At least 462 trillion becquerels of radioactive strontium have leaked to the Pacific Ocean since the March disaster at the Fukushima No. 1 nuclear power plant, making it one of the world's most severe such cases of marine pollution, according to calculations by The Asahi Shimbun.
The Fisheries Agency is doing its own sampling survey to assess the accumulation of radioactive materials in marine life.
The newspaper based its calculations on data released by the plant's operator, Tokyo Electric Power Co., and other sources.
With regard to leakages of radioactive-contaminated water from the No. 2 and No. 3 reactor buildings in April and May, respectively, The Asahi Shimbun relied on two sets of figures.
One was the volume of water that leaked from each reactor building. The other concerned the concentration of radioactive strontium in water that accumulated in each reactor building.
By multiplying the volume of leaked water by the concentration of radioactive strontium, the newspaper calculated the total amount of strontium that leaked from the two reactors.
Besides, the volume of strontium apparently contained in treated water used for cooling purposes that was confirmed to have leaked to the ocean on Dec. 4 was added to that from the No. 2 and No. 3 rectors.
In what is regarded as the world's worst case of marine pollution from a nuclear facility, some 500 trillion becquerels of strontium were discharged to the Irish Sea from the Sellafield nuclear fuel reprocessing facility in Cumbria, Britain, per year in the 1970s.
The volume of strontium that leaked from the Fukushima plant is close to that annual amount.
Strontium accumulates in bones and can cause bone cancer and leukemia.
For this reason, health experts have called for extensive surveys on the amount of leaked strontium so that measures can be drawn up to deal with the problem.
It takes two to three weeks to measure the extent of strontium contamination. Because strontium exists with cesium, and its volume is estimated to be less than 10 percent of that of cesium, few surveys have been done to gauge the volume of strontium in marine life.
The Fisheries Agency has performed surveys only on six kinds of fish through its affiliated organization, the Fisheries Research Agency. The fish, including Pacific cod, were caught in the period from April to July.
The fish were caught about 50 kilometers off the coast of Fukushima Prefecture. According to a Fisheries Agency's announcement on Aug. 30, the amount of strontium detected in Pacific cod came to 0.03 becquerel.
However, a different government survey detected 0.094 becquerel of strontium in fish caught in nearby waters before the disaster at the Fukushima plant.
For this reason, it is unclear whether strontium that had accumulated in the Pacific cod resulted from the crisis in Fukushima.
According to Satoshi Katayama, a professor of marine resources ecology at Tohoku University, detailed studies should be carried out on the accumulation of strontium in fish, such as young Japanese sand lance and white bait, as people generally eat every bit.
"Strontium easily accumulates in creatures, even if its concentration level is low," Katayama said.
- « Prev
- Next »