Archive for the ‘Radiation’ Category
L.A. Times: Alarming West Coast sardine crash likely radiating through ecosystem — Experts warn marine mammals and seabirds are starving, may suffer for years to come — Boats return without a single fish — Monterey Bay: Hard to resist idea that humpback whales are trying to tell us somethingJanuary 6, 2014
6:06 AM (3 hours ago)
- L.A. Times: Alarming West Coast sardine crash likely radiating through ecosystem — Experts warn marine mammals and seabirds are starving, may suffer for years to come — Boats return without a single fish — Monterey Bay: Hard to resist idea that humpback whales are trying to tell us something
- TV: “Massive radioactivity release” at Fukushima going on for almost 3 years now; Visible steam “just the tip of the iceberg” — NHK: Containment vessels are ‘broken’ (VIDEOS)
- “We see radiation from Fukushima in soils in Southern California, especially our desert regions” — High concentrations in seaweed prevented harvest this year — Also found in cattle and chicken feed (AUDIO)
- ABC News: Gov’t, scientists ‘baffled’ over white spots on cows around Fukushima plant — Farmer: No one knows what they are, I think it’s from radiation; “Our town’s contaminated like Chernobyl… We were just thrown away like trash” — Officials order the animals to be slaughtered (VIDEOS)
Some of the hundreds of tons of radioactive water which leaked from a tank at the crippled Fukushima Daiichi nuclear plant may have flown into the sea, the plant’s operator said Wednesday.
Tokyo Electric Power Co (TEPCO) is desperately trying to seal a tank at the plant which has leaked about 300 tonnes of radioactive water.
Spokesman Tsuyoshi Numajiri said traces of radioactivity were detected in a drainage stream.
“There is a possibility that earth and sand contaminated with the leaked water flowed into the drainage. We cannot rule out the possibility that part of the contaminated water flowed into the sea,” he said. “We intend to make detailed examinations of the matter.”
A TEPCO official said the leak was thought to be continuing from the tank but its source had not yet been pinpointed.
The company was also “hurriedly checking” if any of 350 similar tanks at the plant were also leaking.
Numajiri said workers are removing soil contaminated by the leaked water, and pumping the remaining water from the leaky tank.
He said there were no significant changes in radiation levels outside the plant.
Nuclear regulators said the leak represented a level-three “serious incident” on the U.N.‘s seven-point International Nuclear Event Scale (INES), which measures radiation accidents.
“Something that we were very much concerned about has occurred,” Nuclear Regulation Authority (NRA) chairman Shunichi Tanaka told a meeting in Tokyo. “We are in a situation where there is no time to lose.”
The alert, raised from level one which indicates an “anomaly”, is the most serious declared at the ruined plant since March 2011, when a quake-generated tsunami knocked out reactor cooling systems and sparked meltdowns.
The NRA said in a statement the amount of radiation leakage and the “fact that there is no safety protective layer remaining at the facility” meant the level-three warning needed to be declared.
It will now consult the International Atomic Energy Agency (IAEA) on the reassessment, it said.
In Vienna, IAEA spokeswoman Gill Tudor said the agency “views this matter seriously and remains ready to provide assistance on request”.
© 2013 AFP
The most ambitious radiation clean-up ever attempted has proved costly, complex and time-consuming since the Japanese government began it more than two years in the wake of the Fukushima nuclear meltdown. It may also fail.
Doubts are mounting that the effort to decontaminate hotspots in an area the size of Connecticut will succeed in its ultimate aim – luring more than 100,000 nuclear evacuees back home.
If thousands of former residents cannot or will not return, parts of the farming and fishing region could remain an abandoned wilderness for decades.
In many areas, radiation remains well above targeted levels because of bureaucratic delays and ineffective work on the ground. As a result, some experts fears the $15 billion allocated to the scheme so far will be largely squandered.
The deep-seated problems facing the clean-up are both economic and operational, according to a Reuters review of decontamination contracts and interviews with dozens of workers, managers and officials involved.
In Kawauchi, a heavily forested village in Fukushima Prefecture, decontamination crews have finished cleaning up houses, but few of their former inhabitants are prepared to move back. Just over 500 of the 3,000 people who once lived here have returned since the March 2011 meltdown at the Fukushima nuclear plant 25 km to the east.
Even after being deemed safe enough for people to return, Kawauchi has no functioning hospital or high school.
The mushrooms that used to provide a livelihood for foragers are now steeped in dangerous levels of cesium. The only jobs on offer in town are menial. Some houses are so mildewed after three summers of abandonment that they need to be torn down.
The village has not only shrunk; its population has also aged. While the elderly used to make up a third of the town, they now account for 70 percent of residents.
The same pattern has played out across Fukushima as the nuclear accident turned the slow drip of urban flight by younger residents into a torrent, creating a demographic skew that decontamination is unlikely to reverse.
Kawauchi is one of the 11 townships that were most heavily contaminated after the accident, when rain and snow showered radioactive particles onto the verdant hills here as the plume from the plant passed overhead. Half of it lies in the still-evacuated area where the national government has assumed control of the clean-up.
“There is no comprehensive plan on how to rebuild the village,” said Yasutsugu Igari, 34, who works in the reconstruction department at Kawauchi’s village office. “It’s the government that destroyed it, but now it’s doing very little to help us re-create our lives.”
Masayoshi Yokota, who is in charge of decontamination, says he has heard that frustration before.
“First they said they wouldn’t come back unless we decontaminated. So we did that and told them they could come back,” he said. “But then it was about jobs or that they didn’t want to come back because they have children.”
Japan’s plan to scrub clean the area around Fukushima and remove radioactive debris was beset by difficulties from the beginning.
Nothing on the same scale had ever been attempted before. After the Chernobyl accident in 1986, highly contaminated houses were entombed in concrete and the surrounding area was abandoned.
By contrast, Japan’s government is attempting to bring background radiation levels in the most highly contaminated evacuation zone to an average of 1 millisievert per year once all the work is completed.
That would be twice the background radiation level in Denver, or a sixth of the annual dose for the average American when all sources or radiation are taken into account.
Japanese nuclear workers are limited to an accumulative exposure of 100 millisieverts over five years. Although radiation health experts assume that any incremental exposure to radiation increases risks for later cancers, the International Atomic Energy Agency say a statistically significant correlation only shows up at doses over that higher threshold.
The Japanese government decided to allow people to move back to areas with an average annual dose of less than 20 millisieverts in December 2011.
In an attempt to reach the tougher radiation target, thousands of temporary workers have been put to work scrubbing houses and roads, digging up topsoil and stripping trees of leaves into which invisible cesium particles have wormed.
Few of the hundreds of companies and small firms involved have any experience with radiation. Some workers have said they have been told to flush contaminated leaves away in rivers by supervisors to speed the job up and reduce waste, since storage remains a problem.
On a recent Saturday, a crew of 10 workers in jumpsuits, hardhats and surgical masks were clearing a roadside outside Kawauchi, picking up leaves and trimming weeds. The lower half of nearby forest slopes were stripped of saplings and shrubbery.
“That’s lovely,” Yokota told a visitor. “They’ve got it nice and clean.”
Some experts are doubtful about the payback of that effort. First, there is a risk that radioactive isotopes can return to decontaminated areas via wind and rain. Officials in the village of Yugawa found snowfall earlier this year caused radiation levels to spike.
At the same time, the protocols for how to complete the same job vary depending on location. For example, Fukushima city has banned the use of high-pressure water hoses for fear that they simply scatter radioactive particles rather than remove them. Other areas have allowed the hoses to be used, but filtering the collected water produces highly radioactive residue.
“The truth of the matter is that from the European experience (after Chernobyl), remediation factors are disappointing,” said David Sanderson, a professor of environmental science at the University of Glasgow and an expert in radiation, who has made numerous trips to Fukushima to map the fallout.
“And it’s very expensive. I fear there’s a chance the experience in Japan might be pointing to the same conclusion. Unless it succeeds in putting people back in their homes, the benefit is difficult to see.”
Tokyo has budgeted $15 billion for the effort over the past three years, but only a quarter of the $6.5 billion of that provided to the Ministry of the Environment has been spent, according to data provided to Reuters. The target is to finish the project by the end of 2016, although the government of Prime Minister Shinzo Abe has pledged to go faster.
There is also the problem of storage. Most of the contaminated soil and leaves remain piled up in driveways and empty lots because of fierce opposition from local communities to storing it in one place until the Ministry of Environment secures a central site that could hold it for the longer term.
Residents of Tamura, a village in the evacuated zone, were encouraged recently to begin preparing to return to their decontaminated houses – armed with Geiger counters. Some areas still show radiation at twice the target level.
“Decontamination in the true sense of the word is not being carried out,” said Tomoya Yamauchi, a professor of radiation physics at Kobe University. Yamauchi said he found that some decontaminated road surfaces in Fukushima had readings 18 times the target level because caesium had accumulated in cracks in the asphalt.
“I think the government recognizes that Fukushima cannot be returned to how it was.”
Many have given up hope of ever returning to live in the shadow of the Fukushima nuclear plant. A survey in June showed that a third of the former residents of Iitate, a lush village famed for its fresh produce before the disaster, never want to move back. Half of those said they would prefer to be compensated enough to move elsewhere in Japan to farm.
Nuclear evacuees currently receive a living allowance from plant operator Tokyo Electric Power Co (TEPCO), which is cut off when the government decides they are able to move home again.
“I feel like some people don’t want to go back because they’re happy living off the compensation money from TEPCO and they don’t want that to end,” said Hiroaki Inoue, an official from the Ministry of Economy, Trade and Industry spending a year working at the Kawauchi village office to monitor the spending of the reconstruction budget.
But some evacuees say it is unfair to cut off financial support when their previous homes and villages remain unliveable.
“There’s no jobs, no shops open, nothing. It’s become an incredibly difficult place to live and yet they’re saying ‘You can go home now,’” said a single mother evacuated from near Kawauchi, who declined to be named for fear of retribution from the authorities. “It’s so unfair to say that. It’s not that simple.”
In Tomioka, a coastal ghost town north of the Fukushima plant, ambient radiation remains at 10 times the government’s target. Wild boar wander the streets.
“This could be fixed,” said Yokota on a recent visit. “They could get these levels right down. But the thing is, people didn’t come back quickly enough. That’s fatal.”
(c) Copyright Thomson Reuters 2013. Click For Restrictions – http://about.reuters.com/fulllegal.asp
Published on Saturday, April 6, 2013 by Common Dreams
Up to 120 tonnes of radioactive water may have “escaped” from anunderground storage tank at the Fukushima Daiichi nuclear power plant, an official announced Saturday.
The Fukushima Daiichi nuclear power plant. (Photo: IAEA Imagebank via Flickr)”We are transferring the remaining water from the tank to others,” said a Tokyo Electric Power Co (TEPCO) spokesman. The company claims that it is “unlikely” any of the contaminated water found its way into the ocean.
The contaminated water may have leaked from one of the seven underground reservoir tanks which stores water previously used to cool down the nuclear reactors, AFP reports.
ISIS Report 30/05/12
Green tea polyphenol antioxidant protects against bystander effects of low dose ionizing radiation that damage cells and cause numerous diseases including cancer Dr. Mae-Wan Ho
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The recent discovery of bystander effects from low levels of ionizing radiation has thrown risk assessment and radioprotection into disarray  (Bystander Effects Multiply Dose and Harm from Ionizing Radiation, SiS 55). However, it has also led to the discovery of potential mitigating measures against exposure to radioactivity, especially from nuclear accidents like Chernobyl (and Fukushima), the devastation health impacts of which are still surfacing 25 years later  (Chernobyl Deaths Top a Million Based on Real Evidence. SiS 55).
Ionizing radiation has been known to produce free radicals and reactive oxygen species (ROS), predominantly by ionizing water, the most abundant molecules in tissues and cells (see  for an explanation of ROS). ROS are responsible for oxidative damage to DNA, proteins, and lipids, initiating cell death, genomic instability and other consequences of radiation, both in cells that have been directly targeted, and in bystander cells that have not been irradiated . There is evidence that various antioxidants can protect cells against bystander radiation damages, and new findings published online in Mutation Research appear particularly promising.
Ashu Tiku and Benila Richi at Jawaharlal Nehru University, New Delhi and Roasaheb Kale at Central University of Gujarat in India may have found the ideal antioxidant for radioprotectopm .
Non-toxic compound needed for radioprotection
One main problem in radioprotection is to find compounds that are non-toxic or minimally so, and natural compounds fit the bill in being both non-toxic and easily available. Green tea is a rich source of polyphenols with strong antioxidant activities. Green tea extracts and its polyphenols have been shown to possess many health benefits attributed to their antioxidant and anti-inflammatory properties (see [4, 5] Green Tea, The Elixir of Life? and Green Tea Against Cancers, SiS 33). Most of the health benefits of green tea have been credited to the major polyphenol EGCG (epigallocatechin-3-gallate) (Figure 1), which constitutes 55 – 70 % of total polyphenols in green tea extract. Its antioxidant potential is believed to be far greater than vitamin E and vitamin C, the two main antioxidants among vitamins .
Figure 1 EGCG (epigallocatechin-3-gallate) from green tea
The team exposed both pBR322 plasmid DNA as well as spleen cells from mice to g-radiation at different concentrations of EGCG. Preliminary experiments found that EGCG concentrations above 125 mM were toxic to the cells, so the highest concentration used was restricted to 100 mM. The effects of quercetin – another polyphenol found in fruits, vegetables, leaves and grains – and vitamin C were also investigated. The plasmid DNA and cells were incubated for 2 hours with EGCG at different concentrations or quercetin and vitamin C, both at 100 mM, before being irradiated. Afterwards, the plasmid and cells were assessed for DNA damage, and the cells for viability, lipid peroxidation, membrane fluidity, and for activities of enzymes and cofactors involved in detoxification and scavenging of ROS.
Tea compound protects against DNA breaks and cell death
The intact plasmid is supercoiled in a compact form, while the cut plasmid is circular, and the two forms can be clearly distinguished and quantified by electrophoresis. The control (unexposed) sample is about 85% supercoiled. EGCG was found to protect plasmid DNA against breaks at high (50 Gy) or low (3 Gy) dose radiation: >82.5 % protection even at the lowest concentration of EGCG tested (10 mM) and complete 100 % protection at 50 mM. EGCG was better at protection against DNA breaks than quercetin or vitamin C at the same concentration of 100 mM.
The viability of cells was determined with a vital dye that depends on active mitochondria. At 3 to 7 Gy of g-irradiation, cell viability was significantly decreased, and at the highest dose, to 53 % of unexposed controls; but pre-incubation with EGCG protected the cells and restored viability in a concentration dependent manner, at 100 mM, viability was restored to >96 % of control.
Single cell comet assay was used to determine the extent of DNA degradation in the cells. In this assay, cells are trapped in agar gel on a microscope slide, lysed to expose their DNA for electrophoresis, and stained with a fluorescent dye. Cells with intact DNA will appear as a small compact bright spot, while cells with degraded DNA will appear as a diffuse spot with a tail, like a comet, hence the name of the assay. The bigger the tail, the greater is the extent of degradation, which can be quantified with computer software under a fluorescent microscope. Exposing the cells to 3 Gy led to substantial DNA degradation, which was reduced in a concentration dependent manner by EGCG. Quercetin and vitamin C also protected the cells against DNA damage, though not as effectively as EGCG.
Protection against lipid peroxidation
Peroxidation of membrane lipids by ROS destroys membrane structure and function. The results showed that lipid peroxidation increased with radiation dose from 0 to 7 Gy; and membrane fluidity also increased but more slowly. Pre-incubation with EGCG prevented lipid peroxidation and increase in membrane fluidity in a concentration dependent manner. Quercetin and vitamin C similarly protected against peroxidation and increase in membrane fluidity, but again, less efficiently than EGCG.
Key enzyme activities for antioxidant defence restored
Glutathione-S-transferase (GST) is a family of enzymes catalyzing the conjugation of reduced glutathione (GSH) to peroxidized lipids to detoxify them. Reduced glutathione GSH is a tripeptide antioxidant that takes part in reduction-oxidation reactions; in the process, it is oxidized into glutathione disulphide (GSSG). The ratio of reduced to oxidized glutathione is important in the cell’s antioxidant defence. Superoxide dismutase (SOD) catalyses the conversion of superoxide (a reactive oxygen species) into oxygen and hydrogen peroxide and is an important ROS scavenger in cells. Lactate dehydrogenase (LDH) catalyzes the interconversion of pyruvate and lactic acid with simultaneous interconversion of NADH and NAD (reduced and oxidized nicotinamde adenine dinucleotide), which is important in maintaining the cell’s electronic balance and antioxidant defence.
g-irradiation reduced the activities of both GST and SOD. The reduction was countered by EGCG, and also by quercetin and vitamin C. The level of LDH, an indicator of damage was increased in g-irradiated cells, while glutathione was decreased, as indicative of oxidative stress. EGCG was able to counteract those effects, and almost completely at 100 mM. Quercetin was just as effective in reducing LDH and restoring GSH levels to those of controls, but vitamin C less so.
EGCG intercalates in DNA double helix
The authors suggest that EGCG can intercalate in the DNA double helix and protect it from free radical attack. EGCG binding to both DNA and RNA was documented for the first time by researchers at the Tokushima Bunri University and the Saitama Cancer Centre in Japan . They found that EGCG binds to both single-stranded DNA and RNA, as well as double-stranded DNA. Moreover, EGCG binding appears to stabilize double-stranded DNA.
Previous work has also demonstrated that due to the presence of abundant phenolic hydroxyl groups on aromatic rings (see Figure 1), EGCG is a highly efficient free radical scavenger, effectively disarming the free radicals and rendering harmless .
Most importantly, in the absence of g-radiation, EGCG did not have any significant effect. Thus the innocuous habit of drinking two cups of green tea a day may indeed have surprisingly beneficial effects [4, 5] that include protecting against ionizing radiation.
By Stephanie Nebehay
Spikes in radiation caused by the Fukushima nuclear disaster were below cancer-causing levels in almost all of Japan, but infants in one town appear to be at a higher risk of developing thyroid cancer, the World Health Organization said on Wednesday.
In a preliminary report, independent experts said that people in two locations in Fukushima Prefecture may have received a radiation dose of 10-50 millisieverts (mSv) in the year after the accident at the power station operated by TEPCO.
Separately on Wednesday, a U.N. scientific body said that several TEPCO-related workers were “irradiated after contamination of their skin,” but that no clinically observable health effects had been reported.
“Six workers have died since the accident but none of the deaths were linked to irradiation,” said a statement issued in Vienna on the interim findings of a study by the United Nations Scientific Committee on the Effects of Radiation (UNSCEAR).
The 9.0 magnitude earthquake and tsunami on March 11, 2011 wrecked the plant, triggering nuclear meltdowns that contaminated food and water and forced mass evacuations.
Nearly 16,000 people were killed in the earthquake and the tsunami and 3,300 remain unaccounted for.
The areas estimated to have received the highest doses of radiation were Namie town in Futaba and Iitate in Soma, northwest of the stricken plant, the report said.
Infants in Namie were thought to have received thyroid radiation doses of 100-200 mSv, it added. The thyroid is the most exposed organ as radioactive iodine concentrates there and children are deemed especially vulnerable.
“That would be one area because of the estimated high dose that we would have to keep an eye on,” WHO spokesman Gregory Hartl told Reuters. “Below 100 mSv, the studies have not been conclusive.”
Populations exposed to radiation typically stand a greater chance of contracting cancers of all kinds after receiving doses above 100 mSv, according to the United Nations agency. The threshold for acute radiation syndrome is about 1 Sv (1000 mSv).
The local government said in December that the highest exposure levels were in Iitate, where residents were allowed to take their time to leave. It is located 40 km northwest of the plant and outside the 20-km evacuation zone.
The average annual dose from natural background radiation is about 2.4 mSv globally, with a typical range of 1-10 mSv in various regions, according to the 124-page report.
In the rest of Fukushima Prefecture, the effective dose was estimated to be within that band of 1-10 mSv, while effective doses in most of Japan were put at just 0.1-1 mSv.
In the rest of the world, doses were below 0.01 mSv or less, including neighboring Indonesia, the Philippines, South Korea, far eastern parts of Russia, and southeast Asia.
A dose of 0.01 mSv is equivalent to one tenth of the radiation received on a one-stop flight from New York to Tokyo, half the dose received during a chest X-ray, or equal to a dose received during a one-hour visit to one of Egypt’s pyramids.
The report did not deal with radiation exposure suffered by emergency workers or people closest to the disaster site.
“Doses have not been estimated for the zone within 20 kilometers from the Fukushima Daiichi site because most people in the area were evacuated rapidly and an accurate estimation of dose to these individuals would require more precise data than were available,” the report said.
The experts did not examine the short- and long-term health risks for the emergency response workers who worked on the site
– that will be part of a wider WHO report due from a separate group of experts in July. That report will also assess the prospect for long-term increases in cancer cases.
The experts based their assessment on data available up to last September on the amount of radioactivity in air, soil, water and food supplies after the disaster.
Referring to the world’s worst nuclear disaster at Chernobyl in Ukraine in 1986, the report said: “The experience of the Chernobyl accident was that about 30% of the lifetime dose was delivered during the first year and about 70% during the first 15 years.
“On the basis of environmental activity concentration data, it can be expected that the fraction of the lifetime dose beyond the first year will be lower for the Fukushima Daiichi nuclear power plant accident than for the Chernobyl accident,” it said.
(c) Copyright Thomson Reuters 2012.
Officials of Tokyo Electric Power Co (TEPCO) said Thursday that radioactive water containing strontium-90 leaked out of the stricken Fukushima nuclear power plant into the sea.
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years. Its presence in the human body can cause bone cancer, cancer of nearby tissues and leukemia.
TEPCO officials apologized at a news conference for the leakage which occurred early Thursday morning, TBS reported. TEPCO said the leak was from a pipe attached to a temporary decontamination system, and the water had already gone through some of the cleansing process.
The water, once it has been used to cool the reactors, contains massive amounts of radioactive substances such as cesium and strontium, and is put into the water-processing facility so it can be recycled for use as a coolant.
The water is believed to have leaked out for about two hours before it was stopped shortly after 2 a.m., TEPCO said, according to TBS.
TEPCO said it believed that up to 12 tons of waste water containing strontium leaked into the sea.
This is not the first time that strontium has leaked from the Fukushima plant. Last November, radioactive strontium was found in soil in three locations in Tokyo, peaking at 51 becquerels per kilogram. In December, about 150 liters of waste water containing strontium flowed into the sea.
Fukushima’s makeshift water-treatment system has been hit by a series of problems since the government declared the plant was in cold shutdown last December.
Radiation from Fukushima is spreading across the Pacific. (photo: CBS News)
By Jesse Emspak, LiveScience
03 April 12
adioactive material from the Fukushima nuclear disaster has been found in tiny sea creatures and ocean water some 186 miles (300 kilometers) off the coast of Japan, revealing the extent of the release and the direction pollutants might take in a future environmental disaster.
In some places, the researchers from Woods Hole Oceanographic Institution (WHOI) discovered cesium radiation hundreds to thousands of times higher than would be expected naturally, with ocean eddies and larger currents both guiding the “radioactive debris” and concentrating it.
With these results, detailed today (April 2) in the journal Proceedings of the National Academy of Sciences, the team estimates it will take at least a year or two for the radioactive material released at Fukushima to get across the Pacific Ocean. And that information is useful when looking at all the other pollutants and debris released as a result of the tsunami that destroyed towns up and down the eastern coast of Japan.
“We saw a telephone pole,” study leader Ken Buesseler, a marine chemist and oceanographer at WHOI, told LiveScience. “There were lots of chemical plants. A lot of stuff got washed into the ocean.” [Japan Nuclear Radiation Shows Up in US (Infographic)]
The Tohoku earthquake and tsunami of March 11, 2011, led to large releases of radioactive elements from the Fukushima Dai-ichi power plants into the Pacific Ocean. To find out how that radiation spread in the waters off Japan, in June researchers released “drifters” – small monitoring devices that move with the current and take measurements of the surrounding water.
The drifters are tracked via GPS, showing the direction of currents over a period of about five months. Meanwhile, the team also took samples of zooplankton (tiny floating animals) and fish, measuring the concentration of radioactive cesium in the water.
Small amounts of radioactive cesium-137, which takes about 30 years for half the material to decay (called its half-life), would be expected in the water, largely left over from atmospheric nuclear tests in the 1960s and the Chernobyl accident in 1986. But the expedition scientists found nearly equal parts of both cesium-137 and cesium-134, which has a half-life of only two years. Any “naturally” occurring cesium-134 would be long gone.
Naturally, the oceans hold about 1-2 becquerels (Bq) of radioactivity per cubic meter of water, where a becquerel is one decay per second. The researchers found hundreds to thousands of times more, with up to 3,900 Bq per cubic meter in areas closer to the shore, and 325 Bq in sites as far as 372 miles (600 km) away.
Currents and Eddies
Ocean phenomena, big and small, also affected the radiation spread. For instance, the team found that the Kuroshio Current, which runs roughly east-northeast from the south of Japan toward the Aleutians, acts as a kind of boundary for the spread of radioactive material, even as it also pushes a lot of it away from the coast. In addition, eddy currents that arise at the edge of the Kuroshio caused the cesium and other radioactive pollutants to reach higher concentrations in some places closer to the coast, carrying some of the drifters toward populated areas south of Fukushima.
“It’s [an] interesting thing to think about, as the concentrations vary by a factor of 3,000,” Buesseler said. “With what we knew about transport prior to this work, you wouldn’t know why it is so different.”
The team also looked at the amounts of cesium isotopes in the local sea life, including zooplankton, copepods (tiny crustaceans), shrimp and fish. They found both cesium-137 and cesium-134 in the animals, sometimes at concentrations hundreds of times that of the surrounding water. Average radioactivity was about 10 to 15 Bq per kilogram, depending on whether it was zooplankton or fish (concentrations were lowest in the fish). [Image Gallery: Freaky Fish]
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. And while cesium was present in the fish, it doesn’t accumulate up the food chain the way polychlorinated biphenyls (PCBs) or mercury do. Mercury and PCBs tend to stay in an animal’s tissues for long periods, so when a tuna eats smaller fish, it takes in all the chemicals those small fish have eaten. Cesium tends to be excreted from animals much faster.
The WHOI expedition calculated that some 1.9 petabecquerels – or 1.9 million billion becquerels total – were in the stretch of ocean studied. The total released by the Fukushima accident was much greater, but a lot of the radionuclides were dispersed by the time of the sampling in June.
The researchers also found silver-110, but it wasn’t clear that was from the Fukushima plant. Another set of experiments measured strontium-90 levels, but that work hasn’t been published yet.
Kara Lavender Law, an oceanographer at the Sea Education Association, noted this kind of work is important because the picture of how ocean currents affect environmental pollutants isn’t always clear. “From an ocean-current standpoint we know what large-scale circulation is like, but when you get into where contaminant spills will end up, sometimes the picture is a whole lot different when you look at smaller areas,” Law told LiveScience.