Albacore tuna caught off the Oregon coast since the 2011 Fukushima Daiichi power plant meltdown in Japan has slightly elevated levels of radioactivity, according to a new study by Oregon State University.
The disaster, which followed a 9.0-magnitute earthquake and tsunami, led to leakage of unknown quantities of radioactive materials into the Pacific. There has been fear - hysteria on the part of some - that ocean currents would carry the radioactive materials, mainly radioactive cesium-137 and cesium-134, to the California (and Oregon) coast and into the fish populations.
But scientists found just trace amounts in the West Coast tuna. You'd have to consume more than 700,000 pounds of the fish with the highest radioactive level to match the amount of radiation the average person is annually exposed to in everyday life through cosmic rays, the air, the ground, X-rays and other sources, the authors say.
Results of the study are being published in the journal Environmental Science and Technology.
"You can't say there is absolutely zero risk because any radiation is assumed to carry at least some small risk," said Delvan Neville, a graduate research assistant in the department of nuclear engineering and radiation health physics at Oregon State and lead author of the study. "But these trace levels are too small to be a realistic concern.
"A year of eating albacore with these cesium traces is about the same dose of radiation as you get from spending 23 seconds in a stuffy basement from radon gas, or sleeping next to your spouse for 40 nights from the natural potassium-40 in their body," he added. "It's just not much at all."
In their study, the researchers examined 26 Pacific albacore caught off the coast between 2008 and 2012 to give them a comparison between pre-Fuskushima and post-Fukushima radiation levels. They discovered that levels of specific radioactive isotopes did increase - in a few fish there was a three-fold increase in the radiation level. But even that tripling came to only 0.1 percent of the radiocesium level set by the U.S. Food and Drug Administration as cause for concern and intervention.
The researchers tested samples of the albacore from the fishes' loins, carcass and guts and found varying levels - but still all barely detectable. The findings are still important, however, since this is one of the first studies to look at different parts of the fish.
"The loins, or muscle, is what people eat, and the bioaccumulation was about the same there as in the carcass," said Jason Phillips, a research associate in OSU's College of Earth, Ocean, and Atmospheric Sciences and co-author of the study.
The researchers next began looking at the radionuclide levels in different aged fish and found they were somewhat higher in 4-year-old albacore than in younger fish. This suggests that the 3-year-old albacore may have only made one trans-Pacific migration, whereas the 4-year-old fish may have migrated through the Fukushima plume twice.
The majority of the 3-year-old fish had no traces of Fukushima radiation at all.
Although it is possible that additional exposures to the plume could further increase radiation levels in the albacore, it would still be at a low level, the researchers say. Additionally, as albacore mature at around age 5, they stop migrating long distances and move south to subtropical waters in the central and west Pacific - and, even better, do not return to the West Coast of the United States.
"The presence of these radioactive isotopes is actually helping us in an odd way - giving us information that will allow us to estimate how albacore tuna migrate between our West Coast and Japan," Neville said.
Little is known about the migration patterns of young albacore before they enter the U.S. fishery at about 3 years of age, Phillips said.
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"That's kind of surprising, considering what a valuable food source they are," Phillips said. "Fukushima provides the only known source for a specific isotope that shows up in the albacore, so it gives us an unexpected fingerprint that allows us to learn more about the migration."
Guess there's always some silver lining. But if you're looking for something to be paranoid about, go ahead and have a tuna meltdown.