The Great East Japan Earthquake occurred on March 11, 2011. Fukushima Prefecture suffered immediate loss of life, including about 1600 confirmed dead and 224 people still missing. After the immediate consequences of the earthquake and tsunami, an additional 2333 “disaster-related deaths” were recorded due to evacuation.Reference Tsuboi, Sawano and Nonaka1 Notably, none of these deaths are attributable to radiation.
The Fukushima Prefectural Government commissioned Fukushima Medical University to conduct the “Fukushima Health Management Survey” (FHMS) to investigate long-term low-dose radiation exposure caused by the accident.Reference Yasumura, Hosoya and Yamashita2, Reference Yasumura, Ohira and Ishikawa3 The survey consists of a Basic Survey and 4 detailed surveys (Thyroid Ultrasound Examination, Comprehensive Health Check, Mental Health and Lifestyle Survey, and Pregnancy and Birth Survey). The primary purposes of this survey are to monitor the long-term health of Fukushima residents and to promote their health and well-being.
Subjects and Methods
The Basic survey aims to estimate the external radiation exposure doses of all Fukushima residents (about 2.06 million people). A self-report questionnaire was distributed with a request to reply by post.
Eligible participants of both the Comprehensive Health Check and Mental Health and Lifestyle Survey include all residents living in the evacuation zone of 13 municipalities specified by the national Government who have been at risk of negative evacuation effects. Comprehensive Health Check items vary across 3 age ranges to assess health and prevent lifestyle-related diseases. To provide adequate care for evacuees who are at a higher risk of developing mental health problems and lifestyle deterioration, self-report questionnaires are designed to be submitted by post or online. The survey items also vary according to age range, but mainly ask about current mental and physical status, lifestyle (diet, sleep, smoking, alcohol use, and exercise), etc. Parents of children aged 4-15 years are asked to evaluate their children using the Strength and Difficulties Questionnaire (SDQ).Reference Matsuishi, Nagano and Araki4 The K6 (Kessler Psychological Distress Scale) is self-administered for people aged 16 years or older and a cut-point of 13 was developed to operationalize the definition of serious mental illness, defined as meeting diagnostic criteria for a DSM-IV disorder in the past 12 months and experiencing significant impairment estimated to afflict US adults.Reference Kessler, Barker and Colpe5 We adopted 13 as a cut-point.
Moreover, we decided to provide Thyroid Ultrasound Examination to all Fukushima residents aged between 0 and 18 years as of March 11, 2011 because the Chernobyl accident revealed increased thyroid cancer in children exposed to radioiodine,Reference Brenner, Tronko and Hatch6, Reference Jacob, Bogdanova and Buglova7 and to address increased anxiety among parents.Reference Bromet, Goldgaber and Carlson8
Despite no significant increase in induced abortion or miscarriage observed after March 11, 2011,Reference Yasumura, Hosoya and Yamashita2 some pregnant women had been required to change clinics/hospitals and had received insufficient antenatal care. To alleviate their anxiety and provide them with necessary care, the Pregnancy and Birth Survey was started.
Results
About 467 000 Fukushima residents submitted Basic Survey questionnaires about their location and activities during the first 4 months after the accident. Responses came from about 27.7% of our population, of whom 99.8% received radiation doses less than 5 mSv.
The Comprehensive Health Check for those 15 years or younger showed that obesity rates have gradually improved from 2011 to 2015, but dyslipidemia (low HDL-C) has persisted after the Great East Japan Earthquake. Among those 16 years or older, the Comprehensive Health Check revealed that obesity, hypertension, dyslipidemia, diabetes, renal dysfunction, hyperuricemia, hepatic dysfunction, and polycythemia increased after the accident, but no findings implicate radiation effects.
The K6 Scale in Mental Health and Lifestyle Survey identified distress in 6.1% of respondents in 2021, higher than the 3.0% within the general Japanese population. Survey participants who evacuated from Fukushima and still live outside Fukushima showed higher K6 scores than those who evacuated from Fukushima and came back to live in Fukushima (Figure 1).
Figure 1. Trends in K6 score of 13 or higher, of Fukushima evacuees, by place of residence.
Source: 31st, 35th, 38th, 42nd, 45th, and 48th meetings of the Oversight Committee for the Fukushima Health Management Survey
The Thyroid Ultrasound Examination, as of July 2023, identified 316 cases of malignant or suspicious for malignancy lesions among 300 000 examinees.
There has been no change in the occurrence of preterm birth, low birth weight, or congenital anomalies among newborns in Fukushima Prefecture from fiscal year 2011 to fiscal year 2020. Furthermore, the proportions of these indicators have been lower than those of national data or general incidences in Japan.
Discussion
The Prefectural Oversight Committee mentioned that dose estimation results obtained from the Basic Survey were considered as “not being at a level where health effects can be confirmed with a statistical significance in light of the scientific knowledge obtained to date.”9
The Comprehensive Health Check for those 16 years or older revealed that some conditions increased after the accident, but no findings implicate radiation effects.9
The K6 Scale shows that it remains a matter of special concern that over double the national average still need support for depression or anxiety 10 years after the disaster, even though the proportion has decreased over the years. Why the K6 scores are different between those who live outside Fukushima and those who live inside Fukushima cannot be explained easily. Those who still live outside Fukushima may tend to fear the radiation to which they have already been exposed and/or have difficulty/unease about living in their own house. On the other hand, those who live inside Fukushima may tend to have less fear of radiation exposure effects in their daily lives. In the light of Search Activity (SA), which can be defined as personal activity aimed to change either the objective situation or the subject’s attitude toward it, those who giving up SA decreased bodily resistance, suppressed immunity, and predisposed subjects to the development of depression and maladaptive (neurotic) anxiety.Reference Socol, Vadim and Rotenberg10 Those who live outside Fukushima may tend to give up SA.Reference Socol, Vadim and Rotenberg10
The 21st Thyroid Examination Evaluation Subcommittee declared that analyses of estimated doses by UNSCEAR and findings among the thyroid examination participants showed no significant association and no dose-response relationship.11 Depending on this comment, the reason of detection of some amount of thyroid cancer is different from Chernobyl. The overdiagnosis as one of the important factors has been addressed.Reference Vaccarella and Silvia Franceschi12 It is difficult to differentiate the overdiagnosis cancer. We need to follow-up the eligible participants and analyze their data.
Based on results of the Pregnancy and Birth Survey, there have been no long-term effects of the post-disaster radiation accident on perinatal outcomes.Reference Kyozuka, Murata and Yasuda13
Conclusion
What problems have continued to the present day from the Fukushima nuclear accident? The answer will vary depending on a person’s position and/or way of thinking. I suspect that some of the problems arise from the misunderstanding of radiation health effects in Fukushima by non-Fukushima residents and the dignity of “place of living” among Fukushima residents.
Considering the present radiation dose in Fukushima excepting the designated evacuation zone, it is possible to live in Fukushima. The Fukushima Prefectural Government and Fukushima Medical University always support every Fukushima resident.
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