Ryota OHASHI

Safety evaluation of river waters throughout Japan and a groundwater by mutagen formation potential

Toshiya KOMATSU, Shuji HIMENO and Shoichi FUJITA


River water is mainly used as a source for drinking water in Japan. Because mutagens are contained in drinking water, it is important to investigate the level of mutagenic precursor contained in river water. In this study, we measured the mutagen formation potential (MFP) of river water in 19 rivers throughout Japan using Ames mutagenicity assay, to investigate the level of mutagen precursor contained. The MFP level of river waters was generally highest in the condition of Salmonella typhimurium strain TA100 without S9 mix, which shows direct mutagens causing base-pair substitutions are mainly produced by chlorination. The MFP values ranged from 210 to 9010 net rev. / L, which shows that the values have much differences between samples. MFP values of 13 % samples exceeded 3000 net rev. / L, the value which is proposed as a guideline of mutagenicity in drinking water. In general, MFP of the rivers located in big cities had higher values. We also measured the MFP of a groundwater that is used as drinking water source in Nagaoka-city. Since the MFP level of the groundwater was very low (80 net rev. / L), mutagenic risk level of the groundwater was quite low.