Identification of a new mutagenic polychlorinated biphenyl derivative in the Waka River, Wakayama, Japan, showing activation of an aryl hydrocarbon receptor-dependent transcription.

Water samples from the Waka River, which runs through an area housing many chemical industry facilities in Wakayama, Japan, have been found to show significant mutagenicity, especially without a mammalian metabolic activation system (S9 mix) in the Salmonella typhimurium YG1024 strain. Mutagens in the river water were adsorbed to 3 kg of blue cotton, extracted with methanol/ammonia, and separated by several low- and high-pressure liquid chromatography steps with reversed-phase columns. One mutagen (0.6 mg), accounting for 50% of the total mutagenicity of the adsorbed materials, was isolated. On the basis of the mass, high-resolution mass, (1)H NMR and (13)C NMR spectra, the chemical was determined to have a polychlorinated biphenyl skeleton with nitro and amino substitution groups. Well-designed chemical synthesis of the putative mutagen revealed it to be 4-amino-3,3'-dichloro-5,4'-dinitrobiphenyl. This novel compound exerted strong mutagenicity without the S9 mix, inducing 66,000 and 140,000 revertants/nmol in S. typhimurium TA98 and YG1024, respectively. Moreover, this polychlorinated biphenyl derivative was proven to activate the human aryl hydrocarbon receptor-mediated transcription in a lac Z reporter gene assay with an efficiency almost the same as that of beta-naphthoflavone, well-known to be a synthetic aryl hydrocarbon receptor agonist. It is possible that the mutagen is formed unintentionally via postemission modification of drainage water containing parent chemicals, such as 3,3'-dichlorobenzidine or 3,3'-dichloro-4,4'-dinitrobiphenyl, which are known to be raw materials in the manufacture of polymers and dye intermediates in chemical plants.