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How Fukushima’s radioactive fallout in Tokyo was concealed from the public

Because of the controversy surrounding Satoshi’s paper and the lack of research on the health impacts of these particles, it remains unclear to what extent Tokyo residents have been exposed to dangerous radiation levels as a result of the Fukushima accident.

Because CsMPs are so small, typically two microns or less in diameter, if humans breathe them, they could potentially reach the bottom of the lung, and be lodged into sacs known as alveoli, where the lung generally cannot expel them.

By unit of mass, CsMPs are much more radioactive than even spent reactor fuel

Japanese radiochemist Satoshi Utsunomiya found that air samples from March 15, 2011, in Tokyo contained a very high concentration of insoluble cesium microparticles. He immediately realized the implications of the findings for public safety, but his study was kept from publication for years.

Bulletin, By François Diaz-Maurin, January 13, 2025 [excellent illustrations]

On March 14 and 15, 2011—three days after the Great East Japan Earthquake and its resulting tsunami hit the Fukushima nuclear power plant—explosions at two of the plant’s reactor buildings released a huge amount of invisible radioactivity. These radioactive plumes were blown away by the wind, descending over the surrounding area and into the ocean. Eventually, the radiation emitted from the Fukushima plants spread over the entire Northern Hemisphere. It also spread to Japan’s capital, Tokyo.

Following the explosions, Japanese researchers rushed to collect and study radioactive materials from the soil and the air to find out what had happened inside the reactors, believed now to have melted down because their cooling systems failed. On March 13, the Tokyo Metropolitan Industrial Technology Research Institute, the agency responsible for measuring the air quality of particulate matter in the Tokyo area, started to collect air samples more frequently. This effort was part of the Tokyo metropolitan government’s emergency monitoring program for environmental radiation, which aimed to detect gamma-emitting nuclides in airborne dust. The filters revealed that at around 10 a.m. on March 15, 2011, a large plume of radioactivity reached Tokyo, some 240 kilometers (149 miles) south of Fukushima. All samples taken on March 14 and March 15 showed spikes in radioactivity.

The institute’s researchers published their first results in the journal of the Japan Radioisotope Association in June 2011 (Nagakawa et al. 2011); they estimated the total exposure dose to humans from radioactive substances, including iodine 131 and cesium 137 found in airborne dust, foodstuffs, and drinking water from the Setagaya ward in the old Tokyo City. Extrapolating from their measurements from March 13 to May 31, they calculated the corresponding annual cumulative dose of radiation in that part of Tokyo as being 425.1 microsieverts, which is less than half the annual dose limit to the public recommended by the International Commission on Radiological Protection. In a second conference publication in English (Nagakawa et al. 2012), the researchers extended their monitoring period to October and estimated that the total annual effective dose due to inhalation for adults in the Tokyo metropolitan area from the Fukushima radioactive plumes was far lower, at 25 microsieverts.

But two years after the accident, Japanese scientists discovered a new type of highly radioactive microparticle in the exclusion zone around the Fukushima plant. The microparticles, which had been ejected from the Fukushima reactors, contained extremely high concentrations of cesium 137—a radioactive element that can cause burns, acute radiation sickness, and even death. Satoshi Utsunomiya, an environmental radiochemist from Kyushu University in southwestern Japan, soon found that these particles were also present in air filter samples collected in Tokyo in the aftermath of the Fukushima accident.

The controversy surrounding his attempts to publish his findings nearly cost him his career and prevented his results from being widely known by the Japanese public ahead of the 2020 Summer Olympics in Tokyo.[1] Scientists still don’t know if these highly radioactive microparticles present significant danger to people, and Satoshi is one of the very few scientists who is focused on trying to find out. “We have the measurements now that tell that the particles did pass over population centers and were being deposited in places,” Gareth Law, a radiochemist from the University of Helsinki, told me. “We should answer the question.”

The discovery

In May 2012, Toshihiko Ohnuki, an accomplished environmental radiochemist then at the Japan Atomic Energy Agency (JAEA), visited Yoshiyasu Nagakawa at the Tokyo Metropolitan Industrial Technology Research Institute, also known as TIRI. Nagakawa was the first author of two TIRI studies on radiation exposure in Tokyo, and Ohnuki asked Nagakawa if he could obtain some air samples for further analysis. Ohnuki had already studied how radioactive cesium fallout from Fukushima reacted with components of contaminated soil. Now, he wanted to do the same with the airborne dust samples from Tokyo.

Nagakawa gave Ohnuki five small filters that had been collected from the Setagaya ward in old Tokyo City at different times on March 15, 2011—the day the radioactive plume reached Tokyo. Ohnuki received the samples without restriction on their use, and no written agreement was made.[2]

Back in his laboratory at JAEA, Ohnuki performed autoradiography of the five samples, revealing many radioactive spots on all of them. The bulk radioactivity on each sample was measured to be between 300 counts per minute for the filter that covered the midnight to 7 a.m. period and 10,500 counts per minute between 10 a.m. and 11 a.m. on March 15.[3] The radiation rate was so high that Ohnuki had to cut some of the filters into small pieces, less than one square centimeter, to keep from saturating the scanning electron microscope. Ohnuki stored the unexamined filters for future analysis.

Months later, in August 2013, four researchers from the Meteorological Research Institute in Japan reported for the first time about a new type of spherical radioactive cesium-bearing particle that had been ejected in the early days of the Fukushima accident (Adachi et al. 2013). The researchers had collected air samples on quartz fiber filters at their institute in Tsukuba, located 170 kilometers southwest of the Fukushima plant. Their findings, published in Scientific Reports, were about to revolutionize the way environmental radiochemists understood the radioactive fallout from Fukushima.

Back in the lab, the researchers placed the filters on an imaging plate and inserted them into a portable radiography scanner. The images revealed many black dots, which indicated the presence of radioactive materials on the filters, with a maximum radioactivity level measured on the sample at 9:10 a.m. on March 15, 2011, four days after the Fukushima accident began. The researchers placed this sample under a scanning electron microscope and then into an energy-dispersive X-ray spectrometer to directly observe the shape and composition of the radioactive materials on the filters. What they saw stunned them………………………………………………………………

Shocking results

The newly discovered entities were initially called spherical cesium-bearing particles, but Satoshi and his co-workers coined the term cesium-rich microparticles, or CsMPs, in 2017, which is now what researchers call them generally (Furuki et al. 2017). CsMPs had not been noted in earlier major reactor accidents.

Scientists knew the microparticles came from the Fukushima reactors because their isotopic ratio between cesium 134 and cesium 137 matched the average ratio for the three damaged reactors calculated by the Oak Ridge National Laboratory.[5] Because these particles emanated from the Fukushima reactors, Satoshi and the other scientists studying them thought that they may contain evidence about reactions that occurred during the accident. But the environmental radiochemist’s curiosity was also triggered by the unique features of these microparticles: Their size is very small, typically two to three microns, even smaller than one micron in some cases.[6] And the cesium concentration in each of the particles is very high relative to their size.

After Satoshi obtained four small pieces of the Tokyo air filters, he designed what he calls “a very simple procedure” to find out whether the filters contained cesium-rich microparticles. In April 2015, he took autoradiograph images of the four pieces, confirming what Ohnuki had already seen with a digital microscope at JAEA. Then Satoshi moved to characterize the structural and chemical properties of the particles using scanning electron microscopy (SEM) and atomic-resolution transmission electron microscopy (TEM). Although the procedure’s design was simple, executing these steps would prove to be extremely difficult.

In July 2015, as Satoshi was busy working on the Tokyo air filters in his lab at Kyushu University, Ohnuki received a note from Nagakawa, the TIRI researcher who had provided the samples, asking him to return them so they could be reanalyzed. In his e-mail, Nagakawa did not specify the motive for his request, which appeared innocuous: “Please return at least some of the materials we gave you for reanalysis … if the location is unknown, it can’t be helped.”

Ohnuki immediately sent Nagakawa two filters from March 15, including the filter from 10 a.m. to 11 a.m. that had the highest level of radioactivity and contained the largest number of radioactive spots. Ohnuki added that he had discarded the other three filters after he analyzed them in 2013.

Nagakawa also asked Ohnuki whether he was planning to publish papers based on the samples. Ohnuki explained that he stopped analyzing them after his inconclusive attempts in 2013, but did not mention he had given Satoshi part of the filters for study.[9]

Satoshi was now ready to publish his results in a scientific journal. These were important findings that the scientific community needed to know. But Satoshi also understood that they could create a public relations crisis in Japan because his findings contradicted previous statements that played down the implications for public health of Fukushima fallout in Tokyo.

The Goldschmidt Conference—the foremost such international meeting on geochemistry—that year was held in the Japanese city of Yokohama. Satoshi was invited to give a plenary talk and present his research on environmental contamination from the Fukushima disaster (Utsunomiya 2016). During the talk, he presented his new findings on the Tokyo air filters. His talk received a lot of attention and was even reported by several Japanese and international newspapers. After his presentation, the scientific chair of the conference, Hisayoshi Yurimoto, said: “Very interesting results. And also very shocking results.”[1

In April and June 2016, Satoshi conducted dissolution experiments and quickly confirmed that the CsMPs were insoluble in water. The experiments also showed that most of the cesium activity on these filters came from CsMPs. In fact, up to 90 percent of the cesium radioactivity came from these microparticles, not from soluble forms of cesium—meaning that most of the cesium radioactivity detected during the March 15 plume in Tokyo was from CsMPs.

Between 2016 and 2019, a Kafkaesque sequence of events circled about Ohnuki, the former JAEA researcher who gave Satoshi the Tokyo air filter samples, and Satoshi. During that sequence of events, Satoshi’s research paper was accepted for publication by a prestigious scientific journal after peer review—but the journal delayed publication of the paper for years, eventually deciding not to publish it based on mysterious accusations of misconduct that, it turned out, were unwarranted. As a result, Satoshi’s findings were not made widely known, saving the Japanese authorities a possible public relations crisis as the summer Olympics in Tokyo neared. Because of the controversy surrounding Satoshi’s paper and the lack of research on the health impacts of these particles, it remains unclear to what extent Tokyo residents have been exposed to dangerous radiation levels as a result of the Fukushima accident.

I worked to reconstruct the sequence of events related to Satoshi’s research paper to find out whether the controversy over its publication was the result of some unethical practice on his part; competition between research laboratories; or attempted suppression of scientific results. The account that follows is based on the review of dozens of e-mails, letters, reports, and transcripts of phone conversations the Bulletin has obtained, as well as on multiple interviews with people directly involved in the events.

In August 2016, the leader of Nagakawa’s research group at TIRI, Noboru Sakurai, sent an e-mail to Ohnuki urging him to return filter samples he had earlier obtained from TIRI to the Tokyo Institute of Technology, where Ohnuki was now employed. Ohnuki responded that the filters had already been sent, but Sakurai maintained they had not received them. Ohnuki had asked a staff member of the research group he used to work in at the Japan Atomic Energy Agency to send the samples he had left there, but the samples were not sent. Because the samples were studied in a controlled area, theymay have been disposed of together with other Fukushima-related samples that had been stored at JAEA.

In October, as Ohnuki dealt with insistent requests that he return the filter samples, Satoshi submitted two research manuscripts to the journal Scientific Reports, one on the first successful isotopic analysis of individual cesium-rich microparticles based on soil samples collected from the exclusion zone at Fukushima, and one on the first characterization of the CsMPs from the Tokyo air filter samples that he had presented during his talk in Yokohama. Both articles were accepted in early January 2017 after peer review.[11]

The Tokyo paper, titled “Caesium fallout in Tokyo on 15th March, 2011 is dominated by highly radioactive, caesium-rich microparticles,” was co-authored by three graduate students from Satoshi’s lab—Jumpei Imoto, Genki Furuki, and Asumi Ochiai, who conducted the experiments—and three Japanese collaborators: Shinya Yamasaki from the University of Tsukuba who contributed to the measurement of samples; Kenji Nanba of Fukushima University, who contributed to the collection of samples; and Toshihiko Ohnuki, who had obtained the samples. The paper included two international collaborators who were world experts in the study of radioactive materials, Bernd Grambow of the French National Center for Scientific Research at the University of Nantes in France and Rodney C. Ewing of Stanford University, who contributed to the research ideas and participated in the analysis of the data. Satoshi was the lead author of the study.

……………………………………………..On the day of the visit, Moriguchi sent an e-mail to Ohnuki, pressing him to inform TIRI about the planned publication. “This type of information makes government agencies very sensitive,” Moriguchi wrote. “If the results obtained from these valuable sample collections conducted at a research institute under the administration were to incur the displeasure of government agencies and it becomes difficult to obtain cooperation from research institutions, we are concerned that this could hinder future research using these types of samples.”

…………………………………………………..Almost immediately, Sakurai moved to block the publication, according to e-mails obtained by the Bulletin.

………………………………………………………………………………………In July 2017, TIRI increased the pressure by sending a formal complaint to the Tokyo Institute of Technology, where Ohnuki was now employed. In a letter that the researchers were not able to see until a year after it was sent, TIRI accused Ohnuki of “suspected acts violating internal regulations, researcher’s ethics and code of conduct” in providing Satoshi with samples from TIRI without the institute’s consent.

As the issue became more political and involved more institutions, Satoshi continued his research on CsMPs and presented two other papers about Fukushima at the next Goldschmidt Conference in Paris in August 2017. Later that month, under pressure from the Tokyo Metropolitan Institute of Industrial Technology, the Tokyo Institute of Technology opened a formal investigation of Ohnuki on suspicion of improper research activities with Satoshi. “It was like a court,” Satoshi said of being called before the compliance committee. Except that, unlike in a trial, he did not know the exact terms of what they were accused of. “The team at TIRI didn’t even allow Kyushu University to show me this letter,” Satoshi said. “So at that point, I didn’t understand what the problem was.”

………………………………………………………………………………………………………………………………………………. Cleared but still harassed

During the investigation, Satoshi almost gave up on publishing the paper based on examination of the filters in Tokyo. He told the committee members that he would probably withdraw the paper, then “in press,” from Scientific Reports. Both the committee members and TIRI were pleased. “But then I talked to Rod [Ewing], and we did something clever,” Satoshi explained. They would not withdraw the paper; instead, they would keep it “in press” until the investigation was over.

…………………………………………………………………………….Tokyo Tech initiated a pressure campaign against Ohnuki and Satoshi to get the samples back…………………………………..

Satoshi did not want to give the samples away. “These are the only evidence to prove our article,” he said.

………………………………………………………“I sent all the samples to Stanford,” Satoshi said. Satoshi sent the air filter samples through regular postal services “in a UPS package.”[15] On September 13, Kyushu University’s executive vice president, Koji Inoue, called Satoshi to his office and yelled at him, urging him to give back the samples. Satoshi told Inoue that it was too late; he had already sent the samples to Stanford “for further investigation.”

Now the samples were secured, but Satoshi still needed his paper to be published.

……………………………………………………………………….. Thompson’s article in Scientific American was published on March 11, 2019, mentioning the fact that the paper had been rejected (Thompson 2019).

In June 2019, Satoshi and his co-authors posted their paper on arXiv (Utsunomiya et al. 2019), thereby making the findings public—two-and-a-half years after its acceptance by Scientific Reports. Ohnuki’s name does not appear in the list of co-authors on the arXiv paper, and Satoshi did not acknowledge TIRI for providing the samples.

……………………………………………………………………………………. After the paper was made public, the researchers received some attention, but not the visibility commensurate with the implications that the study had for public health in Japan.[16] The three institutions—TIRI, Tokyo Tech, and Kyushu University—were all “very happy,” Satoshi said. “People may think that we lost, but for me, we actually protected science.“

New risks

In the early days after the Fukushima accident, radiochemists thought that the situation was very different from Chernobyl. The three reactor-core damage events at Fukushima were considered to be of low energy, meaning that no actual explosion of the reactors had occurred, as was the case for Chernobyl. This led radiochemists to assume that radioactive particles probably had not come out of the reactors or, at least, not in large volume. A lot of the early post-accident research, therefore, focused on the traditional environmental radiochemist approach of collecting soils and sediments, doing bulk analysis, and learning from that.

It was only after scientists discovered the existence of cesium-rich microparticles that researchers, including Satoshi, realized that particles had actually been ejected from the reactors.

…………………………………………………………………………Because they were unknown until recently, CsMPs pose new risks that are still underappreciated by the research community and public authorities.

Once formed, radioactive cesium 137 has a half-life of about 30 years, after which half of the nuclides will have decayed into stable barium 137, whereas the other half will remain radioactive. CsMPs tend to accumulate, forming hotspots that contain many of the particles.[17] Hotspots of the microparticles have been found inside and outside abandoned buildings in the Fukushima exclusion zone and in other places (Fueda et al. 2023; Ikenoue et al. 2021; Utsunomiya 2024a). “They’re actually there in great numbers in many places, and then that’s when the health questions start to come in,” Law said. Despite their great numbers and potential risks, hotspots of CsMPs have not been systematically mapped around Fukushima. “When we visited the exclusion zone, we could still see some hot spot occurrences on the roadside without any protection,” Satoshi said. “We shouldn’t be able to access freely that kind of hot spots.”

Because CsMPs are so small, typically two microns or less in diameter, if humans breathe them, they could potentially reach the bottom of the lung, and be lodged into sacs known as alveoli, where the lung generally cannot expel them.[18] Scientists don’t know what would happen then. For instance, a typical immune system response would consist of some kind of clearance mechanism that seeks out foreign bodies and tries to either envelop or dissolve them. But it is still unknown how exactly CsMPs would dissolve in lung fluids.

Most knowledge about breathing and radioactive particulates is based on the assumption that particles dissolve, and researchers have calculated the rates for their dissolution in the human body. But because CsMPs don’t dissolve easily, once inhaled, they will likely stay longer in the human body. Researchers believe that, because CsMPs are so slow to dissolve, they may stay much longer—certainly for several months, maybe longer—in the body, compared to hours or days for suspended cesium.[19]

By unit of mass, CsMPs are much more radioactive than even spent reactor fuel. Some researchers from the Japan Atomic Energy Agency have shown that cultured cells exposed to the radiation from suspended CsMPs display a stronger local impact compared to what is known from previous radiological simulation studies using soluble radionuclides (Matsuya et al. 2022). Scientists are only now seeing some emerging evidence that the point-source nature of the radioactivity from CsMPs could lead to damage to cell systems. This is qualitatively different from the conventional estimate of internal radiation dose at the organ level based on uniform exposure to soluble cesium.

Despite the new risks that CsMPs might pose, the study of their impacts has received little interest.

…………………………………………………………………………………………………….Satoshi continues to study CsMPs actively and regularly presents his results to the Goldschmidt Conference and publishes his results in scientific journals. He and his collaborators work relentlessly to understand better the fate of CsMPs in the environment and their impacts on human health. In 2024, Satoshi received the Geochemical Society’s Clair C. Patterson Award in recognition of his innovative contributions to the understanding of CsMPs.[21]……………… more https://thebulletin.org/premium/2025-01/how-fukushimas-radioactive-fallout-in-tokyo-was-concealed-from-the-public/?utm_source=SocialShare&utm_medium=Facebook&utm_campaign=Facebook&utm_term&fbclid=IwY2xjawHyUndleHRuA2FlbQIxMQABHb1H3gK2UVzfBC5I7-s75EVtx4t5Q9uUi2MspvTqpluEOqbarYJJnhIwUA_aem_ok6x3HQOxccGg2I-7KnZjA

January 14, 2025 - Posted by Christina Macpherson | Japan, radiation, secrets,lies and civil liberties