Researchers at New York's Stony Brook University found that likely doses of radioactivity that consumers may have been exposed to would be less than dosages associated with other commonly consumed foods or medical treatments.
According to a study released last year, scientists detected radioactive cesium, a nuclear reactor byproduct, in tuna caught off the California coast in the months after the triple meltdown at Fukushima Daiichi. The attention that study received led scientists to take another look at the data, said Nicholas Fisher, a marine science professor at Stony Brook University.
"People did not know how to translate that into a dose, or into what risk do I have from eating that tuna," Fisher said, explaining that the new study addresses this issue.
The results, published Monday by the Proceedings of the National Academy of Sciences, found that anyone who eats the bluefin would receive about 5% of the radiation found in a typical banana, which is high in naturally radioactive potassium.
The doses were calculated from fish caught off San Diego in August 2011. A follow-up study with fish caught in 2012 found the amount of cesium dropped by about half in those tuna, Fisher said.
"Even if we use the higher concentrations, the concentrations we measured in 2011, the doses to human consumers are very low, and lower than the naturally occurring radionuclides," he said.
There are other reasons to worry about the bluefin, found in sushi and sashimi, such as mercury contamination. Anyone eating large quantities of the fish over a long period is more likely to develop ill effects from mercury than cancer from radiation exposure, Fisher said.
The three operating reactors at Fukushima Daiichi melted down after the earthquake and tsunami that struck Japan in March 2011. The plant's owner is still trying to manage hundreds of thousands of tons of radioactive water used to cool the reactors, and scientists believe some of that is still entering the Pacific Ocean.
More than 15,000 people died because of the earthquake, but no deaths have been blamed on the meltdowns. In May, the World Health Organization found that only a small group of people will face additional cancer risks because of the accident.
More than 100,000 people have evacuated towns near the plant. Waters around the plant are closed as well, and Japan has tightened its standards to keep any contaminated seafood away from consumers.