Sludge samples taken at the mouths of two major rivers emptying into Tokyo Bay showed radioactive cesium contamination linked to the Fukushima No. 1 nuclear plant crisis grew by 1.5 to 13 times since August, a researcher at Kinki University said Monday.
The contamination poses no immediate health risk since no seafood from Tokyo Bay has seen contamination levels exceed the government-set threshold. But close, long-term monitoring of the seabed mud is needed, said Hideo Yamazaki, professor at Kinki University's Research Institute for Science and Technology.
"Contamination is flowing into the bay from rivers, including the Edogawa River, where cities with high radiation levels like Kashiwa (in Chiba Prefecture) are located upstream," Yamazaki told The Japan Times.