Woods Hole Q&A on #Fukushima Radiation and Fish

Ken Buesseler at Woods Hole Oceanographic Institution has been researching the marine life and how it is affected by the Fukushima I Nuclear Power Plant accident that has released significant amount of radioactive materials into the Pacific Ocean.

He has a page with questions that he gets from people concerned about the radiation in marine life and his answers.

From Q&A by Ken Buesseler at Woods Hole Oceanographic Institution (emphasis in the answers is mine):

What is the state of fisheries off Japan and along U.S. West Coast?

The coastal fisheries remain closed in Japan near Fukushima, where there is a concern for some species, especially the bottom dwelling ones, which are being tested and many have been found to be above the Japanese government's strict limits for cesium in seafood. These contaminated fish are not being sold internally in Japan or exported. Because of the dilution that occurs even a short distance from Fukushima, we do not have a concern about the levels of cesium and other radionuclides in fish off the West Coast of the U.S.

More about the state of Japanese fisheries (pdf).

Are fish such as tuna that might have been exposed to radiation from Fukushima safe to eat?

Seawater everywhere contains many naturally occurring radionuclides, the most common being polonium-210. As a result, fish caught in the Pacific and elsewhere already have measurable quantities of these substances. Most fish do not migrate far from home, which is why fisheries off Fukushima remain closed. But some species, such as the Pacific bluefin tuna, can swim long distances and could pick up cesium in their feeding grounds off Japan. However, cesium is a salt taken up by the flesh that will begin to flush out of an exposed fish soon after they enter waters less affected by Fukushima. By the time tuna are caught in the eastern Pacific, cesium levels in their flesh are 10-20 times lower than when they were off Fukushima. Moreover, the dose from Fukushima cesium is considered insignificant relative to the dose from naturally occurring polonium-210, which was 1000 times higher in fish samples studied, and both of these are much lower relative to other, more common sources, such as dental x-rays.

More about the dose and associated risk (pdf) of radiation from Fukushima to marine life and humans.

Is there concern about other radionuclides, such as strontium-90?

The continued release of radionuclides from groundwater and leaking tanks at Fukushima nuclear power plants site needs to be watched closely, as the character or mix of radionuclides is changing. One example is the higher levels of strontium-90 contained in groundwater and storage tanks that are leaking into the ocean. Because strontium-90 mimics calcium, it is taken up by and concentrated in bones, where it remains for long periods of time (it has a half-life of 30 years and calcium/strontium is not replaced as quickly in the body as cesium). If leaks of strontium-90 continue, this radionuclide could become a larger concern in small fish such as sardines, which are often eaten whole. So far, however, evidence suggests that levels in fish of strontium-90 remains much lower than that of cesium-137.

Is radiation exposure still a concern?

I stood on a ship two miles from the Fukushima reactors in June 2011 and as recently as May 2013, and it was safe to be there (I carry radiation detectors with me) and collect samples of all kinds (water, sediment, biota). Although radioactive isotopes in the samples and on the ship were measurable back in our lab, it was low enough to be safe to handle samples without any precautions. In fact, our biggest problem is filtering out natural radionuclides in our samples so we can measure the trace levels of cesium and other radionuclides that we know came from Fukushima.

Where does radiation from Fukushima go once it enters the ocean?

The spread of cesium once it enters the ocean can be understood by the analogy of mixing cream into coffee. At first, they are separate and distinguishable, but just as we start to stir the cream forms long, narrow filaments or streaks in the water. The streaks became longer and narrower as they moved off shore, where diffusive processes began to homogenize and dilute the radionuclides. In the ocean, diffusion is helped along by ocean eddies, squirts, and jets that broaden, mix, and continue to dilute the cesium as it travels across the ocean. With distance and time, radionuclide concentrations become much lower in the ocean, something that our measurements confirm.

More information about our oceanographic studies off Fukushima (pdf).

Are the continued sources of radiation from the nuclear power plants of concern?

The site of the Fukushima Dai-ichi nuclear power plant is an ongoing source of radionuclides (pdf) in to the ocean—something I've seen evidence of in my data and published about since 2011. Although the numbers sound large (300,000 gallons of water leaked or 20 trillion bequerels [sic] per liter), we calculated in 2011 when radiation levels were much higher than today that the dose to someone on a ship or in the ocean was not of concern. For the workers at the site, direct exposure from leaking storage tanks is of greater health concern because exposure from these concentrated sources is much higher. For the general public, it is not our direct exposure, but uptake by the food web and, hence, the potential for human consumption of contaminated fish that is the main health concern.

Will radiation be of concern along U.S. and Canadian coasts?

Levels of any Fukushima contaminants in the ocean will be many thousands of times lower after they mix across the Pacific and arrive on the West Coast of North America some time in late 2013 or 2014. This is not to say that we should not be concerned about additional sources of radioactivity in the ocean above the natural sources, but at the levels expected even short distances from Japan, the Pacific will be safe for boating, swimming, etc.

Is debris washing ashore on the US/Canadian West Coast of concern?

Debris washed out to sea by the tsunami does not carry Fukushima radioactive contamination—I’ve measured several samples in my lab. It does, however, carry invasive species, which will be of serious concern to coastal ecosystems on the West Coast.

Have there been increased deaths as a result of radiation from Fukushima?

Reports of increased deaths are simply not true. Read this reasoned response in Scientific American to the most often-cited "scientific" paper about erroneously linking deaths to radiation from Fukushima. That article ends “This is not to say that the radiation from Fukushima is not dangerous (it is), nor that we shouldn’t closely monitor its potential to spread (we should).” I agree with that statement.

Where can people go for reliable information?

Here are some other links I have passed to others.
Fukushima's Radioactive Water Leak: What You Should Know
http://news.nationalgeographic.com/news/energy/2013/08/130807-fukushima-radioactive-water-leak/
Latest Radioactive Leak at Fukushima: How Is It Different?
http://news.nationalgeographic.com/news/energy/2013/08/130821-fukushima-latest-leak-how-is-it-different/
See also following article from the Woods Hole Oceanographic Institution (w/ links to many others)
http://www.whoi.edu/oceanus/viewArticle.do?id=167749&sectionid=1000
From the special issue of Oceanus Magazine devoted to the cause and impacts of Fukushima:
http://www.whoi.edu/oceanus/series/fukushima
Consider supporting our new Center for Marine and Environmental Radioactivity and check out CMER public education links, such as ABCs of radioactivity
http://www.whoi.edu/page.do?pid=119836

(I wish he didn't mention the dental x-rays...)

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Ministry of the Environment: "Tsunami Debris May Have Already Reached North America, Back in February..."

Oops. Woods Hole Oceanographic Institution just recently released a paper saying the debris may reach North America in 1 to 2 years (see Huffington Post, 4/3/2012).

From Jiji Tsushin (4/6/2012):

既に北米沿岸到達か＝震災漂流物で予測－環境省

Ministry of the Environment's Forecast of disaster debris in the ocean: it may have already reached North America

　環境省は６日、東日本大震災の津波で生じた海洋漂流物の動きに関する予測結果を発表した。それによると、ブイなど海面上に浮かんでいて風の影響を受けやすい漂流物の一部は、太平洋を東へ流れ、今年２月にカナダ西海岸の沿岸に達している可能性があることが分かった。

The Ministry of the Environment announced its forecast of the movement of the disaster debris in the [Pacific] ocean after the March 11, 2011 tsunami. According to the forecast, part of the debris floating on the surface of the ocean that is more easily affected by winds may have traveled across the Pacific Ocean and reached the west coast of Canada in February this year.

　漂流物の大半を占める壊れた家屋などのがれき１３３万トンについて同省が試算したところ、２０１３年２月には、がれきの約３％に当たる約４万１３００トンが北米西海岸の沖合１０キロの範囲に到達する見込み。

The Ministry's forecast of 1.33 million tonnes of debris from houses that got swept away, which consists the majority of the debris, shows about 3% of this type of debris, or about 41,300 tonnes, may reach within 10 kilometers off the west coast of North America by February 2013.

I can't find a press release on the subject at the Ministry's website. If the Ministry is to be believed, the first debris took only 11 months, instead of 1 to 2 years (I remember they were counting on two years).

Even the NOAA seems to have changed the story a little bit, and now says "NOAA researchers are currently relying on computer models to predict the debris items’ path and drift rate, but it's possible that some buoyant materials are reaching U.S. shorelines right now."

By the way, the Huffington Post article is more about the radioactivity of seawater, but here are some clarifications for readers who will go read it and get confused. The writer says:

Even so, Buesseler said, the radioactivity levels are still below what is allowed in food in Japan, which is 500 Bq per kilogram of "wet" weight.

Not any more. As of April 1, 2012, that level is 100 Bq/kg, and it's only for radioactive cesium.

The writer also says:

And while cesium was present in the fish, it doesn't accumulate up the food chain the way polychlorinated biphenyls (PCBs) or mercury do.

That's what Japan's Fisheries Agency claimed last year, right after the accident occurred. It does accumulate up the food chain, particularly when there is a constant supply of radioactive cesium in the environment.

And:

The researchers also found silver-110, but it wasn't clear that was from the Fukushima plant.

Most likely, they detected Ag-110m, which has a half life of 250 days. It would be definitely from the Fukushima plant.

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Woods Hole's Study of Radioactivity in Pacific Ocean in June 2011: "Not Likely to Be Direct Threat" to Marine Life

(UPDATE: The researcher seems to have had a change of heart somewhat since December. See my latest post.)

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Woods Hole Oceanographic Institute did the only marine survey by international researchers approved by the Japanese government in June 2011. The summary of the survey result, I just found out, was posted on their website on December 6, 2011.

Their conclusion:

Their study finds the levels of radioactivity, while quite elevated, are not a direct exposure threat to humans or marine life, but cautions that the impact of accumulated radionuclides in marine sediments is poorly known.

From Woods Hole Oceanographic Institute press release (12/6/2011; emphasis is mine):

Researchers Assess Radioactivity Released to the Ocean from the Fukushima Dai-Ichi Nuclear Power Facility

With news this week of additional radioactive leaks from Fukushima nuclear power plants, the impact on the ocean of releases of radioactivity from the plants remains unclear. But a new study by U.S. and Japanese researchers analyzes the levels of radioactivity discharged from the facility in the first four months after the accident and draws some basic conclusions about the history of contaminant releases to the ocean.

The study, conducted by Woods Hole Oceanographic Institution chemist Ken Buesseler and two Japanese colleagues, Michio Aoyama of the Meteorological Research Institute and Masao Fukasawa of the Japan Agency for Marine-Earth Science and Technology, reports that discharges from the Fukushima Dai-Ichi nuclear power plants peaked one month after the March 11 earthquake and tsunami that precipitated the nuclear accident, and continue through at least July. Their study finds the levels of radioactivity, while quite elevated, are not a direct exposure threat to humans or marine life, but cautions that the impact of accumulated radionuclides in marine sediments is poorly known.

The release of radioactivity from Fukushima—both as atmospheric fallout and direct discharges to the ocean—represent the largest accidental release of radiation to the ocean in history. Concentrations of cesium-137, an isotope with a 30-year half life, at the plants's discharge point to the ocean, peaked at over 50 million times normal/previous levels, and concentrations 18 miles off shore were much higher than those measured in the ocean after the Chernobyl accident 25 years ago. This is largely due to the fact that the Fukushima nuclear power plants are located along the coast, whereas Chernobyl was several hundred miles from the nearest salt water basins, the Baltic and Black Seas. However, due to ocean mixing processes, the levels are rapidly diluted off the Northwest coast of Japan.

The study used publically available data on the concentrations of cesium-137, cesium-134, and iodine-131 as a basis to compare the levels of radionuclides released into the ocean with known levels in the sea surrounding Japan prior to the accident. Impacts of the Fukushima Nuclear Power Plants on Marine Radioactivity is published in the latest issue of Environmental Science & Technology and is available on the journal's website. Buesseler received funding support for this work from the Gordon and Betty Moore Foundation and the National Science Foundation’s Chemical Oceanography program.

The investigators compiled and analyzed data on concentrations of cesium and iodine in ocean water near the plants’s discharge point made public by TEPCO, the electric utility that owns the plants, and the Japanese Ministry of Culture, Sports, Science and Technology (MEXT). The team found that releases to the ocean peaked in April, a fact they attribute to “the complicated pattern of discharge of seawater and fresh water used to cool the reactors and spent fuel rods, interactions with groundwater, and intentional and unintentional releases of mixed radioactive material from the reactor facility.” They also found that the releases decreased in May by a factor of 1000, “a consequence of ocean mixing and a primary radionuclide source that has dramatically abated,” they report.

While concentrations of some radionuclides continued to decrease, by July they were still 10,000 times higher than levels measured in 2010 off the coast of Japan. This indicates the plants “remain a significant source of contamination to the coastal waters off Japan,” they report. “There is currently no data that allow us to distinguish between several possible sources of continued releases, but these most likely include some combination of direct releases from the reactors or storage tanks, or indirect releases from groundwater beneath the reactors or coastal sediments, both of which are likely contaminated from the period of maximum releases.”

Buesseler says that at levels indicated by these data the releases are not likely to be a direct threat to humans or marine biota in the surrounding ocean waters, but says there could be concern if the source remains high and radiation accumulates in marine sediments. “We don’t know how this might impact benthic marine life, and with a half-life of 30 years, any cesium-137 accumulating in sediments or groundwater could be a concern for decades to come,” he said.

In June, Buesseler led the first international, multidisciplinary assessment of the levels and dispersion of radioactive substances in the Pacific Ocean off the Fukushima Dai-Ichi nuclear power plants—a major research effort also funded by the Gordon and Betty Moore Foundation. During the research expedition, a group of 17 researchers and technicians spent two weeks aboard the University of Hawaii research vessel R/V Kaimikai-O-Kanaloa examining many of the physical, chemical, and biological characteristics of the ocean that determine the fate of radioactivity in the water and potential impact on marine biota. The results of their initial assessments will be presented in Salt Lake City in February 2012 at the Ocean Sciences Meeting, an international gathering of more than 4,000 researchers sponsored by The Oceanography Society, the American Society of Limnology and Oceanography, and the American Geophysical Union.

While international collaborations for comprehensive field measurements to determine the full range of isotopes released are underway, it will take some time before results are available to fully evaluate the impacts of this accident on the ocean.

"However, due to ocean mixing processes, the levels are rapidly diluted off the Northwest coast of Japan." - Uh... northwest? Fukushima I Nuclear Power Plant is in the northeast part of Japan.

That aside, I am puzzled by their conclusion that the releases of radioactive materials into the seawater, which is on-going, are not likely to be a direct threat to marine life, when fish and abalones from the coastal water of northeast Japan have been found with high concentration of radioactive cesium and radioactive silver. Researchers have found plankton far off the coast of Fukushima with concentrated radioactive cesium.

Is it possible that all the Woods Hole researchers took as samples was ocean water, and not marine life (plankton, seaweeds, fish, shellfish, etc.)?

Or are they saying few hundred becquerels/kg of radioactive cesium won't affect the fish?

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