Though the vast majority of fish tested off Japan’s northeast coast remain below recently tightened limits of cesium-134 and cesium-137 in food consumption, Japanese government data shows that 40% of bottom-dwelling fish such as cod, flounder and halibut are above the limit, Ken Buesseler, a marine chemist at the Woods Hole Oceanographic Institution in Massachusetts, wrote in an article published Thursday in the journal Science.
In analyzing extensive data collected by Japan’s Ministry of Agriculture, Fisheries and Forestry, he found that the levels of contamination in almost all kinds of fish are not declining a year after the March 11, 2011 disaster. An earthquake and tsunami knocked out the Fukushima Daiichi plant’s vital cooling system, causing three reactor cores to melt and spew radiation onto the surrounding countryside and ocean.
“The (radioactivity) numbers aren’t going down. Oceans usually cause the concentrations to decrease if the spigot is turned off,” Buesseler told The Associated Press in an interview. “There has to be somewhere they’re picking up the cesium.”
“Option one is the seafloor is the source of the continued contamination. The other source could be the reactors themselves,” he said.
The safety of fish and other foods from around Fukushima remains a concern among ordinary Japanese, among the world’s highest per capita consumers of seafood.
Most fish and seafood from along the Fukushima coast are barred from the domestic market and export. In June, authorities lifted bans on octopus and sea snails caught off Fukushima after testing showed very low levels of radiation.
But the most contaminated fish found yet off Fukushima were caught in August, some 17 months after the disaster. The two greenlings, which are bottom-feeders, had cesium levels of more than 25,000 becquerels per kilogram, 250 times the level the government considers safe.
A government fisheries official, Chikara Takase, acknowledged that the figure for the greenlings was “extremely high,” but he added high numbers were detected only in limited kinds of fish sampled in the restricted waters closest to the plant. He acknowledged that “we have yet to arrive at a situation that allows an overall lifting of the ban.”
To bolster public confidence in food safety, the government in April tightened restrictions for cesium-134 and cesium-137 on seafood from 500 to 100 becquerels per kilogram. But the step led to confusion among consumers as people noticed more products were barred.
Plant operator Tokyo Electric Power Co said some radioactive water used to cool the Fukushima reactors leaked into the ocean several times, most recently in April.