Volume 60, Issue 12 p. 2357-2358
Letters to the Editor
Free Access

Depopulation with Rapid Aging in Minamisoma City After the Fukushima Daiichi Nuclear Power Plant Accident

Kazunobu Ishikawa MD

Kazunobu Ishikawa MD

Center for Medical Education and Career Development, Fukushima Medical University, Fukushima, Japan

Department of Cardiology, Fukushima Medical University Hospital, Fukushima, Japan

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Yukio Kanazawa MD

Yukio Kanazawa MD

Department of Gastrointestinal Medicine, Minamisoma Municipal General Hospital, Minamisoma, Japan

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Shigeto Morimoto MD

Shigeto Morimoto MD

Department of Geriatric Medicine, Kanazawa Medical University, Kahoku-gun, Japan

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Takashi Takahashi MD

Takashi Takahashi MD

Laboratory of Infectious Diseases, Graduate School of Infection Control Sciences, Kitasato University, Minato-ku, Japan

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First published: 11 December 2012
Citations: 20
To the Editor:

On March 11, 2011, a strong earthquake (magnitude 9.0) occurred off the Pacific coast and hit the northeast of Japan, followed by devastating tsunamis, which destroyed many coastal cities.1, 2 The three operating reactors at Fukushima Daiichi nuclear power plant shut down automatically just after this earthquake,3 but 41 minutes later, a massive wall of rolling water burst through the plant's defenses and inundated the reactor buildings. The tsunami flooded emergency generators, leaving the plant without power for cooling systems while radioactive decay kept heating the cores. In the control room, plant workers desperately tried to run crucial instruments, using torches and car batteries scavenged from nearby vehicles, but the last line of emergency systems failed, and the three reactors melted down several days later. This process induced release of hydrogen gas, which caused explosions in the reactor buildings.

People in Fukushima mistrust the actions of the government and the Tokyo Electric Power Company because of poor provision of accurate information concerning the plant accident, even 1 year and 4 months after the disaster. Volatile radioactive chemicals including iodine-131 and cesium-137 started to spread into the air and sea. Investigation of radionuclide was conducted on bamboo sampled from six sites within a 25- to 980-km radius of the Fukushima plant in July to August 2011.4 Strikingly high concentrations of radiocesium-134 and -137 activity were detected in mature leaves from Fukushima city (65 km from the Fukushima plant), in excess of 71 and 79 kBq/kg of dry weight (DW). In Kashiwa city (195 km from the plant), sample concentrations were in excess of 3.4 and 4.3 kBq/kg DW. In Toyohashi city (440 km from the plant), concentrations were below the measurable limits of up to 4.5 Bq/kg DW.

Last summer, a comprehensive public health study was established with a large budget at Fukushima Medical University.3 This investigation was designed to follow up on the health of some 2 million people in the region for 30 years. According to the latest data (February 20, 2012), 99.3% of 9,747 people living in towns or villages close to the plant received an accumulated effective dose of less than 10 mSv during the first 4 months after the accident. The highest dose was 23 mSv, well below the acute exposure level (100 mSv) related to a slight increase in risk of malignant diseases. In Minamisoma, there were 305 disaster-associated deaths, 298 (97.7%) of which were in elderly adults.

Minamisoma Municipal General Hospital, which is located in the evacuation area 20 km from the plant, has served as a regional core institute for evacuees. Medical care providers have been performing health monitoring and medical care, including vaccination programs, for more than 4,000 victims.

In April 2012, the government released newly revised guidelines regarding the evacuation zones from the plant, but wide-area evacuation still continues in Fukushima. The population of 72,000 in Minamisoma before the accident decreased to approximately 10,000 just after the accident. On March 29, 2012, it had recovered to approximately 45,000. The proportion of those aged 65 and older increased from 25.9% to 32.1% (Figure 1A). In addition, the retention rate of population according to age group has dramatically changed (Figure 1B). Many younger than 40, especially infants, children, and young parents, moved out of the communities because of fear regarding radiation exposure, causing a rapid increase in the proportion of elderly people. In addition, loss of ordinary lifestyle may inhibit activities of daily living of older adults. Elderly adults dislike moving, and many continued to live there, suggesting the breakup of communities and families. The average age of the population in Minamisoma has increased by 14 years because of the nuclear disaster, with younger people leaving, whereas older people have stayed behind, reaching the level that it had been estimated it would reach by 2025. Similar events have been observed in Futaba county and Iitate village near Minamisoma.

Details are in the caption following the image
(A) Age-dependent decrease in population in Minamisoma city after the Great East Japan Earthquake and Fukushima Daiichi nuclear power plant accident. (B) Retention rate of population according to age group. Population data in Minamisoma on March 29, 2012 were compared with those on March 1, 2011.

Public attention for the nuclear plant workers5 and people living in Fukushima is fading rapidly. We should continue to pay attention to depopulation with rapid aging, which may make rebuilding populations in stricken areas difficult.

Acknowledgments

Conflict of Interest: None of the authors has any financial disclosure to report.

Author Contributions: Ishikawa K. and Morimoto S.: Study concept and design. Kanazawa Y.: Acquisition of data. Ishikawa K.: Analysis and interpretation of data. Ishikawa K. and Takahashi T.: Preparation and writing of the letter.

Sponsor's Role: None.