Fish caught in waters off the coast of northern Japan, where an earthquake triggered a radiation leak at the Fukushima power plant, are still as contaminated today as a year ago, a study found.
Contamination levels were particularly high among species dwelling at the bottom of the ocean, as sinking radioactive materials tainted the seafood, the research showed. The findings, published today in the journal Science, suggest there is a continued source of radiation from the seafloor that will have a lasting impact, said Ken Buesseler, the study’s author.
“This means that even if these sources were to be shut off completely, the sediments would remain contaminated for decades to come,” said Buesseler, a senior scientist at Woods Hole Oceanographic Institution in Woods Hole, Massachusetts.
In waters off Fukushima, where there is a ban on fishing for bottom-dwelling species, 40 percent of fish are above the limit for human consumption based on Japanese regulatory limits, Buesseler said.
The devastation from the March 2011 earthquake, tsunami and radiation leaks at the Fukushima Dai-Ichi nuclear plant continue to harm Japan’s 1.5 trillion yen ($18 billion) fish industry. The tsunami damaged 319 ports, 28,612 fishing boats and 1,725 facilities such as processing plants in Japan and the cost totaled about 1.26 trillion yen as of March, the country’s fisheries agency said in latest annual report.
About 3,500 terabecquerels of radioactive cesium 134 and 3,600 terabecquerels of cesium 137 may have leaked into the sea between March 26 and Sept. 30 last year after a three-reactor meltdown at the Fukushima Dai-Ichi nuclear plant, operator Tokyo Electric Power Co. said in a statement in May.
More than 80 percent of the radioactivity from the nuclear plant was released offshore or into the ocean from waters used for cooling, according to the study.
Radioactive cesium levels in seafood haven’t dropped as of August, except perhaps in fish that live near the surface, Buesseler said. Two greenlings caught in August closer to shore off Fukushima contained more than 25,000 becquerels per kilogram, compared with the maximum permissible level of 100 bq/kg set by the Japanese government, the author said.
“An understanding of sources and sinks of cesium and other radionuclides is needed to predict long-term trends in fish and other seafood,” Buesseler said.
Such knowledge would support better decision making, reduce public concern and potentially help to restore safety and confidence in local fisheries, he said.