Trace Levels of Radiation from Fukushima Found in Albacore Tuna

The albacore tuna caught off the Pacific Northwest were found to carry trace amounts of radiation linked to the 2011 Fukushima Daiichi nuclear disaster in Japan.

Researchers at the Oregon State University found that the albacore tuna had slightly elevated levels of radiation most probably from Fukushima, but the concentration was much lower than the maximum safe level set by the U.S. Department of Agriculture.

The Fukushima nuclear disaster was a result of an intense 9.0 magnitude earthquake and tsunami.  The disaster led to leakage of unknown quantities of radioactive materials into the waters.  There was always a fear that the ocean currents would carry the radioactive materials, mainly radioactive cesium-137 and cesium-134, to the California coast.

The researchers claim that in order to reach the amount of radiation the average person is annually exposed to in everyday life through cosmic rays, air, X ray and other sources, one must consume over 700,000 pounds of the fish with the highest radioactive level. The levels of radiations found in the fish were too small to be harmful or cause concern.

In this study the researchers analyzed nearly 26 Pacific albacore that were caught off the coast between 2008-2012. The analysis was done in order to compare the pre-Fukishima and post-Fukushima radiation levels.

The researchers observed that levels of some specific radioactive isotopes soared and in a few fish there was a three-fold increase in the radiation level.

The researchers measured the levels of radiation in the fish from their loins, carcass and guts. They found barely any traces but  the study is important because it is one of the first to look at various 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 on the study.

Next they looked at the radionuclide levels in various aged fish and noticed that levels of radiation were high in four-year-old albacore compared to the younger ones, indicating that the e 4-year-old albacore might have passed through the Fukushima plume twice. Most of the three year old albacore did not have any traces of the radiation.

It is possible that further exposure to the plume could elevate the levels of radiation in albacore but it would still be low. And these fishes mature and turn 5, they would stop migrating to long distances and would travel toward the south to subtropical waters.

The researchers say that very little is known about the migrating habits of young albacores before they enter the waters of U.S. "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."

The finding was published in the journal Environmental Science and Technology.