The news this week that tuna caught in California had picked up radioactive contamination from the Fukushima nuclear plant last year might sound scary. But one of the experts who made the discovery says he's not too concerned about the health effects.
Nicholas Fisher, a distinguished professor in the School of Marine and Atmospheric Sciences at Stony Brook University in New York, co-wrote the study that appeared this week in the journal Proceedings of the National Academy of Science. He says the amount of artificial radiation found in the fish was actually quite low. In fact, it worked out to about three per cent of the radiation that can be found in the fish naturally.
"All fish -- in fact, all marine life -- are naturally radioactive with naturally-occurring radionuclides that have existed in the ocean since before man ever appeared on the planet," Fisher explained to CTV News Channel Wednesday.
Fisher says he was most struck by the fact that the fish were still carrying man-made radiation after swimming across a massive ocean. But he insists the levels of radiation picked up by his team's highly sensitive instruments were still far below safety limits imposed by governments, including those of the U.S. and Japan.
"The total amount is very low. It's detectable, but it's not a serious cause for concern," he said.
"I don't want to tell people what they should or should not eat," he later added, "but I personally would not be terribly anxious about consuming fish that are 3 per cent more radioactive than the natural radiation background. That's extremely low levels."
Fisher said his team feels certain that the artificial radiation they found in the tuna -- cesium-134 and cesium-137 -- did come from the radioactive waste that trickled into the ocean after a series of explosions at the Fukushima plant in Japan in March, 2011.
He says they know that because the team also analyzed yellowfin tuna that were also caught off California.
Unlike the bluefin tuna, which spawn in the waters near Japan and then cross the ocean to North America, yellowfin tend to stay in the waters off California their whole life. And the yellowfins they tested had very little artificial radioactivity.
They found no trace at all of cesium-134 in the yellowfins, and only background levels of cesium-137 which they believe was left over from nuclear weapons testing in the 1960s.
"So we think there's pretty unequivocal evidence that the radiation that was detected in the tuna came from Fukushima, but it was picked up by the fish in Japanese waters, not in California waters."
While this news might convince some to stay away from sushi-grade tuna for a while, it's interesting to note that plenty of the food we eat every day contains radiation.
Bananas, for example, are loaded with potassium, which is one of the fruit's known health benefits. But potassium also contains the naturally occurring radionuclide (or radioisotope) potassium-40, which decays naturally and emits radiation. Potatoes also emit radiation as do nuts (especially Brazil nuts), lima and kidney beans.
