Radioactive Cesium found in plankton almost 375 miles from Fukushima nuclear plant

TOKYO -- Radioactive cesium believed to have been released during the crisis at the Fukushima No. 1 nuclear power plant in Japan following last year's major earthquake has been found in plankton about 600 kilometers (nearly 375 miles) east of the facility, according to a Japan-U.S. joint research team.

The amount of cesium detected in the plankton was far below the government's provisional limit of 500 becquerels per kilogram for marine products, according to the team led by Jun Nishikawa, research associate at the University of Tokyo's Atmosphere and Ocean Research Institute.

However, follow-up studies will be necessary because the radioactive cesium is likely to have accumulated in fish that eat plankton, the team said.

The findings will be reported to a conference of the Oceanographic Society of Japan set for Tuesday.

The research team collected animal plankton at 17 locations between 30 kilometers (18.6 miles) and 600 kilometers (372.8 miles) east of the plant in June last year, about three months after the March 11 earthquake and tsunami that triggered the nuclear crisis.

Cesium-137 was detected in all of the collected plankton, which in a dry state was found to contain 0.3 to 56.4 becquerels per kilogram. The farther away the plankton was collected, the less radiation it contained, according to the team. Read More