Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki University, 1-12-4 Sakamoto, Nagasaki City, Nagasaki, 852-8523, Japan.
Sci Rep. 2020 Nov 5;10(1):19215. doi: 10.1038/s41598-020-75857-1.
In recent years, Japan has suffered serious damage due to natural disasters such as earthquakes, heavy rains due to tropical storms (typhoons) and localized downpours. To assess the chronological changes in the attenuation of external exposure doses and environmental radiation contamination due to the rainfall associated with typhoons and heavy rains during October to December 2019 in Fukushima, we measured environmental radiation levels in forest areas along the Mt Okura hiking trail in Tomioka Town, Fukushima Prefecture, near the Fukushima Daiichi Nuclear Power Station. We confirmed that (1) current ambient dose rates of 0.38-0.95 μSv/h in most forest areas were 79.9-84.7% higher than in residential areas; (2) the number of sites along the hiking trail where Cs was detected was limited (1.1-4.7%); and (3) individual dose rates of 0.21-0.34 μSv/h were lower than ambient dose rates. These findings suggest that radiocesium has remained stable in natural forests that have not been decontaminated even though current levels are low, despite the occurrence of heavy rainfall associated with Super Typhoon Hagibis in 2019 and localized downpours. Hiking while managing exposure to environmental contamination using a personal dosimeter may be the safest model for spending time of leisure activities.
近年来，日本因地震、热带风暴（台风）引发的暴雨和局部强降雨等自然灾害遭受了严重破坏。为评估 2019 年 10 月至 12 月福岛县富冈市 Mt Okura 徒步旅行径沿线森林地区因台风和暴雨导致的外照射剂量和环境辐射污染衰减的时间变化，我们测量了福岛第一核电站附近的环境辐射水平。我们确认：（1）大多数森林地区的当前环境剂量率为 0.38-0.95μSv/h，比住宅区高 79.9-84.7%；（2）徒步旅行径沿线检测到 Cs 的地点数量有限（1.1-4.7%）；（3）0.21-0.34μSv/h 的个体剂量率低于环境剂量率。这些发现表明，尽管当前水平较低，但在 2019 年超级台风“海贝思”引发的暴雨和局部强降雨之后，即使未进行去污，天然森林中的放射性铯仍保持稳定。使用个人剂量计管理对环境污染的照射，进行徒步旅行可能是休闲活动的最安全模式。
