Radiation doses underestimated in study of city in Fukushima

understimated radiation Date jan 9 2019.jpg
Workers decontaminate land in Date, Fukushima Prefecture, in 2013.
January 9, 2019
A nuclear physicist who has drawn attention for tweeting about fallout from the Fukushima nuclear disaster has admitted that he and a colleague underestimated radiation doses in an article for an international scientific journal.
Ryugo Hayano, professor emeritus at the University of Tokyo, said the error, which he recognized on Jan. 8, was “unintentional.”
The article, carried in the Journal of Radiological Protection’s online edition in July 2017, listed average radiation doses that were one-third of the actual levels for people in Date, a city around 60 kilometers northwest of the crippled Fukushima No. 1 nuclear plant, he said.
Hayano’s admission came after an atomic nucleus expert contacted the journal last year to point out unnatural data carried in the report and call for a correction.
The radiation doses in the article were based on figures kept by Date residents after the nuclear accident unfolded in March 2011.
“Even if residents lived in the most contaminated area of Date for 70 years, the median of the doses would not exceed 18 millisieverts,” the article concluded.
However, Shinichi Kurokawa, professor emeritus with the High Energy Accelerator Research Organization, an institute jointly used by national universities, raised doubts about the data presented in some sections of the report.
When Hayano and his colleague re-examined the figures, they found that they mistook a monthly dose recorded on a dosimeter as the figure for three months of exposure.
Hayano said the conclusion of the report still stands.
“Even after the error was fixed, I believe the average of annual doses will be within the 1-millisievert mark,” he said.
The benchmark upper limit for radiation exposure among ordinary people is 1 millisievert a year.
Hayano has frequently tweeted about radiation levels and doses from the nuclear disaster.
He was also involved in another research paper that analyzed radiation doses among people in Date. Kurokawa also questioned the veracity of a chart in the second report.
The second report has often been cited in discussions by the government’s Radiation Council on setting standards for protecting people from radiation.
The two research papers were produced after the Date city government provided Hayano’s research team with data on radiation doses of about 59,000 residents.
But it has emerged that data for 27,000 citizens were provided without their consent.
The city plans to set up an investigation panel to find out why it occurred.
Date has a population of 61,000.

Town that hosts disaster-hit Fukushima nuclear plant aims to allow daytime access to special zone in 2020

Futaba in Fukushima Prefecture, where restrictions may be lifted to allow daytime access in 2020, is seen in November
December 13, 2018
FUKUSHIMA – One of the municipalities that hosts the crisis-hit Fukushima No. 1 nuclear plant is considering lifting restrictions on daytime access in spring 2020 to an area being rebuilt in the town center, sources close to the matter said Thursday.
The town of Futaba, Fukushima Prefecture, where units Nos. 5 and 6 of the complex are located, became a ghost town after the 2011 disaster due to high levels of radiation. Those wishing to visit need to apply in advance for permission to enter and must pass through a checkpoint.
But such restrictions would be lifted during the daytime for access to a special zone several kilometers from the Fukushima plant on the Pacific coast, where government-funded decontamination and reconstruction work is underway, with the aim of evacuees returning in the spring of 2022.
To lift the restrictions, the town will have to meet government criteria to be unveiled by the end of the year. If realized, the move will pave the way for the town to be rebuilt.
After the massive earthquake and tsunami triggered the world’s worst nuclear catastrophe since the 1986 Chernobyl disaster, the whole of Futaba was designated a no-go zone for residents, with radiation levels exceeding 50 millisieverts per year.
The town’s plan to mark the special zone as a reconstruction hub was endorsed by the central government in September last year. The town said at the time that in most of the area radiation levels had fallen below 20 mSv per year, with figures around Futaba Station brought down below 5 mSv per year.
Decontamination work has been conducted to make sure radiation levels will be below 20 mSv per year throughout the special zone by the spring of 2020. The government eventually aims to lower the levels below 1 mSv per year.
The International Commission on Radiological Protection sets radiation exposure under normal situations at 1 mSv per year and says 100 mSv of exposure over a lifetime would increase the possibility of developing cancer by up to 1 percent.
Under emergency situations, the ICRP sets a limit of 20-100 mSv of annual radiation exposure.
In the special zone, which will occupy about 560 hectares, or 10 percent of the town, residential areas and commercial facilities will be built. Futaba envisions some 2,000 residents will eventually live in the area.
With more residents and construction workers expected to come to the area, the town is likely to discuss measures with the central government to beef up surveillance through the use of security cameras or patrols.
Five other municipalities near the Fukushima No. 1 plant aim to build similar reconstruction hubs for the return of their own evacuees.
All six municipalities are planning to have evacuation orders lifted in the hub zones by the spring of 2023 but Futaba is the first to announce plans for free access during daytime.
The Fukushima No. 1 plant spewed a massive amount of radioactive materials after a magnitude 9.0 earthquake triggered tsunami that flooded the facility on March 11, 2011.
Reactor Nos. 1 to 3 suffered fuel meltdowns, while hydrogen explosions damaged the buildings housing units Nos. 1, 3 and 4. Reactor Nos. 5 and 6 achieved a cold shutdown after several days.
The disaster left more than 18,000 people dead or missing. As of November, more than 54,000 people were still unable to return to their homes.

Fukushima sake shop opens in New York

Plainly criminal. Taking advantage of the unknowing American public and at the same time using such sales as propaganda in Japan telling to the Japanese public that it is safe, look even the Americans buy it. 
December 2, 2018
The Fukushima government has opened a sake shop in New York specializing in brews from the prefecture.
The shop opened its doors on Saturday inside a commercial facility in Manhattan. Officials from the prefecture and the facility celebrated the occasion.
Sake sales are booming in the United States. Exports to the US have increased 50 percent in the past 10 years.
Sakes brewed in Fukushima Prefecture have performed well in competitions. The shop offers 50 brands from 11 breweries.
One customer said he’s tasted Japanese sake several times before, but none were as good as the one he tried in the shop. He said he would like to visit Fukushima someday.
A Fukushima tourism official said breweries in the prefecture are having a hard time finding buyers since the 2011 disaster. He said he hopes the shop will boost the image of Fukushima’s sakes worldwide.
The shop will operate until March next year.

Abe, IOC chief to visit Fukushima venue for 2020 Olympics



November 5, 2018
TOKYO – Prime Minister Shinzo Abe and International Olympic Committee President Thomas Bach plan to visit the venue in Fukushima for the 2020 Tokyo Olympics later this month, a government source said Sunday.
With a “reconstruction Olympics” being one of the fundamental themes of the Summer Games, the government hopes the visit planned for Nov 24 will increase momentum toward the recovery of the country’s northeastern region, devastated by the 2011 earthquake, tsunami and ensuing crisis at the Fukushima Daiichi nuclear power plant.
Bach will visit Japan to attend a two-day general assembly meeting of the Association of National Olympic Committees starting Nov 28, followed by an IOC Executive Board session, both to be held in Tokyo.
The Olympic torch relay will start in Fukushima Prefecture on March 26, 2020, with the flame scheduled to be lit in the ancient Greek city of Olympia on March 12 the same year, a day after the ninth anniversary of the 2011 disaster.
The city of Fukushima will host six softball games including a match played by the Japan team on July 22 as the first event of the Olympic Games.

Temporal changes in 137Cs concentrations in fish, sediments, and seawater off Fukushima Japan

Demersal fish live and feed on or near the bottom of seas or lakes (the demersal zone). They occupy the sea floors and lake beds, which usually consist of mud, sand, gravel or rocks. In coastal waters they are found on or near the continental shelf, and in deep waters they are found on or near the continental slope or along the continental rise. They are not generally found in the deepest waters, such as abyssal depths or on the abyssal plain, but they can be found around seamounts and islands. The word demersal comes from the Latin demergere, which means to sink.
Demersal fish consist of Benthic fish and benthopelagic fish, they are bottom feeders. They can be contrasted with pelagic fish which live and feed away from the bottom in the open water column. Demersal fish fillets contain little fish oil (one to four percent), whereas pelagic fish can contain up to 30 percent.[not verified in body]
Benthic fish, sometimes called groundfish, are denser than water, so they can rest on the sea floor. They either lie-and-wait as ambush predators, maybe covering themselves with sand or otherwise camouflaging themselves, or move actively over the bottom in search for food. Benthic fish which can bury themselves include dragonets, flatfish and stingrays.
Benthopelagic fish inhabit the water just above the bottom, feeding on benthos and zooplankton. Most demersal fish are benthopelagic.
October 15, 2018
We analyzed publicly-available data of Fukushima 137Cs concentrations in coastal fish, in surface and bottom waters, and in surface marine sediments and found that within the first year of the accident pelagic fish lost 137Cs at much faster rates (mean of ~1.3% d-1) than benthic fish (mean of ~0.1% d-1), with benthopelagic fish having intermediate loss rates (mean of ~0.2% d-1). The loss rates of 137Cs in benthic fish were more comparable to the decline of 137Cs concentrations in sediments (0.03% d-1), and the declines in pelagic fish were more comparable to the declines in seawater. Retention patterns of 137Cs in pelagic fish were comparable to that in laboratory studies of fish in which there were no sustained 137Cs sources, whereas the benthopelagic and benthic fish species retained 137Cs to a greater extent, consistent with the idea that there is a sustained additional 137Cs source for these fish. These field data, based on 13,511 data points in which 137Cs was above the detection limit, are consistent with conclusions from laboratory experiments that demonstrate that benthic fish can acquire 137Cs from sediments, primarily through benthic invertebrates that contribute to the diet of these fish.

Japan recognizes first death related to Fukushima cleanup

September 7, 2018
The Japanese government has recognized the first death associated with cleanup work at the Fukushima Daiichi nuclear power plant after the tsunami disaster in March 2011, according to the Ministry of Health, Labour and Welfare.
The government designated the death of an unnamed man in his 50s as an “industrial accident.” The man, who had worked at the plant from 1980 to 2015, was diagnosed with lung cancer in February 2016.
After the 2011 tsunami that was triggered by a 9.0-magnitude earthquake, the man was assigned to “radiation control” work in which he was responsible for monitoring radiation levels and work time of cleanup crews.
The Ministry of Health, Labour and Welfare recognized his cancer and death as related to his work at the plant. A committee of experts determined his accumulated radiation level exceeded government standards.
Kunihiko Konagamitsu of the ministry said 17 workers had applied to be considered cases with an “industrial accident” designation, including three with leukemia and one with thyroid cancer. Two workers withdrew their requests, five were dismissed, and five are still under review.
The March 11, 2011, quake was the worst to hit Japan and lasted nearly six minutes. More than 20,000 people died or went missing in the earthquake and tsunami that followed.
Three reactors at the Fukushima Daiichi nuclear plant, operated by Tokyo Electric Power Co. or TEPCO, melted down in the nation’s worst nuclear disaster. The damaged reactors released radioactive materials into the air and more than 100,000 people were evacuated from the area. Forty-five thousand workers were involved in the ensuing cleanup.
In 2015 Japan health officials confirmed the first case of cancer linked to cleanup work at the plant.
In 2016, TEPCO said that decommissioning the reactor was like climbing a mountain and that it could take as long as 40 years.

Fukushima unrecognized threat of radioactive microparticles


Fukushima Microparticles, An Unrecognized Threat

In the years since the initial disaster there have been disparities between the official radiation exposure estimates and the subsequent health problems in Japan. In some cases the estimates were based on faulty or limited early data. Where a better understanding of the exposure levels is known there still remained an anomaly in some of the health problems vs. the exposure dose. Rapid onset cancers also caused concern. The missing piece of the puzzle may be insoluble microparticles from the damaged reactors.
What are microparticles ?
These microscopic bits of fuel and other materials from the reactor meltdowns have been found around Japan since soon after the disaster. Citizens with hand held radiation meters first discovered them as highly radioactive fine black sands on roadsides and gutters. These substances eventually caught the attention of researchers who determined they are tiny fused particles of vaporized reactor fuel, meltdown byproducts, structural components of the reactors and sometimes concrete from the reactor containments. The Fukushima microparticles are similar to “fuel fleas” or “hot particles“. Hot particles or fuel fleas have been found at operating nuclear reactors that had damaged fuel assemblies. These fused particles found around Japan are different in that they are a byproduct of the reactor meltdowns.
The small size of these microparticles, smaller than 114 μm makes them an inhalation risk. Other studies have also confirmed the size is small enough to inhale. These microparticles have been found near Fukushima Daiichi, in the evacuation zone, outside of the evacuation zone and as far away as Tokyo.
How microparticles were created at Fukushima Daiichi
The heat of the meltdown processes reached temperatures high enough to cause the nuclear fuel and other materials to break down into small particles. The uranium in the fuel further oxidized and then volatilized once temperatures reached 1900K. As these materials broke down into nanoparticle sized components of the fuel melt process, this set up the conditions for them to condense.  As these materials cooled the fused microparticles were created. Newer studies call these microparticles “CsMPs” (Cesium bearing micro particles).  A 2018 study of how these microparticles were created gives a plain language explanation of the process. https://pubs.acs.org/doi/pdf/10.1021/acs.est.7b06309
“From these data, part of the process that the FDNPP fuels experienced during the meltdown can be summarized as the follows: Cooling waters vaporized, and the steam reacted with Zr and Fe forming their oxides after the loss of power to the cooling system. UO2, which is the main composition of fuels, partially oxidized and volatilized at greater than ∼1900 K. (9,10) The fuel assemblies melted unevenly with relatively less irradiated fuels being heated to a higher temperature as compared with the high burnup fuels and volatilized as evidenced by the 235U/238U isotopic ratio.(9) The fuel assembly collapsed and moved to the bottom of RPV. The temperature increased locally to at least greater than 2400 K based on the liquidus temperature of U−Zr oxides. Locally formed oxides melted to a heterogeneous composition, including a small amount of Fe oxides,(27) which then became a source of Fe−U single crystals and U−Zr-oxide eutectic phases. Specifically, euhedral magnetite nanocrystals encapsulated euhedral uraninite nanocrystals, which would have crystallized slowly at this stage. Liquid U−Zr-oxide nanodroplets were rapidly cooled and solidified to a cubic structure. When the molten fuels hit the concrete pedestal of the PCV, SiO gas was generated at the interfaces between the melted core and concrete and instantly condensed to form CsMPs.(5) The U−Zr-oxide nanoparticles or the magnetite nanocrystals subsequently formed aggregates with CsMPs. Finally, the reactor debris fragments were released to the environment along with CsMPs.”
The microparticles may have left the reactors through multiple processes including containment leaks,  containment venting operations, hydrogen explosions and the later reduction and addition of water in an attempt to control the molten fuel.
New study looks at how to quantify these substances
A new study found a useful way to quantify how much of the contamination in an area is due to microparticles (hot particles). By using autoradiography they were able to confirm the number of microparticles in a sample. Soil samples near Fukushima Daiichi ranged from 48–318 microparticles per gram.  The microparticles had high concentrations of radioactive cesiums, in the range of ∼1011 Bq/g. The study stresses the health concern that these microparticles pose due to cellular damage from the highly concentrated radiation level. The authors also mention the risk re-suspension of microparticles in the air poses to the public.
Not just cesiums
A separate study found strontium-90 in the Fukushima microparticles at a ratio similar to what has been found in contaminated soil samples. This study included the amount of hot particles (aka: microparticles) found in soil samples taken in the fallout zone in Fukushima north-west of the plant. They ranged from 0-18 microparticles per square meter of soil. This information confirms that strontium-90 is part of some of these fused microparticles. https://academic.oup.com/jrr/advance-article/doi/10.1093/jrr/rry063/5074550
An ongoing research project and paper by Marco Kaltofen documents these hot particles further. In the 2017 paper they found more than 300 such hot particles from Fukushima Daiichi in Japanese samples.  A hot particle was found in a vacuum cleaner bag from Nagoya, over 300 km from the disaster site. https://www.sciencedirect.com/science/article/pii/S0048969717317953?via%3Dihub
“300 individual radioactively-hot particles were identified in samples from Japan; composed of 1% or more of the elements cesium, americium, radium, polonium, thorium, tellurium, or strontium. Some particles reached specific activities in the MBq μg− 1 level and higher.”
The study found americium 241 in two house dust samples from Tokyo and in one from Sendai, 100 km north of the disaster site.  The sample set collected in 2016 showed a similar instance of highly radioactive hot particles compared to the 2011 samples. This appears to show that the threat from these reactor ejected hot particles has not gone away. A majority of the collected samples were from locations declared decontaminated by the national government.
The above graph is from the 2017 Kaltofen paper. These represent the highest readings for cesium found in their microparticle samples. The highest in the graph is Namie black sand. These black sand substances found around Fukushima prefecture and as far south as Tokyo were discovered to be largely made up of ejected reactor materials based on multiple studies.
The 2018 study we cited earlier in this report to explain the microparticle creation process also confirms some of these microparticles also contain radioactive isotopes of uranium. This further confirms the creation of some of these microparticles from the fuel itself. Uranium poses a particular concern due to the extremely long half lives involved.
How these act differently in the environment
In the case of the microparticles that contained Strontium 90, the isotope would normally move with water in the environment. Due to the insolubility of the microparticles, the strontium 90 stays in the top soils. Studies on microparticles predominantly carrying radioactive cesiums showed that the radioactive substances did not migrate through the environment as expected.
Microparticles were found in road gutters, sediment that collected in parking lots, below downspouts and similar places where sediments could concentrate. These initial discoveries hint at how the microparticles could migrate through the environment. The findings of the 2017 Kaltofen study indicate that microparticles can persist years later, even in places that were decontaminated. This may be due to the natural processes that have caused many areas to recontaminate after being cleaned up. There has been no effort to clean up forest areas in Japan. Doing so was found to be extremely difficult. The forest runoff may be one method of recontamination.
The risk to humans and animals
The subject of hot particles and the risk that they might pose to human or animal health has been controversial in recent years. Some studies found increased risks, others claimed a lesser risk from these substances. One study we reviewed may have discovered the nuances of when these substances are more damaging.
Most studies on hot particles aimed to determine if they were more damaging than that of a uniform radiation exposure to the same body part. A 1988 study by Hoffman et. al. found that hot particle damage varied by the radiation level of the particle, distance to nearby cells and the movement of the particle within the tissue. A high radiation particle might kill all the nearby cells but cause transformation in cells further away. Those dead cells near the hot particle would stimulate the transformed cells to reproduce faster to replace the dead cells. https://academic.oup.com/rpd/article-abstract/22/3/149/161256
A hot particle of moderate radiation would cause more transformations than cell death of nearby cells. High radiation hot particles that moved around in the organ, in this case the lung, would cause the most transformations. These acted like multiple moderate radiation hot particles transforming cells as they moved around. Those transformations are what can turn into cancers. This study’s findings appear to explain the results found in other studies where fewer cancers were found than they expected in certain groups.
A veteran who was exposed during US atomic testing had experience over 300 basal cell carcinomas. The study concluded that the skin cancers in atomic veterans could be induced by their radiation exposure. Continued exposure to ultraviolet radiation then promoted those cancers.
Other studies found damage in animal models. A study of hot particles on pig skin showed roughly half of the exposures caused small skin lesions. Two in the higher exposure group caused infections, one of these resulted in a systemic infection. https://inis.iaea.org/collection/NCLCollectionStore/_Public/28/061/28061202.pdf
A mouse study where hot particles were implanted into the skin found increased cancers of the skin. https://www.tandfonline.com/doi/abs/10.1080/09553009314550501
Workers at Fukushima Daiichi in the group with some of the highest radiation exposures were discovered to have these insoluble microparticles lodged in their lungs. When the workers radiation levels didn’t decrease as expected, further tests were done. Scans found the bulk of the worker’s body contamination was in their lungs. The lung contamination persisted on subsequent scans. The looming concern is that these microparticles in the lungs can not be ejected by the body.
Risks have been known for decades 
The US NRC issued an information notice related to a series of hot particle exposures at nuclear plants where workers were exposed beyond legal limits. https://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1987/in87039.html
Damaged fuel was the source in all cases. Even improperly laundered protective clothing was found to be a risk factor. Contaminated clothing from one facility could make it through the laundry process with a hot particle undetected on bulk scans of finished laundry. This would then result in an exposure to a different worker at a different plant who donned the contaminated gear. The hot particles when in contact with skin can give a high dose rate. Plants with even small fuel assembly leaks saw significant increases in worker exposure levels.
“In addition to any increased risk of cancer, large doses to the skin from hot particles also may produce observable effects such as reddening, hardening, peeling, or ulceration of the skin immediately around the particle. “
These problems are thought to only occur in high dose exposures from hot particles. One worker in the review had an estimated 512 rem radiation exposure from a hot particle.  Workers at US nuclear power plants are subjected to strict screening programs when they exit or return to work. This increases the chance of detecting and removing a hot particle before it can do more damage. This also lessens the potential for one to leave the plant site. The general public exposed to a nuclear plant disaster does not receive this level of scrutiny.
How this risk may have played out in Fukushima
Soon after the reactor explosions ripped through Fukushima Daiichi, people in the region began complaining of nosebleeds and flu like symptoms. These eventually began being reported as far south as Chiba and Tokyo.  https://www.aljazeera.com/indepth/features/2011/08/201181665921711896.html
The government responded that these complaints were “hysteria” or people trying to scare others. These problems were so widespread and coming from diverse people it had seemed to be a significant sign in the events that unfolded.
On March 21, 2011 there was rain in Tokyo that may have washed out contamination still being ejected at the plant. Events at Daiichi between March 17-21 caused increased radiation releases.
In 2013 there was an unusual uptick in complaints about severe nosebleeds. This happened at the time typhoon Man-yi made landfall in Tokyo. The bulk of the people who responded to a survey by a foreign policy expert working in the office of a member of Japan’s Diet were from the Kanto region (Tokyo) where the typhoon made landfall.
Children in the Fukushima region that were found to have thyroid problems also complained of frequent nosebleeds and skin rashes.  People have described unusual ongoing health problems such as this woman in Minami Soma near Fukushima Daiichi who had odd rashes, a rapid loss of teeth etc.  Cattle housed 14 km from the disaster site have shown with white spots all over their hides, something previously seen after US nuclear tests. https://www.huffingtonpost.com/evaggelos-vallianatos/the-nuclear-meltdown-at-f_b_4209766.html
The USS Reagan was offshore of Fukushima Daiichi March 11 to 14th. Plume maps for iodine 131 (a gaseous release from the meltdowns) blew in the wind north and at times east out to sea during those dates. These same winds could have carried microparticles out to sea. A number of sailors on the Reagan and those working with the rescue helicopters have fallen ill. Eight have died since the disaster. This newer account of the events on the Reagan raise even more concerns about what happened to those trying to save people after the tsunami.
Namie Mayor, Tamotsu Baba resigned his office in June 2018 after a year of off and on hospitalization. He had been undergoing treatment for gastric cancer. He died a few weeks after resigning. His cancer may have predated the disaster, but in the last year his health drastically declined. Namie is in the area of some of the highest fallout from the disaster.
Fukushima plant manager Masao Yoshida died of esophageal cancer in 2013. TEPCO insisted his cancer was not related to the disaster due to the rapid onset. This is a common claim around cancers that could be tied to Fukushima, yet the number of cancers soon after the disaster has been hard to ignore.
As we neared completion of this report the labor ministry announced that the lung cancer death of a Fukushima Daiichi worker was tied to his work during the disaster. The worker was at the plant during the early months of the disaster and worked there until 2015. TEPCO didn’t give specifics of his work role, only mentioning he took radiation levels. TEPCO mentioned that the worker wore a “full face mask respirator” during his work. All of the workers at Daiichi wore the same after ordered to do so after meltdowns were underway. The worker was not among the highest exposure bracket so he may not have been receiving detailed health monitoring. Radiation exposure monitoring during the early months of the disaster was inconsistent and sometimes missed exposures. https://mainichi.jp/english/articles/20180905/p2a/00m/0na/004000c
What microparticles change about the disaster
Highly radioactive microparticles were released to the environment during the meltdowns, explosions and subsequent processes in units 1-3 at Fukushima Daiichi.
Microparticles have been found near the disaster site, in the evacuation zone, far outside of the evacuation zone and south into the Tokyo region. These substances persist in the environment and have been found in areas previously decontaminated.
These microparticles significantly change the exposure estimates for the general public. Individual exposures can not be accurately estimated by the use of generic environmental radiation levels as this does not account for the individual’s exposure to microparticles.
Microparticle exposure has multiple variables that create a unique level of risk to the exposed human or animal. They can in the right circumstances cause significant damage to nearby tissues, persist in the body, cause damage, initiate or promote a cancer.
Microparticle exposures may be the missing puzzle piece that explains a number of odd problems tied to the Fukushima disaster. Health problems that showed up soon after the disaster. Exposed populations with aggressive or sudden cancers and other serious health problems that can be created or exacerbated by radiation exposure.
Microparticles continue to pose a public health risk in some parts of Japan that experienced fallout and increased radiation levels due to the disaster.