Emi OKUDA

Evaluation of Road Runoff by Ames Mutagenicity Assay

Toshiya KOMATSU, Shuji HIMENO, Shoichi FUJITA

It is known that various toxic substances are included in the road runoff of heavy traffic roads. Because some substances show mutagenicity, it is important to evaluate the mutagenicity level in road runoff from a viewpoint of influence to the river ecosystem. Ames mutagenicity assay was conducted in this study using actual road runoff from a heavy traffic national road. The mutagenicity level in the road runoff was highest in the condition of S. typhimurium strain TA100 with S9 mix, which shows indirect mutagens causing base-pair substitutions are mainly involved. No correlation was found between mutagenicity and DOC, SS or the rainfall. The mutagenicity level of TA100+S9 was relatively high and increased in the latter period of the rain. It was suggested that the mutagenicity level still increases if the no rainfall period (about 2.5 days in this test period) extends. Mutagen formation potential (MFP) on chlorination of the road runoff was also evaluated by Ames assay, to investigate the level of mutagen precursors from a viewpoint of utilization as drinking water source. In the case of MFP, the mutagenicity level was highest in the condition of S. typhimurium strain TA100 without S9 mix.