Temporal variations in ambient dose rates in a restricted area designated as "difficult-to-return" for residents of Tomioka Town, Fukushima Prefecture were evaluated in a car-borne survey during 2018-2019. The median dose rates in the "Decontaminated area" in the difficult-to-return zone decreased rapidly from 1.0 μSv/h to 0.32 μSv/h; however, the median dose rates in the "Non-decontaminated area" and "Radioactive waste storage area" fluctuated between 1.1-1.4 μSv/h and 0.46-0.61 μSv/h, respectively. The detected rate of the cesium-137 (137 Cs) (137 Cs-detected points per all measuring points) in the "Decontaminated area" also decreased rapidly from 64% to 6.7%, accompany with decreasing in ambient dose rates. On the other hand, the detection of 137 Cs in the "Radioactive waste storage area" and "Non-decontaminated area" decreased from 53% to 17% and 93% to 88%, respectively. We confirmed that the dose rates in the Decontaminated area dramatically decreased due to decontamination work aiming to help residents return home. Moreover, the estimated external exposure dose of workers during the present survey was 0.66 mSv/y in the Decontaminated area and 0.55 mSv/y in the Radioactive waste storage area, respectively. This case of Tomioka Town within the "difficult-to-return zone" may be the first reconstruction model for evaluating environmental contamination and radiation exposure dose rates due to artificial radionuclides derived from the nuclear disaster. The Great East Japan Earthquake (magnitude 9.0) and subsequent tsunami on March 11, 2011 caused an accident at the Fukushima Daiichi Nuclear Power Station (FDNPS) that resulted in various radionuclides including cesium-134 (134 Cs), cesium-137 (137 Cs) and iodine-131(131 I) being released into the atmosphere and eventually depositing on land and at sea in the surrounding areas 1. The United Nations Scientific Committee on the Effects of Atomic Radiation estimated the total release of 134 Cs (half-life: 2.1 y), 137 Cs (half-life: 30 y) and 131 I (half-life: 8 d) to be 9.0, 8.8 and 120.0 petabecquerels (PBq), respectively 1. The Japanese government, municipalities and private companies have carried out environmental and individual radiation monitoring programs to confirm the radiation levels in the affected areas 2,3. More than 8 years have passed since the accident and it has been confirmed that artificial radionuclides with a relatively long half-life such as 134 Cs and 137 Cs still exist in soil and plant samples collected around the FDNPS 1-3. Environmental monitoring in Fukushima Prefecture have been carried out by many methods (the airborne survey by monitor stations and personnel, vehicle-borne survey, aerial-vehicle survey and radionuclide analysis of the environmental samples such as soils, sediments and foodstuffs) 3-9. These surveys and the collected data are extremely important to precise evaluation of environmental remediation in the affected areas. Following the FDNPS accident, residential areas, farmlands, forests close to residential areas, and roads...

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 released large amounts of artificial radioactive substances into the environment. In this study, we measured the concentration of radiocesium (134 cs + 137 Cs) in 213 muscle samples from wild boars (Sus scrofa) captured in Tomioka town, which is located within 20 km of the FDNPP. The results showed that 210 (98.6%) muscle samples still exceeded the regulatory radiocesium limit (100 Bq/kg) for general foods. Radiocesium (134 cs + 137 Cs) levels ranged from 87.1-8,120 Bq/kg fresh mass (FM), with a median concentration of 450 Bq/kg FM. The median committed effective dose was estimated to be 0.070-0.26 μSv/day for females and 0.062-0.30 μSv/day for males. The committed effective dose for one-time ingestion of wild boar meat could be considered extremely low for residents in Tomioka. The relatively high levels of radioactivity found in this study suggest that the high variability of food sources may have led to the large accumulation of radioactive substances. These results suggest that comprehensive long-term monitoring is needed to identify risk factors affecting recovery from a nuclear disaster.

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Following the Fukushima Daiichi Nuclear Power Plant accident in March 2011, radionuclides such as iodine-131, cesium-134 and cesium-137 were released into environment. In this study, we collected wild mushrooms from the Kawauchi Village of Fukushima Prefecture, located less than 30 km southwest of the Fukushima nuclear power plant, to evaluate their radiocesium (134 Cs+ 137 Cs) concentrations and the risk of internal radiation exposure in local residents. 342 mushroom samples were collected from 2016 to 2019. All samples were analysed for radiocesium content by a high-purity germanium detector. Among 342 mushroom samples, 260 mushroom samples (76%) were detected the radiocesium exceeding the regulatory limit of radiocesium (100 Bq/kg for general foods in Japan). The median of committed effective dose from ingestion of wild mushrooms was in the range of 0.015-0.053 mSv in 2016, 0.0025-0.0087 mSv in 2017, 0.029-0.110 mSv in 2018 and 0.011-0.036 mSv in 2019 based on the assumption that Japanese citizens consumed wild mushrooms for 1 year. Thus, our study showed that although radiocesium is still detected in mushrooms collected in Kawauchi village even after 5 to 9 years later, the committed effective dose due to consuming mushrooms was lower than 1 mSv per year. Long-term comprehensive follow-up should monitor radiocesium concentrations in wild mushrooms to support the recovery of the community after the nuclear disaster.

Background YouTube (Alphabet Incorporated) has become the most popular video-sharing platform in the world. The Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster resulted in public anxiety toward nuclear power and radiation worldwide. YouTube is an important source of information about the FDNPP disaster for the world. Objective This study's objectives were to examine the characteristics of YouTube videos related to the FDNPP disaster, analyze the content and comments of videos with a quantitative method, and determine which features contribute to making a video popular with audiences. This study is the first to examine FDNPP disaster–related videos on YouTube. Methods We searched for the term “Fukushima nuclear disaster” on YouTube on November 2, 2019. The first 60 eligible videos in the relevance, upload date, view count, and rating categories were recorded. Videos that were irrelevant, were non-English, had inappropriate words, were machine synthesized, and were <3 minutes long were excluded. In total, 111 videos met the inclusion criteria. Parameters of the videos, including the number of subscribers, length, the number of days since the video was uploaded, region, video popularity (views, views/day, likes, likes/day, dislikes, dislikes/day, comments, comments/day), the tone of the videos, the top ten comments, affiliation, whether Japanese people participated in the video, whether the video recorder visited Fukushima, whether the video contained theoretical knowledge, and whether the video contained information about the recent situation in Fukushima, were recorded. By using criteria for content and technical design, two evaluators scored videos and grouped them into the useful (score: 11-14), slightly useful (score: 6-10), and useless (score: 0-5) video categories. Results Of the 111 videos, 43 (38.7%) videos were useful, 43 (38.7%) were slightly useful, and 25 (22.5%) were useless. Useful videos had good visual and aural effects, provided vivid information on the Fukushima disaster, and had a mean score of 12 (SD 0.9). Useful videos had more views per day (P<.001), likes per day (P<.001), and comments per day (P=.02) than useless and slightly useful videos. The popularity of videos had a significant correlation with clear sounds (likes/day: P=.001; comments/day: P=.02), vivid information (likes/day: P<.001; comments/day: P=.007), understanding content (likes/day: P=.001; comments/day: P=.04). There was no significant difference in likes per day (P=.72) and comments per day (P=.11) between negative and neutral- and mixed-tone videos. Videos about the recent situation in Fukushima had more likes and comments per day. Video recorders who personally visited Fukushima Prefecture had more subscribers and received more views and likes. Conclusions The possible features that made videos popular to the public included video quality, videos made in Fukushima, and information on the recent situation in Fukushima. During risk communication on new forms of media, health institutes should increase publicity and be more approachable to resonate with international audiences.

The radioactive contamination in Beijing caused by the Japanese Fukushima nuclear accident was monitored. In this research, samples of air, rainwater, surface water and vegetables in Beijing were collected and measured to estimate the radioactive contamination levels in Beijing. During the period from the 15th to the 41st day after the first emission of radioactive material (first emission) from the Japanese Fukushima nuclear power station (NPS) on 12 March 2011, obvious radioactive contamination was found in the Beijing air samples. The maximum concentration of I-131 was 5.89 mBq m(-3) in the air samples detected on the 22nd day after the first emission, and the maximum concentration of Cs-137 and Cs-134 was found on the 20th day after the first emission. Except for one sample of rainwater, no artificial radionuclides associated with Fukushima were found in surface water. The measurement results showed that there was no harm to the health of local Beijing residents.

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The wearing method of personal dosemeters for medical staff changed from under to outside the operator’s protective apron in April 2020. We measured the radiation dose Hp(10) for medical staff in Beijing from September 2020 to October 2021. The study population consisted of 3291 medical staff. All participants were divided into three groups. After excluding unusually low doses, the collected data higher than the detection limit involved 811 (7.8%) of 10 395 readings from 479 (14.6%) of 3291 staff. The mean equivalent dose was 1.4 mSv/3 months, with an SD of 2.3 mSv. The calculated average annual effective doses of radiation workers in the three groups after the interventional procedures from September 2020 to October 2021 ranged from 0.47 to 0.63 mSv/year, with median values of 0.32, 0.23 and 0.26 mSv/year, respectively.