MUTAGENICITIES OF BANGKOK AND TOKYO RIVER WATERS

Samples of water from the Chao Phraya river and some connected canals in Bangkok, Thailand, and from the Sumida and Ara rivers in Tokyo, Jap an, were tested for mutagenicity using blue rayon to adsorb the mutage ns. The samples from the Chao Phraya river and connected canals at sit es located 50-150 km from the river mouth taken in May 1993 showed a m utagenicity of 87-1213 revertants per 0.05 g blue rayon extract toward s S. typhimurium YG1024 in the presence of S9 mix. Samples from most s ites taken in December 1993, which follows the rainy season, showed a lower mutagenicity than those taken in May, possibly due to dilution b y the larger volume of water in the river and canals in December. Wate r samples from the Sumida river were collected in July 1993 and Februa ry 1994, and those from the Ara river in January 1994. Mutagenicity of samples from all sites of the Sumida and Ara rivers, which were locat ed 2-30 and 2-20 km, respectively, from the river mouth was also clear ly detected in the presence of S9 mix and did not differ much, being 1 55-748 revertants of YG1024 per 0.05 g blue rayon extract. These resul ts demonstrated that the water in all three rivers contained some fram eshift mutagens.