The finding reported last week that bluefin tuna caught off southern California carried low levels of nuclear radiation from Japan was another signal the world's food chain could be compromised. It also showed how efficient natural systems are at distributing radioactivity from the Fukushima-Daiichi plant that blew up last year.



Bluefin tuna spawn only off the coasts of Japan and the Phillippines, and some migrate to the waters off southern California and Baja. The tuna caught off southern California, according to the study published in the Proceedings of the National Academy of Sciences, contained elevated levels of cesium 134 -- a radioactive isotope otherwise absent in the Pacific Ocean and linked with nuclear production. The fish also contained elevated levels of cesium 137, already present in the eastern Pacific.



The findings were a surprise to the researchers. But they prompted no warnings that eating bluefin tuna would pose an increased cancer risk, because even the elevated radioactivity levels detected were well below thresholds considered safe. more from