Marine ecologists from Stanford University on Monday published a paper saying they found elevated levels of radioactive cesium in Pacific bluefin tuna caught off the waters of Southern California. The Associated Press reports the levels of radioactive cesium were 10 times higher than the amount measured in tuna off the California coast in previous years. But even so, that’s still far below safe-to-eat limits set by the U.S. and Japanese governments.
Bluefin tuna absorbed radioactive cesium from swimming in contaminated waters and feeding on contaminated prey such as krill and squid, the scientists said. As the predators made the journey east, they shed some of the radiation through metabolism and as they grew larger. Even so, they weren’t able to completely flush out all the contamination from their system.
Soon after the Fukushima disaster, scientists were pointing out that it’s hard to say where the tuna on your sashimi plate originates. Even if fish pass through contaminated waters off the coast of Fukushima, it’s unlikely they would stick around long enough for much radioactive cesium to build up in their bodies.
“That’s a big ocean. To swim across it and still retain these radionuclides is pretty amazing,” Nicholas Fisher, one of the researchers reporting the findings online Monday in the Proceedings of the National Academy of Sciences, said.
The U.S. Food and Drug Administration notes in a bulletin that radioactive iodine, which has a short half-life, would be gone by the time migratory fish arrive in U.S. waters, and that radioactive cesium hasn’t been detected in any tuna imported from Japan.
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