Oregon State University Researchers on Albacore Tuna off Oregon: "you would have to consume more than 700,000 pounds of the fish" to match annual natural background radiation

Probably not what many people want to hear, who have been busy petitioning their local governments on the US west coast about the danger of "high levels" of Fukushima radiation.

According to the press release by Oregon State University, the researchers at Oregon State University and National Oceanic and Atmospheric Administration (NOAA) tested Pacific albacore tuna caught off the coast of Oregon between 2008 and 2012 and compared radioactive cesium levels, the first study to compare "before and after". The study is also the first to compare different parts of the fish.

The study seems to be the continuation of the study they published on October 2012.

The result was that the amount of radioactive cesium in post-Fukushima fish was triple that of pre-Fukushima fish, "at the most extreme level".

From the paper's abstract, here are the numbers, in MILLIBECQUEREL/Kg (millibecquerel=1/1000 of 1 becquerel) in WET WEIGHT:

• Cesium-134: 18.2–356 mBq/kg of wet weight

• Cesium-137: 234–824 mBq/kg of wet weight

Expressed in more familiar Bq/kg,

• Cesium-134: 0.0182 - 0.356 Bq/kg

• Cesium-137: 0.234 - 0.824 Bq/kg

An unexpected side benefit of studying these fish was, according to the researchers, to better understand the albacore tuna migration, using radioactive cesium from Fukushima as a trace.

The press release by Oregon State University (4/28/2014; emphasis is mine):

Study finds only trace levels of radiation from Fukushima in albacore
04/28/2014

CORVALLIS, Ore. – Albacore tuna caught off the Oregon shore after the Fukushima Daiichi power station in Japan was destroyed in a 2011 earthquake had slightly elevated levels of radioactivity but the increase has been minute, according to a newly published study.

In fact, you would have to consume more than 700,000 pounds of the fish with the highest radioactive level – just 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 University and lead author on 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 a total of 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, but at the most extreme level, they only tripled – a measurement that is only 0.1 percent of the radiocesium level set by the U.S. Food and Drug Administration for concern and intervention.

The researchers tested samples of the albacore from their loins, carcass and guts and found varying levels – 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 on 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 the 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 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 pointed out. 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 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 three years of age, Phillips said.

“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.”

Other authors were Richard Brodeur of NOAA’s Northwest Fisheries Science Center, and Kathryn Higley, of the OSU Department of Nuclear Engineering and Radiation Health Physics. The study was supported by Oregon State University and the National Oceanic and Atmospheric Administration, with continued support from Oregon Sea Grant.

The abstract of the paper "Trace Levels of Fukushima Disaster Radionuclides in East Pacific Albacore" (emphasis is mine):

The Fukushima Daiichi power station released several radionuclides into the Pacific following the March 2011 earthquake and tsunami. A total of 26 Pacific albacore (Thunnus alalunga) caught off the Pacific Northwest U.S. coast between 2008 and 2012 were analyzed for 137Cs and Fukushima-attributed 134Cs. Both 2011 (2 of 2) and several 2012 (10 of 17) edible tissue samples exhibited increased activity concentrations of 137Cs (234–824 mBq/kg of wet weight) and 134Cs (18.2–356 mBq/kg of wet weight). The remaining 2012 samples and all pre-Fukushima (2008–2009) samples possessed lower 137Cs activity concentrations (103–272 mBq/kg of wet weight) with no detectable 134Cs activity. Age, as indicated by fork length, was a strong predictor for both the presence and concentration of 134Cs (p < 0.001). Notably, many migration-aged fish did not exhibit any 134Cs, suggesting that they had not recently migrated near Japan. None of the tested samples would represent a significant change in annual radiation dose if consumed by humans.

Researchers at Stanford University and Stony Brook University published the study on Pacific bluefin tuna in June 2013, which revealed radiation exposure from natural radioactive potassium and polonium (alpha nuclide) is significantly greater than exposure from Fukushima-derived radioactive cesium.

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#Radioactive Cesium of Fukushima Origin (Cs-134) Found in Albacore Tuna Caught off Washington, Oregon

(Update) The albacore tested after Fukushima had 340 – 1024 millibequerels/kg of combined cesium, according to Simplyinfo.org. 0.34 to 1.024 becquerels/kg. One-tenth of the bluefin tuna that the Stanford researchers tested.

(H/T anon reader)

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The Seattle Times article below doesn't report the number. It doesn't mention cesium-137 (half-life 30 years) either, which should have been detected alongside cesium-134 if it was of the Fukushima origin.

To avoid "baseless rumor", I suppose. But I still wish the reporter (or the researchers and government officials speaking to him) simply mentioned the number, instead of doing the "Edano" and saying "It's barely detectable, no effect on health, it's just so little ..."

The article says "it is allowing scientists to track the migratory patterns of tuna for the first time", which I take it to mean "the first time in Washington and Oregon". The researchers at Stanford University in California already announced the result of their study of bluefin tuna off southern California in May this year.

From The Seattle Times (10/27/2012; emphasis is mine):

Trace Fukushima radiation found in Northwest albacore tuna

Researchers have found tiny amounts of radioactive cesium in albacore caught off Washington and Oregon. The radiation, originating from the 2011 tsunami in Japan, is thought to pose no public-health risk, but it is allowing scientists to track the migratory patterns of tuna for the first time.

Since the early 1950s, scientists have argued about one of the West Coast's most popular fish — albacore tuna.

Are the silvery streaks that tempt thousands of anglers each year part of one family of highly migratory fish? Or are there really two groups of speedy tuna, each traveling a different route around the sea?

Now this half-century-old argument could be clarified by a disturbing new pollutant: radioactive isotopes from Tokyo's Fukushima Daiichi nuclear power plant.

Oregon State University researchers and federal scientists are finding exceedingly tiny amounts of radioactive cesium in albacore caught off the coast of Washington and Oregon. And it's clear the radionuclide originated with the nuclear accident that followed the deadly tsunami that hit Japan in March 2011.

While some forms of cesium persist in the environment for decades, one isotope scientists saw, cesium-134, has a half-life of a little more than two years and could only have come from that accident.

So far, the trace amounts that OSU scientists found in tuna are far less than anything that would pose a risk to humans; a fish eater would have to consume several thousand pounds of the most radioactive albacore they discovered just to increase by 1 percent the amount of radiation they're exposed to from everyday sources.

"The amounts they found were incredibly small," said Donn Moyer, spokesman for the Washington state Department of Health, which also tested the same samples and came up with the same results. "There's nothing really remarkable about the amounts."

But because cesium decays so quickly, the discovery makes clear that fish caught in Northwest waters picked up the radiation while feeding on smaller fish in or around Japan.

"We're talking about barely, barely detectable levels," said Jason Phillips, who led the work while a graduate student at OSU's College of Earth, Ocean, and Atmospheric Sciences. "But because the radiation has to be derived from Fukushima, they had to pick it up within its vicinity or in the drift."

For most of the 1950s, researchers tagged North Pacific albacore and determined that the fish along the West Coast traveled between here, Japan and California and Mexico.

But in the 1970s researchers began to see signs that suggested some of the California fish might be part of a different population.

"It turns out there may be two different populations," said Richard Brodeur, with the National Marine Fisheries Service. "Ours up here might be completely different from those down off of California."

But the fast travel so far and fast — between 50 and 200 miles in a day — that tracking their movements is almost impossible, and no one has been able to confirm their theory.

After the Fukushima disaster, Phillips and Brodeur and another graduate student in radiation health had an idea: Why not map migration routes for West Coast tuna using the radioactive fish?

So far they've tested 18 Northwest fish, and the results are consistent: Fish caught before the tsunami are radiation free; fish caught afterward contain trace amounts of cesium.

But the real test is yet to come. The scientists have been collecting dozens of albacore from fishermen off the California coast. They plan to test those fish soon. If those don't show the same traces of cesium-134, it would suggest that they didn't travel to the same place as the Northwest fish.

Understanding when and where albacore travel can help scientists protect stocks of a West Coast fish worth tens of millions of dollars annually.

The researchers are presenting their findings to a conference in Italy this weekend.

The Stanford researchers found 4 Bq/kg of cesium-134 (and 6.3 Bq/kg of cesium-137) in bluefin tuna off California, which do migrate. Yellowfin tuna don't, and I'm not aware of any testing or study of the radiation in yellowfin tuna.

Oregon State University's press release on October 24, 2012 is more detailed, but still no number mentioned. The press release does say the researcher detected cesium-137 also, and the fish they tested were caught last year and frozen:

The researchers first identified two Fukushima-linked isotopes – Cesium-137 (Cs-137) and Cesium-134 (Cs-134) – this July, in samples of fish caught and frozen in 2011.

In the OSU press release, the researcher Delvan Neville says they tested about 70 pounds (about 32 kilograms) of tuna, or 18 samples:

“This is what we've seen after testing about 70 pounds of tuna,” Neville said. “When you've run one or two samples, you can't really say much about the population you're testing yet. When you've run five or six, you could make some guesses. When you're up to, at this time, 18 samples and everything has fallen fairly neatly into two groups of results, you can start to make some predictions about that population.

(H/T Kontan_Bigcat)

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