Evaluation of Environmental Contamination and Estimated Radiation Doses for the Return to Residents’ Homes in Kawauchi Village,Fukushima Prefecture

To evaluate the environmental contamination and radiation exposure dose rates due to artificial radionuclides in Kawauchi Village, Fukushima Prefecture, the restricted area within a 30-km radius from the Fukushima Dai-ichi Nuclear Power Plant (FNPP), the concentrations of artificial radionuclides in soil samples, tree needles, and mushrooms were analyzed by gamma spectrometry. Nine months have passed since samples were collected on December 19 and 20, 2011, 9 months after the FNPP accident, and the prevalent dose-forming artificial radionuclides from all samples were ¹³⁴Cs and ¹³⁷Cs. The estimated external effective doses from soil samples were 0.42–7.2 µSv/h (3.7–63.0 mSv/y) within the 20-km radius from FNPP and 0.0011–0.38 µSv/h (0.010–3.3 mSv/y) within the 20–30 km radius from FNPP. The present study revealed that current levels are sufficiently decreasing in Kawauchi Village, especially in areas within the 20- to 30-km radius from FNPP. Thus, residents may return their homes with long-term follow-up of the environmental monitoring and countermeasures such as decontamination and restrictions of the intake of foods for reducing unnecessary exposure. The case of Kawauchi Village will be the first model for the return to residents’ homes after the FNPP accident.     

Minimal Internal Radiation Exposure in Residents Living South of the Fukushima Daiichi Nuclear Power Plant Disaster

Following the Fukushima nuclear power plant disaster, assessment of internal radiation exposure was indispensable to predict radiation-related health threats to residents of neighboring areas. Although many evaluations of internal radiation in residents living north and west of the crippled Fukushima nuclear power plant are available, there is little information on residents living in areas south of the plant, which were similarly affected by radio-contamination from the disaster. To assess the internal radio-contamination in residents living in affected areas to the south of the plant or who were evacuated into Iwaki city, a whole body counter (WBC) screening program of internal radio-contamination was performed on visitors to the Jyoban hospital in Iwaki city, which experienced less contamination than southern areas adjacent to the nuclear plant. The study included 9,206 volunteer subjects, of whom 6,446 were schoolchildren aged 4–15 years. Measurements began one year after the incident and were carried out over the course of two years. Early in the screening period only two schoolchildren showed Cs-137 levels that were over the detection limit (250 Bq/body), although their Cs-134 levels were below the detection limit (220 Bq/body). Among the 2,760 adults tested, 35 (1.3%) had detectable internal radio-contamination, but only for Cs-137 (range: 250 Bq/body to 859 Bq/body), and not Cs-134. Of these 35 subjects, nearly all (34/35) showed elevated Cs-137 levels only during the first year of the screening. With the exception of potassium 40, no other radionuclides were detected during the screening period. The maximum annual effective dose calculated from the detected Cs-137 levels was 0.029 and 0.028 mSv/year for the schoolchildren and adults, respectively, which is far below the 1 mSv/year limit set by the government of Japan. Although the data for radiation exposure during the most critical first year after the incident are unavailable due to a lack of systemic measurements, the present results suggest that internal radio-contamination levels more than one year after the incident were minimal for residents living south of the crippled Fukushima nuclear plant, and that the annual additional effective doses derived from internal Cs contamination were negligible. Thus, internal radio-contamination of residents living in southern radio-contaminated areas appears to be generally well controlled.     

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.     

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.     

Removal Efficiency of Radioactive Cesium and Iodine Ions by a Flow-Type Apparatus Designed for Electrochemically Reduced Water Production

The Fukushima Daiichi Nuclear Power Plant accident on March 11, 2011 attracted people’s attention, with anxiety over possible radiation hazards. Immediate and long-term concerns are around protection from external and internal exposure by the liberated radionuclides. In particular, residents living in the affected regions are most concerned about ingesting contaminated foodstuffs, including drinking water. Efficient removal of radionuclides from rainwater and drinking water has been reported using several pot-type filtration devices. A currently used flow-type test apparatus is expected to simultaneously provide radionuclide elimination prior to ingestion and protection from internal exposure by accidental ingestion of radionuclides through the use of a micro-carbon carboxymethyl cartridge unit and an electrochemically reduced water production unit, respectively. However, the removability of radionuclides from contaminated tap water has not been tested to date. Thus, the current research was undertaken to assess the capability of the apparatus to remove radionuclides from artificially contaminated tap water. The results presented here demonstrate that the apparatus can reduce radioactivity levels to below the detection limit in applied tap water containing either 300 Bq/kg of ¹³⁷Cs or 150 Bq/kg of ¹²⁵I. The apparatus had a removal efficiency of over 90% for all concentration ranges of radio–cesium and –iodine tested. The results showing efficient radionuclide removability, together with previous studies on molecular hydrogen and platinum nanoparticles as reactive oxygen species scavengers, strongly suggest that the test apparatus has the potential to offer maximum safety against radionuclide-contaminated foodstuffs, including drinking water.     

Concentration of Radiocesium in the Wild Japanese Monkey (Macaca fuscata) over the First 15 Months after the Fukushima Daiichi Nuclear Disaster

Following the massive earthquake that struck eastern Japan on March 11, 2011, a nuclear reactor core meltdown occurred at the Fukushima Daiichi Nuclear Power Plant, operated by Tokyo Electric Power Company, and was followed by the release of large amounts of radioactive materials. The objective of this study was to measure the concentration of radiocesium ¹³⁴Cs and ¹³⁷Cs in the muscle of Japanese monkeys (Macaca fuscata) inhabiting the forest area of Fukushima City and to determine the change in concentration over time as well as the relationship with the level of soil contamination. Cesium concentrations in the muscle of monkeys captured at locations with 100,000–300,000 Bq/m² were 6,000–25,000 Bq/kg in April 2011 and decreased over 3 months to around 1,000 Bq/kg. However, the concentration increased again to 2,000–3,000 Bq/kg in some animals during and after December 2011 before returning to 1,000 Bq/kg in April 2012, after which it remained relatively constant. This pattern of change in muscle radiocesium concentration was similar to that of the change in radiocesium concentration in atmospheric fallout. Moreover, the monkeys feed on winter buds and the cambium layer of tree bark potentially containing higher concentrations of radiocesium than that in the diet during the rest of the year. The muscle radiocesium concentration in the monkeys related significantly with the level of soil contamination at the capture locations.     

DNA damage evaluated by the comet assay in lymphocytes of children with Cs internal contamination caused by the Chernobyl accident

The comet assay is one of the most versatile and popular tools for evaluating DNA damage. Its sensitivity to low dose radiation has been tested in vitro, but there are limited data showing its application and sensitivity in chronic exposure situations. The influence of the internal contamination caused by the Chernobyl accident on the level of DNA damage was evaluated by the comet assay on lymphocytes of 56 Ukrainian children. The study was performed during 2003 on children with demonstrable ¹³⁷Cs internal contamination caused by food consumption. The children were selected for the study immediately after a ¹³⁷Cs whole body counter measurement of internal contamination. The minimal detectable amount of ¹³⁷Cs was 75 Bq. The control group included 29 children without detectable internal contamination, while in the exposed group 27 children with measured activity between 80 and 4037 Bq and committed effective dose between 54 and 3155 μSv were included. Blood samples were taken by a finger prick. The alkaline version of the comet assay was used, in combination with silver stained comets and arbitrary units (AU), for comet measurement. Factors such as disease, medical treatment, surface contamination of children's living location, etc., were considered in the study. Non-significant differences (p > 0.05) in DNA damage in control (9.0 ± 5.7 AU) versus exposed (8.5 ± 4.8 AU) groups were found. These results suggest that low doses of ¹³⁷Cs internal contamination are not able to produce detectable DNA damage under the conditions used for the comet assay in this study. Further studies considering effects of high exposure should be performed on chronically exposed people using this assay.     

Assessment of the Annual Additional Effective Doses amongst Minamisoma Children during the Second Year after the Fukushima Daiichi Nuclear Power Plant Disaster

An assessment of the external and internal radiation exposure levels, which includes calculation of effective doses from chronic radiation exposure and assessment of long-term radiation-related health risks, has become mandatory for residents living near the nuclear power plant in Fukushima, Japan. Data for all primary and secondary children in Minamisoma who participated in both external and internal screening programs were employed to assess the annual additional effective dose acquired due to the Fukushima Daiichi nuclear power plant disaster. In total, 881 children took part in both internal and external radiation exposure screening programs between 1^st April 2012 to 31^st March 2013. The level of additional effective doses ranged from 0.025 to 3.49 mSv/year with the median of 0.70 mSv/year. While 99.7% of the children (n = 878) were not detected with internal contamination, 90.3% of the additional effective doses was the result of external radiation exposure. This finding is relatively consistent with the doses estimated by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The present study showed that the level of annual additional effective doses among children in Minamisoma has been low, even after the inter-individual differences were taken into account. The dose from internal radiation exposure was negligible presumably due to the success of contaminated food control.     

Trends of Increasing Medical Radiation Exposure in a Population Hospitalized for Cardiovascular Disease (1970–2009)

Background

High radiation doses employed in cardiac imaging may increase cancer frequency in exposed patients after decades. The aim of this study was to evaluate the relative trends in medical radiation exposure in a population hospitalized for cardiovascular disease.

Methods and Results

An observational single-center study was conducted to examine 16,431 consecutive patients with heart disease admitted to the Italian National Research Council Institute of Clinical Physiology between January 1970 and December 2009. In all patients, the cumulative estimated effective dose was obtained from data mining of electronic records of hospital admissions, adopting the effective dose typical values of the American Heart Association 2009 statement and Mettler’s 2008 catalog of doses. Cumulative estimated effective dose per patient in the last 5 years was 22 (12–42) mSv (median, 25^th–75^th percentiles), with higher values in ischemic heart disease (IHD), 37 (20–59) vs non-IHD, 13 (8–22) mSv, p<0.001. Trends in radiation exposure showed a steady increase in IHD and a flat trend in non-IHD patients, with variation from 1970–74 to 2005–2009 of +155% for IHD (p<0.001) and −1% in non-IHD (NS). The relative contribution of different imaging techniques was remodeled over time, with nuclear cardiology dominating in 1970s (23% of individual exposure) and invasive fluoroscopy in the last decade (90% of individual exposure).

Conclusion

A progressive increase in cumulative estimated effective dose is observed in hospitalized IHD patients. The growing medical radiation exposure may encourage a more careful justification policy regarding ionizing imaging in cardiology patients applying the two main principles of radiation protection: appropriate justification for ordering and performing each procedure, and careful optimization of the radiation dose used during each procedure.     

Assessment of Natural Radioactivity Levels and Potential Radiological Risks of Common Building Materials Used in Bangladeshi Dwellings

The concentrations of primordial radionuclides (²²⁶Ra, ²³²Th and ⁴⁰K) in commonly used building materials (brick, cement and sand), the raw materials of cement and the by-products of coal-fired power plants (fly ash) collected from various manufacturers and suppliers in Bangladesh were determined via gamma-ray spectrometry using an HPGe detector. The results showed that the mean concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in all studied samples slightly exceeded the typical world average values of 50 Bq kg⁻¹, 50 Bq kg⁻¹ and 500 Bq kg⁻¹, respectively. The activity concentrations (especially ²²⁶Ra) of fly-ash-containing cement in this study were found to be higher than those of fly-ash-free cement. To evaluate the potential radiological risk to individuals associated with these building materials, various radiological hazard indicators were calculated. The radium equivalent activity values for all samples were found to be lower than the recommended limit for building materials of 370 Bq kg^-1, with the exception of the fly ash. For most samples, the values of the alpha index and the radiological hazard (external and internal) indices were found to be within the safe limit of 1. The mean indoor absorbed dose rate was observed to be higher than the population-weighted world average of 84 nGy h^–1, and the corresponding annual effective dose for most samples fell below the recommended upper dose limit of 1 mSv y^–1. For all investigated materials, the values of the gamma index were found to be greater than 0.5 but less than 1, indicating that the gamma dose contribution from the studied building materials exceeds the exemption dose criterion of 0.3 mSv y^-1 but complies with the upper dose principle of 1 mSv y⁻¹.     

External and internal irradiation of a Rural Bryansk (Russia) population from 1990 to 2000, following high deposition of radioactive caesium from the chernobyl accident

In 1990, a joint Nordic-Russian project was initiated in order to make independent estimations of the effective dose to selected groups of inhabitants in a highly contaminated area around the city of Novozybkov in the western Bryansk region of Russia. The inhabitants were living in six villages with initial contamination levels of ¹³⁷Cs between 0.9 and 2.7 MBq m⁻². Some villages had been decontaminated, others not. Both school children and adults participated in the study. The external irradiation of 100–130 inhabitants was determined during 1 month in September-October each year from 1990 to 2000 (except 1999), using individual thermoluminescent dosemeters. The body burden of ^137,134Cs was determined by in vivo measurements in about 500 inhabitants annually from 1991 to 2000, and for a subgroup also with analysis of the ¹³⁷Cs concentration in urine. The mean effective dose (E) from external and internal irradiation due to ^137,134Cs deposition varied between 2.5 and 1.2 mSv per year between 1990 and 2000. The total mean E decreased, on average, by 9% per year, while the mean external dose decreased by 16% per year. The dose rate from internal radiation decreased more slowly than the dose rate from external radiation, and also showed an irregular time variation. The contribution from the internal dose to the total E was 30–50%, depending on the village. Predictions for the long-term changes in the effective dose to people living in the areas are presented. The cumulated E for the 70 years following the accident was estimated to be about 90 mSv with the assumption that both internal and external dose decrease by 2% per year after year 2000. The highest E during a life-time received by single individuals living in the area may amount to around 500 mSv considering the individual variations in E.     

Measurement of <Superscript>131</Superscript>I activity in thyroid of nuclear medical staff and internal dose assessment in a Polish nuclear medical hospital

This paper presents results of ¹³¹I thyroid activity measurements in 30 members of the nuclear medicine personnel of the Department of Endocrinology and Nuclear Medicine Holy Cross Cancer Centre in Kielce, Poland. A whole-body spectrometer equipped with two semiconductor gamma radiation detectors served as the basic research instrument. In ten out of 30 examined staff members, the determined ¹³¹I activity was found to be above the detection limit (DL = 5 Bq of ¹³¹I in the thyroid). The measured activities ranged from (5 ± 2) Bq to (217 ± 56) Bq. The highest activities in thyroids were detected for technical and cleaning personnel, whereas the lowest values were recorded for medical doctors. Having measured the activities, an attempt has been made to estimate the corresponding annual effective doses, which were found to range from 0.02 to 0.8 mSv. The highest annual equivalent doses have been found for thyroid, ranging from 0.4 to 15.4 mSv, detected for a cleaner and a technician, respectively. The maximum estimated effective dose corresponds to 32% of the annual background dose in Poland, and to circa 4% of the annual limit for the effective dose due to occupational exposure of 20 mSv per year, which is in compliance with the value recommended by the International Commission on Radiological Protection.     

Procédures de ventilation pulmonaire par aérosol Tc-DTPA : contamination aérienne, contaminations interne et cutanée externe des manipulateurs

Efficiency of an optimization procedure of radiation protection measures with lung ventilation by ^99mTc-DTPA aerosol was evaluated by measuring airborne radioactivity and by looking for external and internal contaminations of technologists. Despite numerous precautions, small amounts of radioactivity were airborne in 71.4% of procedures and a small internal contamination of technologists (1.6–881 Bq; median: 36.3 Bq) was found. The latter was highest in case of deficient patient collaboration and with technical incidents. A very low external contamination (0.1-29.1 Bq; median: 0.1 Bq) was demonstrated with 82% of procedures. Estimated effective doses by internal contamination (0.01-6.2 nSv; median 0.3 nSv) was minimal compared with the maximal legally admissible doses for professionally exposed workers (10 mSv/year); it does not represent an excessive irradiation risk.     

Estimation of dose rate for indoor radon from building materials

The internal dose rate due to indoor radon (Rn) emissions from building materials is estimated. It is observed that the contribution from building materials to the dose rate is very small. The average indoor radon concentration in 75 different rooms is found to be 55 ± 12 Bq. m^–3. Assuming an occupancy factor of 0.8, the annual average effective dose equivalent is 1.7 mSv. It seems that soil gas is mainly responsible for the internal exposure from indoor Rn.     

Long-term external radiation exposure of inhabitants in the western Bryansk region of Russia as a consequence of the Chernobyl accident

The western Bryansk region in south-western Russia was highly contaminated with ¹³⁷Cs and ¹³⁴Cs due to the Chernobyl accident in 1986. In 1990, a joint Nordic-Russian project was initiated in order to make measurements and estimates of the absorbed doses to selected groups of inhabitants in this area. The participating individuals were living in small villages with contamination levels between 0.9 and 2.7 MBq m^–2. Only some villages had been decontaminated. Both schoolchildren and adults participated in the study and the number of persons was between 100 and 130 each year, residing in 5 villages. Every year in September–October, from 1990 to 1998, we performed individual measurements of external absorbed doses, assessed with thermoluminescent (TL) dosemeters (LiF). The mean effective dose per year from external irradiation due to the Chernobyl accident of the inhabitants in the villages ranged between 0.8 and 2.9 mSv during the study period and decreased with an apparent half-time of 3.7–8.2 years, depending on village and group. The highest individual doses within one village were, on average higher by a factor of 3 than the mean value for that village. Under the conservative assumption of a decrease rate in the external effective dose of 2% per year after 1998, individuals in the most highly exposed village are assumed to receive a life-time effective dose of about 75 mSv (between 1986 and 2056) from external exposure to caesium radionuclides. The mean value for the villages under study was estimated to be around 65 mSv using the assumed rate of decrease. Received: 20 December 2000 / Accepted: 1 October 2001     

Chronic Internal Exposure to Low Dose 137Cs Induces Positive Impact on the Stability of Atherosclerotic Plaques by Reducing Inflammation in ApoE-/- Mice

After Chernobyl and Fukushima Daï Chi, two major nuclear accidents, large amounts of radionuclides were released in the environment, mostly caesium 137 (¹³⁷Cs). Populations living in contaminated territories are chronically exposed to radionuclides by ingestion of contaminated food. However, questions still remain regarding the effects of low dose ionizing radiation exposure on the development and progression of cardiovascular diseases. We therefore investigated the effects of a chronic internal exposure to ¹³⁷Cs on atherosclerosis in predisposed ApoE^-/- mice. Mice were exposed daily to 0, 4, 20 or 100 kBq/l ¹³⁷Cs in drinking water, corresponding to range of concentrations found in contaminated territories, for 6 or 9 months. We evaluated plaque size and phenotype, inflammatory profile, and oxidative stress status in different experimental groups. Results did not show any differences in atherosclerosis progression between mice exposed to ¹³⁷Cs and unexposed controls. However, ¹³⁷Cs exposed mice developed more stable plaques with decreased macrophage content, associated with reduced aortic expression of pro-inflammatory factors (CRP, TNFα, MCP-1, IFNγ) and adhesion molecules (ICAM-1, VCAM-1 and E-selectin). Lesions of mice exposed to ¹³⁷Cs were also characterized by enhanced collagen and smooth muscle cell content, concurrent with reduced matrix metalloproteinase MMP8 and MMP13 expression. These results suggest that low dose chronic exposure of ¹³⁷Cs in ApoE^-/- mice enhances atherosclerotic lesion stability by inhibiting pro-inflammatory cytokine and MMP production, resulting in collagen-rich plaques with greater smooth muscle cell and less macrophage content.     

Analysis of Plasma Protein Concentrations and Enzyme Activities in Cattle within the Ex-Evacuation Zone of the Fukushima Daiichi Nuclear Plant Accident

The effect of the Fukushima Daiichi Nuclear Power Plant (FNPP) accident on humans and the environment is a global concern. We performed biochemical analyses of plasma from 49 Japanese Black cattle that were euthanized in the ex-evacuation zone set within a 20-km radius of FNPP. Among radionuclides attributable to the FNPP accident, germanium gamma-ray spectrometry detected photopeaks only from ¹³⁴Cs and ¹³⁷Cs (radiocesium) commonly in the organs and in soil examined. Radioactivity concentration of radiocesium was the highest in skeletal muscles. Assuming that the animal body was composed of only skeletal muscles, the median of internal dose rate from radiocesium was 12.5 μGy/day (ranging from 1.6 to 33.9 μGy/day). The median of external dose rate calculating from the place the cattle were caught was 18.8 μGy/day (6.0–133.4 μGy/day). The median of internal and external (total) dose rate of the individual cattle was 26.9 μGy/day (9.1–155.1 μGy/day). Plasma levels of malondialdehyde and superoxide dismutase activity were positively and glutathione peroxidase activity was negatively correlated with internal dose rate. Plasma alanine transaminase activity and percent activity of lactate dehydrogenase (LDH)-2, LDH-3 and LDH-4 were positively and LDH-1 was negatively correlated with both internal and total dose rate. These suggest that chronic exposure to low-dose rate of ionizing radiation induces slight stress resulting in modified plasma protein and enzyme levels.     

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.     

Estimated Dietary Intake of Radionuclides and Health Risks for the Citizens of Fukushima City,Tokyo, and Osaka after the 2011 Nuclear Accident

The radionuclides released from the Fukushima Daiichi nuclear power plant in 2011 pose a health risk. In this study, we estimated the 1st-year average doses resulting from the intake of iodine 131 (¹³¹I) and cesium 134 and 137 (¹³⁴Cs and ¹³⁷Cs) in drinking water and food ingested by citizens of Fukushima City (∼50 km from the nuclear power plant; outside the evacuation zone), Tokyo (∼230 km), and Osaka (∼580 km) after the accident. For citizens in Fukushima City, we considered two scenarios: Case 1, citizens consumed vegetables bought from markets; Case 2, citizens consumed vegetables grown locally (conservative scenario). The estimated effective doses of ¹³⁴Cs and ¹³⁷Cs agreed well with those estimated through market basket and food-duplicate surveys. The average thyroid equivalent doses due to ingestion of ¹³¹I for adults were 840 µSv (Case 1) and 2700 µSv (Case 2) in Fukushima City, 370 µSv in Tokyo, and 16 µSv in Osaka. The average effective doses due to ¹³⁴Cs and ¹³⁷Cs were 19, 120, 6.1, and 1.9 µSv, respectively. The doses estimated in this study were much lower than values reported by the World Health Organization and the United Nations Scientific Committee on the Effects of Atomic Radiation, whose assessments lacked validation and full consideration of regional trade in foods, highlighting the importance of including regional trade. The 95th percentile effective doses were 2–3 times the average values. Lifetime attributable risks (LARs) of thyroid cancers due to ingestion were 2.3–39×10⁻⁶ (Case 1) and 10–98×10⁻⁶ (Case 2) in Fukushima City, 0.95–14×10⁻⁶ in Tokyo, and 0.11–1.3×10⁻⁶ in Osaka. The contributions of LARs of thyroid cancers due to ingestion were 7.5%–12% of all exposure (Case 1) and 12%–30% (Case 2) in Fukushima City.     

Frequency of dominant lethal mutations induced by combined exposure to incorporated 137Cs and external gamma-irradiation in mice

The genetic effect of combined exposure to incorporated 137Cs and external gamma-irradiation was studied in germ cells of male mice. The activity of incorporated 137Cs was 3.7 x 10(4) Bq/g. The dose of external gamma-irradiation was 1.5 Gy. In the case of combined exposure, mice were treated with a cesium solution immediately after irradiation. The genetic effect was estimated by the frequency of dominant lethal mutations (DLM) induced at different stages of spermatogenesis. Upon combined exposure to external and internal irradiation, the frequency of DLM in premeiotic cells significantly exceeded the total frequency of DLM induced by separate exposure to external and internal irradiation; i.e., a marked synergistic interaction of external and internal irradiation was observed.