Detection and quantification of DNA strand breaks in human cells induced by contaminants in Japanese tap waters

FADU (Fluorometric Analysis of DNA Unwinding) is one of the most simple and sensitive methods to detect DNA strand breaks. We modified the original FADU protocol in this study, and tried to apply the method as a short-term test to detect DNA-damaging environmental agents, using an SV40- transformed human fibroblast cell line WI38-VA13. DNA strand breaks induced by physical and chemical carcinogens such as γ-rays, ultraviolet light, MNNG, 4NQO, B(a)P were detected efficiently by using the modified protocol. We also tried to detect DNA strand breaks caused by tap waters. Tap water samples were concentrated using the Sep-pak C18 and DNA strand breaks induced in human cells were measured by FADU assay. The tap water samples of Osaka City induced a dose dependent increase in DNA starnd breaks in human cells. But this DNA toxicity was reduced by rat liver S9 fraction, glutathione and water boiling.