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Masaharu Tsubokura went from providing routine health care to giving lectures and visiting classrooms.

Masaharu Tsubokura

This physician has studied the Fukushima disaster for a decade—and found a surprising health threat

One evening in June 2011, Masaharu Tsubokura went to bed and found he couldn’t close his left eye. His face was paralyzed, and for a few weeks the doctor who had spent months counseling residents displaced by a massive nuclear disaster was himself a patient.

The paralysis was temporary. But the stress that caused it has been a constant in Tsubokura’s life since he volunteered in Japan’s Fukushima prefecture, days after the triple catastrophe that rocked it on 11 March 2011: a magnitude 9 earthquake, a tsunami that rose up to 40 meters, and multiple meltdowns and explosions at the Fukushima Daiichi Nuclear Power Plant. What was meant to be a short volunteer stint giving health checks to evacuees became a career that has lasted 10 years and counting.

In the months after the disaster, Tsubokura moved from routine medicine to measuring radiation exposure. He became adept at explaining radiation basics and risks to residents and officials. “He spent a huge amount of time in town hall meetings, lectures, and dialogues with local people, which made him respected and trusted,” says Kenji Shibuya, a global health scholar at King’s College London who collaborated with him. And Tsubokura soon reached a controversial conclusion: The evacuation had a far bigger impact on health than the radiation. “No one died of radiation,” he says, whereas uprooting tens of thousands of people caused clear social and health problems.

Early on, Tsubokura did his best to allay fears among evacuees and residents living just outside the evacuation zone. Many people welcomed his reassurances, though some accused him of being an apologist for the power company and the government. But the physician, now 39, persisted.

“Many people would have left and said, ‘OK, I tried my best,’” says Gilles Hériard-Dubreuil, a Paris-based consultant involved in community rehabilitation in Belarus after the Chernobyl nuclear plant accident in Ukraine in 1986. It’s a sign of Tsubokura’s courage and humanity, he says, “that he maintained his presence and he faced the adversity.”

Splitting his time between jobs at hospitals in Tokyo and Fukushima, Tsubokura accumulated data that would put the risks in perspective. In more than 140 papers, he and colleagues have documented the relatively low radiation exposure of Fukushima residents and the health impacts of the evacuation—a high death toll among the elderly, increases in chronic diseases, and a decline in general well-being. That perspective is likely to be valuable in the future, says Masahiro Kami, a physician who was Tsubokura’s medicine Ph.D. adviser and heads a nonprofit that strives to improve medical practice in Japan. “A Fukushima-like accident will happen again in China or somewhere in the world,” Kami says.

Fearing radiation from the damaged reactors, masked residents evacuate nearby Minamisōma on 17 March 2011.

The Asahi Shimbun via Getty Images

Tsubokura seized “a unique opportunity to study health effects following a nuclear accident,” adds Mikhail Balonov, a radiation health specialist at the Research Institute of Radiation Hygiene in St. Petersburg, Russia. High radiation after the Chernobyl accident made its health effects hard to separate from the social and psychological impacts of displacement. But the lower radiation levels at Fukushima allowed Tsubokura to isolate the impacts of the evacuation in his studies, which he mostly financed himself.

“My goal was to help the local people, not as a researcher but as a local physician,” Tsubokura says. He wrote papers “to share the knowledge with the scientific community.” But another motivation, he says, “was to record how the disaster affected people [as a way to] give my condolences.”

Tsubokura’s Fukushima odyssey began, improbably, in Paris, where he attended a medical meeting in April 2011, less than 1 month after the disaster.

He and his girlfriend were aboard one of the iconic sightseeing barges that ply the Seine, gliding past the stately Parisian facades, when his cellphone rang. Kami was calling from Tokyo, explaining that physicians were urgently needed. He asked whether Tsubokura could volunteer in Hamadōri—a local name for Fukushima prefecture’s coastal region.

Kami says he had confidence Tsubokura was a good fit. The region needed hands-on clinicians, preferably young and adaptable, who could work well with the overwhelmed local physicians struggling to provide basic care. Even while he was a medical undergraduate student, Tsubokura’s focus on patients had impressed Kami, one of his professors. Many medical scientists “treat patients as if they are material for research,” Kami says; but for Tsubokura, patients came first and research followed.

An Osaka native, Tsubokura had never been to Fukushima. “My first reaction was, ‘What’s Hamadōri?’” he says. An internet search back at the hotel set him straight: Kami was summoning him to the heart of the disaster. Tsubokura’s girlfriend was furious that he might put himself in danger. It would be just a couple of weeks, he recalls promising.

When Tsubokura arrived in the Fukushima city of Minamisōma in late April 2011, Japan was still counting the victims. The earthquake and tsunami had devastated more than 800 kilometers of coastline, leaving 15,899 dead, 2527 missing, and 500,000 homeless. And a nebulous peril had been unleashed: Swamped by the tsunami, the Fukushima Daiichi plant had suffered explosions and meltdowns that released an estimated 538.1 petabecquerels of radioactivity into the atmosphere.

That amount was about one-tenth of the estimated radiation release in Chernobyl. But it inflicted further trauma on the people of the region. Fearing more radiation releases, the government ordered the evacuation of everyone within 20 kilometers of the plant and under a plume of radiation that poked like a finger toward the northwest. Many more people, living beyond the 20-kilometer line, left voluntarily. Eventually more than 160,000 fled, most within a week or two of the accident. Evacuees crammed into schools, gyms, and other public buildings in cities outside the evacuation zones for several months until emergency housing was built. Some people chose to bunk with relatives.

Evacuations driven by radiation concerns added to the thousands of people who packed into temporary shelters after the Fukushima earthquake and tsunami.

Athit Perawongmetha/Getty Images

As Tsubokura visited evacuation centers scattered across Fukushima, checking on residents’ health, he heard one overriding concern: “What is radiation?” he was asked. “Is it OK for me to stay here? Is it OK for my children to go outside?” At first he explained radiation basics one on one, drawing on his experience in using radiation to treat leukemia. In early May, one mother asked him to talk to a group of her friends. Tsubokura worked up a PowerPoint presentation, explaining radiation basics and exposure levels in the region. Word got around, and he was soon giving public lectures in Minamisōma  and nearby towns.

“Many, many people came to the seminars and asked a lot of questions,” he says. His message was often reassuring, telling people outside the evacuation zone that their radiation exposure was likely very low. Although Tsubokura explained the risks and urged residents to make their own decisions, some people accused him of being a government agent intent on minimizing the hazards. The stress and grueling schedule likely contributed to his temporary facial paralysis.

Eventually Tsubokura learned to take hostile questions in stride. At one meeting in Sendai in 2015, Hériard-Dubreuil recalls some audience members grilling Tsubokura, asking: “Are you on the side of the NGOs [nongovernmental organizations]? Are you on the side of the government?” He says Tsubokura answered, “I’m on the side of the people.”

Hard data on the radiation risks were scarce, however, so Tsubokura and colleagues set out to change that. Fukushima residents feared they were breathing in radioactive particles and eating contaminated food, major sources of internal radiation exposure after the Chernobyl accident. Minamisōma General Hospital acquired a whole-body radiation counter and launched Fukushima’s first radiation screening program in early July 2011. “The phone rang all day” when the hospital started to take reservations, Tsubokura says. Soon, every time slot available for months was filled.

To his relief, “the numbers were really low,” he says. Meanwhile, authorities bolstered radiation monitoring of the environment and gave residents dosimeters. Tsubokura went back to his lectures better equipped to answer specific questions.

Demand for his presentations picked up in late 2011 and early 2012 as families with children considered returning to the voluntarily evacuated areas ahead of the 1 April start of the new school year. “It was crazy; he was giving lectures day and night,” says Sachiko Bamba, a Minamisōma resident whose Veteran Mothers Society support group arranged venues and printed flyers.

With his boyish demeanor and unruly mop of tousled hair, Tsubokura had a particular rapport with children. “Instead of a one-way presentation of information, he started by asking the children to tell him what they were worried about,” Bamba says. Questions centered on such daily conundrums as whether laundry hung out to dry would get contaminated and the safety of well water. One student asked whether hugging a cat that had played outside carried a risk of radiation exposure. Bamba recalls Tsubokura making a humorous nod to the Japanese custom of removing shoes at the door and saying, “Cats don’t wear shoes, so it may be a good idea to wipe its paws when you bring a cat into the house.”

Under a cloud

More than 160,000 people were initially evacuated within a 20-kilometer radius of the damaged power station and to the northwest of Fukushima. Many have returned.

Evacuationorder lifted Closed to habitationindefinitely FukushimaDaiichi NuclearPower Plant 20-kilometerevacuationradius Minamisōma Iitate Namie Katsurao Nahara Kawa-mata Futaba Tamura Kawauchi Ōkuma Tomioka
(Map) K. Franklin/Science; (Data) Nippon.com

The Veteran Mothers gathered the material from Tsubokura’s lectures to create an illustrated pamphlet; the 10,000 copies sold out in the blink of an eye, Bamba says. There were two more printings, and volunteers even created an English version so residents could reassure overseas friends. Tsubokura convinced many “that it is OK for us to live here,” Bamba says.

Takako Watanabe was among the believers. Her Minamisōma home was outside the mandatory evacuation zone, but concerns for her then-9-year-old daughter, Misaki, led them to move in with Watanabe’s uncle in neighboring Ibaraki prefecture. She took Misaki back to Minamisōma when schools reopened in late April 2011. But alarmed by “talk of radiation making young girls unable to bear children,” the two evacuated again during the school’s summer break. As the 2012 school year approached, Misaki increasingly missed her Minamisōma classmates. Watanabe attended several of Tsubokura’s presentations. “His easy-to-follow explanations were a relief to hear,” she says, and she and Misaki returned to Minamisōma for good.

Not everyone was convinced. Mizue Kanno, an evacuee from the town of Namie, still doubts that the whole-body counters accurately measured internal exposure. Tsubokura “seems to have worked on behalf of the country and TEPCO,” she says, referring to the Tokyo Electric Power Co., owner of Fukushima Daiichi. Kanno, who cannot return home because of lingering radiation in Namie, had a friend who died of leukemia, one of five leukemia victims from the same village. And despite official assurances to the contrary, she believes the incidence of cancer has risen in the Fukushima region. “Did the nuclear accident really cause no health damage?” she asks.

Tsubokura has come to believe it did—but indirectly. Scores of the region’s medical personnel—doctors, nurses, technicians, and clerical and support staff—evacuated either under order or voluntarily, often fearing how radiation would affect their young children. In a retrospective study, Tsubokura and colleagues found that hospitals in Minamisōma were working with just half their normal staff during the first month after the disaster, when they were still dealing with earthquake and tsunami injuries and trying to evacuate bedridden patients. Even after 18 months, staffing was 15% less than before the accident, and Tsubokura believes the weakened health care system had grim consequences.

In that first month, “the risk of death rose in both genders and every age group,” Tsubokura wrote in a 2018 review article in the Journal of the National Institute of Public Health. The impact was most notable among the elderly living in long-term care facilities. Tsubokura and colleagues found that among 715 residents of five evacuated Minamisōma nursing homes, the relative risk of death was 2.7 times higher than before the disaster. At one facility, 25% of residents evacuated died within 90 days. The most common cause of death was pneumonia, suggesting “they died as a result of weakness, a decrease in care, and the general deterioration of their physical condition, and not from the onset of any particular disease,” Tsubokura wrote.

Other health impacts emerged. Akihiko Ozaki, a breast cancer surgeon and frequent Tsubokura collaborator, found that after the disaster the lag between when women recognized possible breast cancer symptoms and when they saw a doctor grew, resulting in more advanced cancer and more difficult treatment. And Tsubokura found that the incidence of diabetes in Minamisōma and nearby Sōma increased by 5% over 3 years, and diabetes-related complications such as stroke became more common and severe. Tsubokura and colleagues blame changes in exercise habits and diet, as well as disrupted familial and community ties. The social stresses “led people to pay less attention to their own health,” Ozaki says.

Yuji Onuma visits his hometown of Futaba in 2020, nearly 10 years after evacuating. The town, 4 kilometers from the Fukushima nuclear plant, is still off-limits for habitation.

Reuters/Issei Kato

The findings all suggest that, in Fukushima, those stresses were the real health threat. Evacuation after a nuclear accident may be unavoidable, Tsubokura says. Still, he believes waiting until temporary housing and other facilities are ready could sometimes save lives. “Tsubokura’s findings can be, to some extent, used for the modification of evacuation paradigms,” Balonov says.

Some experts think the hazards of radiation are too poorly understood to warrant a less cautious approach. “Radiation exposure from this accident was not at a level that would cause acute injury,” says Hideyuki Ban, secretary-general of the antinuclear Citizens’ Nuclear Information Center in Tokyo. But low-level exposure could still lead to a cancer increase years later, he says. “Delayed effects of radiation exposure should be avoided, and evacuation orders are put in place for that purpose.”

Hériard-Dubreuil says Tsubokura’s more important lesson may be for communities recovering from disruptions of all kinds. Tsubokura’s efforts to give the public reliable information and explain risks empowered people “to become, again, the actors in their own lives,” Hériard-Dubreuil says.

Tsubokura’s Fukushima work teaches other kinds of lessons, his admirers say. His studies there have ranged far beyond his hematology background, something “very unusual for Japanese M.D.s,” who tend to stick to the clinical specialty they studied in medical school, says Shibuya, formerly on the faculty of the University of Tokyo. He adds that Tsubokura “had a broader social perspective from the beginning.”

He has become a mentor for younger doctors and researchers who share his social concerns. Ozaki is one example. He landed at Minamisōma General a few years out of medical school. Working with Tsubokura allowed him to explore “the role medical care plays in the bigger framework of society,” he says. Toyoaki Sawano, another surgeon, also moved to Minamisōma General in part to study the bullying of schoolchildren who evacuated to other prefectures and the health issues facing the legions of workers who decontaminated Fukushima’s landscape. “I don’t think I would have been on this path through life without meeting professor Tsubokura,” Sawano says.

U.S. student Claire Leppold was pursuing a master’s in public health at the University of Edinburgh when Tsubokura gave a presentation there in early 2015. “I was just blown away” by his research on indirect health impacts, she says. Leppold won a grant from Edinburgh to join the Minamisōma group studying a cohort of evacuees with diabetes. “I have been profoundly lucky to meet him,” says Leppold, now at the University of Melbourne.

Every Monday evening, Tsubokura and younger doctors from the region gather in a “Tsubokura study session” to discuss their research and trade tips on writing papers. Tsubokura says he is out to show his younger colleagues that those working in a rural area can still publish papers garnering international attention. When he thinks of his hematology colleagues from medical school, he says, “No one has published as many papers as I have; no one has been involved with public health issues like I have been.”

Today, evacuation orders have been lifted for many towns in the disaster region, and residents are returning. But there is more to do in Fukushima, Tsubokura says. In June 2020, he joined the faculty of Fukushima Medical University and became eligible for grants. With funding from Japan’s Nuclear Regulation Authority, he is pursuing several research efforts, including studying how medical and nursing care facilities within the evacuation zone handled bedridden patients. He is also discussing with local authorities how to stave off lifestyle diseases among the 37,000 Fukushima evacuees who still cannot return to their homes and communities. They remain off-limits because annual radiation doses remain at more than 50 millisieverts—more than 10 times the typical annual background radiation.

Tsubokura is well aware of how much of his life he has spent working near ground zero. The woman who objected to his initial sojourn in Fukushima married him despite his disregard for her concerns. But she often reminds him, he says, that “you said you will go to Minamisōma for a week, but it’s been 10 years.”