in chlorinated aqueous solutions of fulvic acids, in chlorinated natural humic water, and in chlorinated drinking water. The compounds were found in chlorinated drinking waters at concentrations equal to or greater than MX. In the Ames assay the pure oxidized compounds were nonmutagenic at the dose levels tested while the reduced form of MX was weakly mutagenic relative to MX. These findings suggest that the cis arrangement of the dichloromethyl and chlorine groups around the carbon-carbon double bond and the presence of the aldehyde function strongly enhance the mutagenic response.