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⁻¹ and 1109 nGy h⁻¹. Indoor radon concentrations ranged from 124 Bq m⁻³ to 1015 Bq m⁻³. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m⁻³ 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.

低剂量率辐射对人体的生物学影响仍然未知。实际上，在福岛第一核电站事故发生后，日本民族仍在为这个问题而苦苦挣扎。最近，我们在印度尼西亚发现了一个自然存在高辐射水平的独特地区，导致长期低剂量率辐射暴露。我们的目的是估计在特别高的自然辐射区由于内部和外部暴露而引起的综合剂量，并讨论ra的增强机理。进行了一次车载调查，以估计地面辐射的外部剂量。在三个至五个月的时间内（覆盖两个典型季节）在47处住宅中进行室内ra测量，以估算内部剂量。同时在几个高度收集大气ra气以评估垂直分布。研究区域空气中的吸收剂量率在50 nGy h之间变化很大^-1和1109 nGy h ^-1。室内ra浓度范围为124 Bq m ^-3至1015 Bq m ^-3。也就是说，室内测得的ra浓度超过参考水平100 Bq m ^-3由世界卫生组织推荐。此外，所测得的室外ra浓度与室内高high浓度相当。使用中值，研究区域内外部和内部接触引起的年度有效剂量估计为27 mSv。已经发现，许多居民正在接受天然放射性核素的辐射暴露，其辐射剂量超过了对辐射工作人员的职业暴露的剂量限值。室外ra浓度的提高可能是由于在异常低空产生的稳定大气条件的结果。我们的研究结果表明，由于长期低剂量率辐射暴露，该领域为开展与健康影响相关的流行病学研究提供了独特的机会。