April 30, 2014
Pacific Albacore Study Finds Insignificant Traces Of Fukushima Radiation
Lawrence LeBlond for redOrbit.com - Your Universe Online
When the Fukushima Daiichi nuclear power plant was destroyed in 2011 after a massive earthquake and deadly tsunami, contamination of sea water and sea life was a major concern. However, albacore tuna recently caught off the Oregon shore had only slightly elevated levels of radioactivity, not enough to be of alarm, according to a new study published in the journal Environmental Science and Technology.
The study team, led by Delvan Neville, a graduate research assistant in the Department of Nuclear Engineering and Radiation Health Physics at OSU, determined that the amount of radioactivity is so minute, that a person would have to eat more than 700,000 pounds of the fish with the highest radioactive level just to match the amount of radiation the average person is typically exposed to on a daily basis – which comes from cosmic rays, air, ground, X-rays and other sources.
“You can’t say there is absolutely zero risk because any radiation is assumed to carry at least some small risk,” said Neville. “But these trace levels are too small to be a realistic concern.”
Neville said that eating tuna tainted with caesium traces for a full year would offer about the same dosage of radiation as one would get from spending 23 seconds in the presence of radon gas, or perhaps “sleeping next to your spouse for 40 nights from the natural potassium-40 in their body.”
“It’s just not much at all,” Neville maintained.
For the study, Neville and colleagues examined 26 Pacific albacore caught off the coast of Oregon between 2008 and 2012 to give them a comparison between radiation levels from before the Fukushima disaster and afterward. They discovered that levels of specific radioactive isotopes did increase, but even at the most extreme level, they only tripled – a measurement that is only 0.1 percent of the radio-cesium level set by the US Food and Drug Administration for concern and intervention.
The team tested the samples of fish from their loins, carcasses and guts and found varying levels of cesium – all barely detectable. Still, these findings are important, noted the authors, 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 on the study.
Next, the team looked at the radionuclide levels in fish of differing ages. They found that four-year-old albacore had somewhat higher levels of radionuclide than younger fish. This suggests that younger fish had only made the trans-Pacific migration once, while the four-year-olds may have migrated through the Fukushima plume twice.
The team found that the majority of three-year-old fish had no traces of Fukushima radiation at all.
Neville and team did note, however, that it is possible that additional exposures to the Fukushima plume could increase radiation levels in albacore. Still, the levels would remain low enough that it would not pose a significant threat, they maintained. And once albacore reach the age of five, they stop migrating long distance and move to subtropical waters in the Central and West Pacific and do not return to the western US coast.
“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 migration patterns of albacore before they enter the US fishery at about three years of age, according to Phillips.
“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.”
While the findings should not be viewed as worrisome, the authors did note the significance of the discovery.
"I think people would rather have an answer on what is there and what isn't there than have a big question mark," Neville said in a statement to Reuters. "The levels were way too small to really be a food safety issue, but we still want to tell people about it so they know what's there."
Phillips said he didn’t expect to find high levels of radiation in the albacore, but thought it would be a good way to track the migratory patterns of the fish. Thanks to the continued support from the Oregon Sea Grant, the research will continue to expand the pilot program to look at fish from California and other parts of the North Pacific, he added.
Phillips said the team looked at Pacific albacore because its migratory routes connect with Japan. "If we were going to see it in something, we would see it in albacore' or other high level predators," he told Reuters.