Common Dreams, Reuters, and the Guardian (including a video of the Japanese government's response to the news) have reported that bluefin tuna which had migrated from Japan's east coast to the U.S. west coast tested positive for elevated levels of radioactive cesium in August 2011, about four months after massive radioactively contaminated water releases to the Pacific Ocean took place at Fukushima Daiichi. Bluefin tuna is a prized seafood. Although the levels of radioactive cesium-137 and cesium-134 are reportedly lower than Japanese and U.S. permissible levels for consumption, the U.S. National Academy of Science has long maintained that any exposure to radioactivity, no matter how low the dose, carries a health risk of cancer, and that these risks accumulate over a lifetime.
The Reuters article gives the false impression that radioactive cesium-137 is somehow naturally occurring. While Cs-137 was released from atmospheric atomic bomb tests for decades beginning in 1945, and thus can be termed a part of "background" radioactivity levels, this should not be confused with "natural background," for atomic weapons blasts, and their radioactive fallout, are far from "natural." Cs-137, with a 30 year half-life and 300 to 600 year hazardous persistence, was released in large amounts by the Fukushima nuclear catastrophe, especially in March and April 2011. Cs-134, with a 2 year half-life (and 20 to 40 year hazardous persistence), contamination in bluefin tuna is unmistakably of Fukushima Daiichi origin.
In a segment entitled "Charlie the Tuna Glows in the Dark?", Thom Hartmann, host of The Big Picture, interviews Beyond Nuclear's Kevin Kamps about Fukushima's radioactive "chickens (of the sea) coming home to roost," along the California coast.
While NPR (Nuclear Power Radio? National Plutonium Radio?) saw fit to downplay the significance of Fukushima's radioactive cesium-137 in bluefin tuna on the California coast to the point of downright denial, the Chief Cabinet Secretary of the Japanese Prime Minister admitted that a global monitoring network may be needed. Robert Alvarez of Institute for Policy Studies also rebutted NPR's trivialization.