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Concept: Cabinet of Japan


The Fukushima nuclear accident released radioactive materials into the environment over the entire Northern Hemisphere in March 2011, and the Japanese government is spending large amounts of money to clean up the contaminated residential areas and agricultural fields. However, we still do not know the exact physical and chemical properties of the radioactive materials. This study directly observed spherical Cs-bearing particles emitted during a relatively early stage (March 14-15) of the accident. In contrast to the Cs-bearing radioactive materials that are currently assumed, these particles are larger, contain Fe, Zn, and Cs, and are water insoluble. Our simulation indicates that the spherical Cs-bearing particles mainly fell onto the ground by dry deposition. The finding of the spherical Cs particles will be a key to understand the processes of the accident and to accurately evaluate the health impacts and the residence time in the environment.

Concepts: Solubility, Chemical substance, Chemical element, Uranium, Radioactive contamination, Lists of nuclear disasters and radioactive incidents, Government of Japan, Cabinet of Japan


Since the Cabinet’s decision concerning the Basic Policies 2005, the Japanese government has implemented specific measures to suppress increases in national medical care expenditure. However, we believe that the economic significance of medical care should be quantified in terms of its economic impact on national medical care expenditure. No one has examined the economic impact of all medical institutions in Japan using data from a statement of profits and losses. We used an input-output analysis to quantitatively estimate economic impact of medical care and examined its estimation range with a probabilistic sensitivity analysis.

Concepts: Health care, Statistics, Economics, Government of Japan, Info-gap decision theory, Cabinet of Japan, Constitution of Japan, House of Representatives of Japan


In an unprecedented food monitoring campaign for radionuclides, the Japanese government took action to secure food safety after the Fukushima nuclear accident (11 March 2011). In this paper we analyze a part of the immense data set, in particular radiocesium contaminations in food from the first year after the accident. Activity concentrations in vegetables peaked immediately after the campaign had commenced, but they decreased quickly, so that by early summer 2011 only few samples exceeded the regulatory limits. Later, accumulating mushrooms and dried produce led to several exceedances of the limits again. Monitoring of meat started with significant delay, especially outside Fukushima prefecture. After a buildup period, contamination levels of meat peaked by July 2011 (beef). Levels then decreased quickly, but peaked again in September 2011, which was primarily due to boar meat (a known accumulator of radiocesium). Pre-Fukushima 137Cs and 90Sr levels (resulting from atmospheric nuclear explosions) in food were typically lower than 0.5 Bq/kg, whereby meat was typically higher in 137Cs, and vegetarian produce was usually higher in 90Sr. The correlation of background radiostrontium and radiocesium indicated that the regulatory assumption after the Fukushima accident of a maximum activity of 90Sr being 10% of the respective 137Cs concentrations may soon be at risk, as the 90Sr/137Cs ratio increases with time. This should be taken into account for the current Japanese food policy as the current regulation will soon underestimate the 90Sr content of Japanese foods.

Concepts: Nuclear medicine, Food, Japan, Radioactive contamination, Prefectures of Japan, Government of Japan, Honshū, Cabinet of Japan


The Japanese government ordered the analysis of thousands of foods after the Fukushima nuclear accident to ascertain compliance with regulatory limits for anthropogenic radionuclides in food. Four hundred and fourty five samples from 11 prefectures exceeded the regulatory limits that were in force until 31 March 2011. The possibility of these 445 samples representing localized areas of high radiocesium concentration was investigated. The objective of this study was to determine the radiocesium activity ratio (134Cs/137Cs) in foods from each geographic area to possibly identify the radioactive signature of the four different reactors (i.e. four independent sources) in the distinct regions. The average 134Cs/137Cs activity ratio was 0.98+/-0.01 for all samples. However, no clear deviations from this value could be confirmed in the various regions. Since there was no statistically significant deviation in the radiocesium activity ratio, the releases from reactor No. 4 (carrying a significantly smaller activity ratio) are assumed to be small when compared with the other three reactor release. The individual radioisotopic signatures of reactors No. 1, 2, and 3 could not be identified in various Japanese regions using the food samples, indicating integral radiocesium contamination from these sources. Subsequent releases of fission products from the reactors (e.g. after possible criticalities reported in October 2011) proved to have no impact on the radiocesium activity ratio. A discussion of the development of the regulatory limits in Japan and Europe with regard to the current limits and radiological food safety are also included.

Concepts: Food, Radioactive decay, Japan, Standard deviation, Radioactive contamination, Prefectures of Japan, Government of Japan, Cabinet of Japan


After the nuclear disaster in Fukushima on 11 March 2011, some businesses were permitted to continue operating even though they were located in the evacuation area designated by the Japanese government. The aim of this study was to examine differences in the mental health status, workplace, living environment, and lifestyle of employees in the evacuation and non-evacuation areas. We also investigated factors related to their mental health status. Data for this cross-sectional study were collected from the questionnaire responses of 647 employees at three medium-sized manufacturing companies in the evacuation and non-evacuation areas. Through a cross-tabulation analysis, employees who worked at companies in the evacuation areas showed an increase in the duration of overtime work, work burden, and commute time, and had experienced separation from family members due to the radiation disaster and perceived radiation risks. The results of a multivariate logistic regression analysis showed that, even in a harsh workplace and living environment, being younger, participating regularly in physical activity, having a social network (Lubben Social Network Scale-6 ≤ 12), laughing frequently, and feeling satisfied with one’s workplace and domestic life were significantly associated with maintaining a healthy mental health status after the disaster. These findings are applicable for workers' health management measures after disasters.

Concepts: Regression analysis, Logistic regression, Epidemiology, Econometrics, Sociology, Hazard, Government of Japan, Cabinet of Japan


Instead of conventional Ge semiconductor detectors and NaI(Tl) scintillation spectrometers, an application of a CdZnTe semiconductor (CZT) whose crystal has the dimension of 1 cm cubic to the in situ environmental radioactivity measurement was attempted in deeply affected areas in Fukushima region. Results of deposition density on soil for (134)Cs/(137)Cs obtained seemed consistent, comparing obtained results with those measured by the Japanese government.

Concepts: Measurement, Signal processing, Silicon, Units of measurement, Diode, Prefectures of Japan, Government of Japan, Cabinet of Japan


Amid continuing social unrest from the Great East Japan Earthquake and subsequent Fukushima nuclear accident of 2011, the Japanese government announced plans for a major biobanking project in the disaster-stricken areas, to be administered by the ‘Tohoku Medical Megabank Organization’ (ToMMo). This project differs from previous biobanking projects in that it 1) was initiated mainly to boost post-disaster recovery and reconstruction; and 2) targets the area’s survivors as its primary subjects. Here, we review the ethics of the ToMMo biobanking project within the wider context of disaster remediation.

Concepts: Japan, Prefectures of Japan, Government of Japan, Fukushima Prefecture, Tōhoku region, Cabinet of Japan, Constitution of Japan, House of Representatives of Japan


The Fukushima Daiichi accident released huge amounts of radioactive material over a wide area. We can appreciate the geographical extent of radioactive contamination from the information published online by the Japanese government. Historically, this is an unprecedented situation, which allows “natural experimentation” to estimate the causal effects of radioactive contamination on our society. This study focused on property value losses caused by the accident and analyzed changes in land appraisals around the Fukushima Daiichi plant from July 2010 to July 2011 within the framework of hedonic approach. Thus, we estimated the short-run impact of the contamination or the change in marginal value of proximity to the plant. The results suggest that the appraisals significantly and monotonically depreciated with increasing contamination levels. However, there was no evidence to suggest changes in the marginal value of proximity to the plant. A comparison between the appraisals and transaction prices indicates that this result could be interpreted as an underestimate of actual property value losses.

Concepts: Causality, Economics, Radioactive decay, Radioactive contamination, Radionuclide, Radioactive waste, Government of Japan, Cabinet of Japan