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Researchers say they have “unequivocal evidence” that bluefin tuna carried radioactive material all the way from the Fukushima nuclear power plant disaster in Japan to the coast of California.

The Fukushima Dai-ichi plants failed after Japan’s earthquake and tsunami in March 2011, releasing radioactive cesium into the ocean. The team wondered whether Pacific bluefin tuna (Thunnus orientalis) off Japan’s coast might have picked up some of this discharge before migrating to California waters.

To find out, the authors tested the muscle tissue of 15 Pacific bluefin tuna caught in August 2011 near San Diego. The tissue contained about 10 times more radioactive cesium than bluefin caught off California’s coast in 2008, the team reports in Proceedings of the National Academy of Sciences. Levels were also about 10 times higher than those in yellowfin tuna caught near California in August 2011.

Radioactive cesium levels in the bluefin tuna were well below the safety limit set in Japan, and the dose is still low compared to natural radioactive potassium and polonium levels in fish. But the researchers suggest that other migratory animals, such as turtles and seabirds, may also be spreading Fukushima’s radioactive discharge far and wide. Roberta Kwok | 28 May 2012

Source: Madigan, D.J., Z. Baumann, and N.S. Fisher. 2012. Pacific bluefin tuna transport Fukushima-derived radionuclides from Japan to California. Proceedings of the National Academy of Sciences doi: 10.1073/pnas.1204859109.

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