Ames Mutagenicity of Tap Water III. Analysis of Mutagenicity Level of Tap Water in Japan

Quantitative Evaluation of the Genotoxic Activity of Japanese Tap Water Using the Umu Test

“…Though the genotoxicity seemed to have a tendency to increase with the TOC value, it was shown that the GA could not be calculated from the corresponding TOC value even if the data was considered by each group of the raw water. The previous investigation also reported the same finding (Urano et al, 1995). However, it was shown that 84% of the measured data was within 50% of the least-squares fit, regardless of the type of the raw water (JWWA, 2004).…”

“…(1) can be transformed as follows: (2) is a converted value from the genotoxicity of tap water to 4NQO. The VSD 4NQO was estimated as 0.86 ng/kg/d based on previous reports (Ando, 1981;Urano et al, 1995) and according to assumption i) (Bercu et al, 2010). The GA values, corresponding to the 10 -5 level of carcinogenic risk, could then be roughly estimated using Eq.…”

“…The assay was not carried out with the S9 mix because it had been reported that the genotoxicity tested by the Ames assay with the S9 mix was much weaker than without the S9 mix (Urano et al, 1995). A summary of the procedure for the umu test is as follows.…”

“…Because there have been no reports on the quantitative genotoxicity of tap water nationwide using the standardized umu test, a previous report using the Ames test by Urano et al (1995) was used for comparison. Results of the Ames test cannot be compared directly with the results of the umu test because of the differences in their mechanisms, although both of them are able to detect genotoxicity.…”

“…As for the genotoxicity of tap water, Urano et al (1995) performed the Ames mutagenicity test, which is one of the typical genotoxicity tests along with the umu test, for Japanese tap water samples concentrated using a solid-phase extraction method, and they reported results ranging from less than 470 to 9,200 net rev./L. Since then, however, there have been few reports on how the genotoxicity of tap water has changed, and no investigations have reported the occurrence of genotoxicity nationwide using the standardized umu test.…”