MUTAGENICITY TEST OF GAMMA-IRRADIATED HUMUS IN AQUEOUS-SOLUTION FOR THE SAFETY EVALUATION OF IRRADIATED WATER

Fulvic acid and humic acid which are difficult to be removed from water by ordinary purification processes were degraded by **6**0Co gamma-irradiation and the partially degraded samples were examined for the mutagenetic activity using Salmonella mutagenicity test. No mutagenic activity was detected in 1000-fold concentrated samples. Addition of S9 mix did not stimulate mutagenicity either. These results revealed that **6**0Co gamma irradiation did not produce mutagenetic substances from the partially degraded fulvic and humic acids at detectable quantities.