Makiko Orita

Determinants of the return to hometowns after the accident at Fukushima Dai-ichi nuclear power plant: a case study for the village of Kawauchi

The Great East Japan Earthquake in March 2011 destroyed the Fukushima Dai-ichi Nuclear Power Plant (FNPP) and almost all residents in a 20 km radius from the plant eventually evacuated. FNPP reactors were stabilised in December 2011; some evacuees decided to return to their hometowns, and the other evacuees remained. Efforts were made to identify the determinants that affect the decision to return home in order to promote recovery of the surrounding area of FNPP. Seventy-one residents who had not returned to hometown and 56 residents who had returned were selected. Logistic regression analysis adjusted for confounding factors showed that being female [odds ratio (OR): 2.43, p = 0.03], living in areas with relatively higher ambient doses (OR: 3.60, p=0.01) and expressing anxiety over radiation exposure (OR: 8.91, p < 0.01) were independently associated with decisions not to return. Results of this study suggest the importance of active participation by scientists and local authorities in communicating the risk to the general population involved in returning home.

Bipolarization of Risk Perception about the Health Effects of Radiation in Residents after the Accident at Fukushima Nuclear Power Plant.

The late health effects of low-dose rate radiation exposure are still a serious public concern in the Fukushima area even four years after the accident at Fukushima Daiichi Nuclear Power Plant (FNPP). To clarify the factors associated with residents’ risk perception of radiation exposure and consequent health effects, we conducted a survey among residents of Kawauchi village in May and June 2014, which is located within 30 km of FNPP. 85 of 285 residents (29.8%) answered that acute radiation syndrome might develop in residents after the accident, 154 (54.0%) residents responded that they had anxieties about the health effects of radiation on children, and 140 (49.1%) residents indicated that they had anxieties about the health effects of radiation on offspring. Furthermore, 107 (37.5%) residents answered that they had concerns about health effects that would appear in the general population simply by living in an environment with a 0.23 μSv per hour ambient dose for one year, 149 (52.2%) residents reported that they were reluctant to eat locally produced foods, and 164 (57.5%) residents believed that adverse health effects would occur in the general population by eating 100 Bq per kg of mushrooms every day for one year. The present study shows that a marked bipolarization of the risk perception about the health effects of radiation among residents could have a major impact on social well-being after the accident at FNPP.

Evaluation of environmental contamination and estimated exposure doses after residents return home in Kawauchi Village, Fukushima Prefecture.

The external and internal exposure doses due to artificial radionuclides after the return of residents to their homes in Kawauchi Village, Fukushima Prefecture, including the restricted area within a 20-km radius from the Fukushima Dai-ichi Nuclear Power Plant (FNPP), were evaluated by gamma spectrometry of the soils and local agricultural products. The prevalent dose-forming artificial radionuclides from all samples were determined to be (134)Cs and (137)Cs (radiocesium). The estimated external effective doses from soils sampled on December 24 and 25, 2012 were 0.0017-9.2 mSv/y in the areas within a 20- to 30-km radius from the FNPP and 0.39-1.3 mSv/y in the areas within a 20-km radius from the FNPP. These levels appeared to be decreasing, despite the distance from the FNPP (median: 0.21 (0.012-0.56) mSv/y), compared to the levels just before the return of the residents to their homes on December 19 and 20, 2011 (median: 0.85 (0.40-1.4) mSv/y). The committed effective doses from the local agricultural samples in Kawauchi Village from May 1, 2012 to March 31, 2013 were sufficiently low, in the range of 18-44 μSv/y for males and 20-48 μSv/y for females (the range was 18-48 μSv/y for children and 25-43 μSv/y for adults), compared to the public dose limit (1 mSv/y, ICRP, 1991), although the potential for radiation exposure still exists. Residents who have not yet returned may be able to return to their homes with a long-term follow-up of environmental monitoring and countermeasures to reduce unnecessary radiation exposure.

Radiocesium concentrations in wild mushrooms collected in Kawauchi Village after the accident at the Fukushima Daiichi Nuclear Power Plant

It is well known from the experience after the 1986 accident at the Chernobyl Nuclear Power Plant that radiocesium tends to concentrate in wild mushrooms. In this study, we collected wild mushrooms from the Kawauchi Village of Fukushima Prefecture, located within 30 km of the Fukushima Daiichi Nuclear Power Plant, and evaluated their radiocesium concentrations to estimate the risk of internal radiation exposure in local residents. We found that radioactive cesium exceeding 100 Bq/kg was detected in 125 of 154 mushrooms (81.2%). We calculated committed effective doses based on 6,278 g per year (age > 20 years, 17.2 g/day), the average intake of Japanese citizens, ranging from doses of 0.11–1.60 mSv, respectively. Although committed effective doses are limited even if residents eat contaminated foods several times, we believe that comprehensive risk-communication based on the results of the radiocesium measurements of food, water, and soil is necessary for the recovery of Fukushima after this nuclear disaster.

Radiation and risk of thyroid cancer: Fukushima and Chernobyl.

30 years have passed since the accident at the Chernobyl nuclear power plant in Ukraine, and 5 years have passed since the crisis at the Fukushima Daiichi nuclear power plant. After the Chernobyl disaster, a significant increase in thyroid cancer was reported among children and adolescents exposed to radioactive iodine released at the time of the accident in Belarus, Russia, and the Ukraine. On the basis of the experience of Chernobyl, thyroid ultrasound examination is being done within the framework of the Fukushima Health Management Survey. This survey targets all residents who were younger than 18 years at the time of the Fukushima accident (roughly 360 000 individuals). The first screening cycle, done from October, 2011, to March, 2014, identifi ed 113 confi rmed or suspected thyroid malignancies among 300 476 screened individuals. The finding of thyroid cases after Fukushima might be an effect of screening caused by the use of modern, highly sensitive ultrasound technology. To examine this issue, the causal relation between radiation exposure and thyroid cancer in Fukushima should be carefully assessed against the existing evidence, especially from Chernobyl. In Chernobyl, mean thyroid doses of affected children were estimated to be 560 mSv [SD 1180] in Belarus and 770 mSv [260] in Ukraine. By contrast, doses of less than 15 mSv in 99% of children aged 0–14 years were reported in more than 1000 children from Fukushima after the accident. At these low levels, the Fukushima doses are unlikely to have caused a detectable excess in thyroid cancer within 4 years after possible exposure. Another important point to consider is the age of patients in the aftermath of the two accidents. In Belarus, according to the cancer registry established before the accident, 25 operated cases of thyroid cancer were reported during the fi rst 4 years after the accident (1986–89) in patients who were aged 0–15 years at exposure. This number rose to 431 in 1990–94, 766 in 1995–99, and 808 in 2000–03 (fi gure). In particular, starting from 1990, the incidence of thyroid cancer increased greatly in children who were aged 0–5 years at the time of the accident, which suggests that this age group is particularly vulnerable to the effects of radiation. The number of operated thyroid cancers after Chernobyl was the highest in the younger age groups, but only 4–10 years after the incident. On the basis of these observations from Chernobyl, the fi nding of large numbers of cases in older, and not younger, age groups after Fukushima is likely to be an eff ect of screening (fi gure). Sequential screenings in Fukushima should continue, and periodic comparisons should be done of patients’ age distribution against the prototypic radiation-induced patterns in Chernobyl.

Measurement of individual doses of radiation by personal dosimeter is important for the return of residents from evacuation order areas after nuclear disaster.

To confirm the availability of individual dose evaluation for the return of residents after the accident at the Fukushima Dai-ichi Nuclear Power Plant (FNPP), we evaluated individual doses of radiation as measured by personal dosimeters in residents who temporarily stayed in Evacuation Order Areas in Kawauchi village, which is partially located within a 20 km radius of the FNPP. We also compared individual doses with the external radiation doses estimated from the ambient dose rates and with doses estimated from the concentrations of radionuclides in the soil around each individual’s house. Individual doses were significantly correlated with the ambient doses in front of the entrances to the houses (r = 0.90, p<0.01), in the backyards (r = 0.41, p<0.01) and in the nearby fields (r = 0.80, p<0.01). The maximum cumulative ambient doses in the backyards and fields around the houses were 6.38 and 9.27 mSv/y, respectively. The maximum cumulative individual dose was 3.28 mSv/y, and the median and minimum doses were 1.35 and 0.71 mSv/y. The estimated external effective doses from concentrations of artificial radionuclides in soil samples ranged from 0.03 to 23.42 mSv/y. The individual doses were moderately correlated with external effective doses in the backyards (r = 0.38, p<0.01) and in the fields (r = 0.36, p<0.01); however, the individual doses were not significantly correlated with the external effective doses in front of the entrances (r = 0.01, p = 0.92). Our study confirmed that individual doses are low levels even in the evacuation order area in Kawauchi village, and external effective dose levels are certainly decreasing due to the decay of artificial radionuclides and the decontamination of contaminated soil. Long-term follow-up of individual doses as well as internal-exposure doses, environmental monitoring and reconstruction of infrastructure are needed so that residents may return to their hometowns after a nuclear disaster.

Communicating With Residents About Risks Following the Fukushima Nuclear Accident

The Fukushima nuclear accident in March 2011 posed major threats to public health. In response, medical professionals have tried to communicate the risks to residents. To investigate forms of risk communication and to share lessons learned, we reviewed medical professionals’ activities in Fukushima Prefecture from the prefectural level to the individual level: public communication through Fukushima Health Management Surveys, a Yorozu (“general”) health consultation project, communications of radiological conditions and health promotion in Iitate and Kawauchi villages, dialogues based on whole-body counter, and science communications through online media. The activities generally started with radiation risks, mainly through group-based discussions, but gradually shifted to face-to-face communications to address comprehensive health risks to individuals and well-being. The activities were intended to support residents’ decisions and to promote public health in a participatory manner. This article highlights the need for a systematic evaluation of ongoing risk communication practices, and a wider application of successful approaches for Fukushima recovery and for better preparedness for future disasters.

Internal Radiation Exposure Dose in Iwaki City, Fukushima Prefecture after the Accident at Fukushima Dai-ichi Nuclear Power Plant

As a result of the accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) on 11 March 2011, a huge amount of radionuclides, including radiocesium, was released and spread over a wide area of eastern Japan. Although three years have passed since the accident, residents around the FNPP are anxious about internal radiation exposure due to radiocesium. In this study, we screened internal radiation exposure doses in Iwaki city of Fukushima prefecture, using a whole-body counter. The first screening was conducted from October 2012 to February 2013, and the second screening was conducted from May to November 2013. Study participants were employees of ALPINE and their families who underwent examination. A total of 2,839 participants (1,366 men and 1,473 women, 1–86 years old) underwent the first screening, and 2,092 (1,022 men and 1,070 women, 1–86 years old) underwent the second screening. The results showed that 99% of subjects registered below 300 Bq per body in the first screening, and all subjects registered below 300 Bq per body in the second screening. The committed effective dose ranged from 0.01–0.06 mSv in the first screening and 0.01–0.02 mSv in the second screening. Long-term follow-up studies are needed to avoid unnecessary chronic internal exposure and to reduce anxiety among the residents by communicating radiation health risks.

Concentrations of Radiocesium in Local Foods Collected in Kawauchi Village after the Accident at the Fukushima Dai-ichi Nuclear Power Station

We evaluated the current concentrations of radiocesium in local foods collected in Kawauchi Village, which is located less than 30 km from Fukushima Daiichi Nuclear Power Station, to minimize public anxiety regarding internal radiation exposure through the consumption of locally produced foods after the 2011 Fukushima accident. The number of samples exceeding the regulatory radiocesium limit (100 Bq/kg for general foods) was five out of 4,080 vegetables (0.1%), 652 of 1,986 (32.8%) among edible wild plants and fungi, and eight of 647 (1.2%) in fruits. Our study confirmed that the internal radiation doses of ingesting these foods are acceptably low compared to the public dose limit, ranging from 24.4 to 42.7 μSv for males and from 21.7 to 43.4 μSv for females, although the potential for radiation exposure still exists. Long-term comprehensive follow-up should take place to clarify trends in radiocesium concentrations in local foods and the committed effective doses found in Fukushima-area residents. By constructing a system that allows residents to access information on radiocesium concentration in foods, a risk communication model between specialists and residents could be developed in the recovery phase after the Fukushima accident.

After Fukushima: Collaboration model

![Figure][1] Holding a bonsai plant grown while evacuated, a Kawauchi resident returns to his home. PHOTO: KYODO The March 2011 accident at the Fukushima Daiichi Nuclear Power Plant caused extensive human suffering and revealed the need for more effective means of communicating health risks