Depertment of Radiation Science, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan; Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan.
Depertment of Radiation Science, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan; Center for Technology of Radiation Safety and Metrology, National Nuclear Energy Agency, JI. Lebak Bulus Raya No. 49, Jakarta 12440, Indonesia.
Sci Total Environ. 2021 Jan 1;750:142346. doi: 10.1016/j.scitotenv.2020.142346. Epub 2020 Sep 15.
The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h and 1109 nGy h. Indoor radon concentrations ranged from 124 Bq m to 1015 Bq m. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.
低剂量率辐射对人类的生物学效应尚不清楚。事实上，福岛第一核电站事故后，日本仍在努力应对这一问题。最近，我们在印度尼西亚发现了一个独特的地区，那里自然存在高辐射水平，导致慢性低剂量率辐射暴露。我们旨在估算该特别高天然辐射区的内外照射综合剂量，并讨论氡的增强机制。我们进行了车载调查，以估算陆地辐射的外照射剂量。在三个至五个月的时间里，在 47 个住宅中进行了室内氡测量，以估算内照射剂量，涵盖了两个典型的季节。同时在几个高度收集大气氡气，以评估垂直分布。研究区域的空气吸收剂量率在 50 nGy h 至 1109 nGy h 之间变化很大。室内氡浓度范围从 124 Bq m 至 1015 Bq m。也就是说，所测量的室内氡浓度超过了世界卫生组织建议的 100 Bq m 的参考水平。此外，所测量的室外氡浓度与高室内氡浓度相当。使用中值估计研究区域内外照射的年有效剂量为 27 mSv。结果发现，许多居民受到天然放射性核素的辐射照射，超过了职业辐射工作人员的剂量限值。这种增强的室外氡浓度可能是由于异常低海拔产生的稳定大气条件所致。我们的研究结果表明，该地区为开展与慢性低剂量率辐射暴露相关的健康影响的流行病学研究提供了独特的机会。
