Abstract
In order to reduce the mutagenicity of tap water, it is important to investigate the level of mutagenic precursor contained in the tap water source. The Mutagen Formation Potential (MFP) on chlorination is the index of the content of the precursor in water. We measured the MFP of Shinano River downstream water which is used as a tap water source at many points, to evaluate the environmental safety. The measurement was conducted at 6 points from January 2002 to December 2002, monthly by Ames assay usingS. typhimuriumstrain TA100 without S9 mix. The MFP values tended to be higher in winter than in other seasons. On the other hand, only a slight difference was observed among the annual means of the 6 points. The means of MFP at each point ranged from 600 to 1, 000 net rev./l and it was suggested that the mutagenic risk level of Shinano River water was relatively low. We also measured the mutagenicity of 6 tap water samples in the region. Annual means of mutagenicity for each tap water sample ranged from 500 to 990 net rev./l. The values tended to be higher in winter, as was the case with the MFP values.
