Outdoor decontamination efforts have been ongoing since the Fukushima Daiichi nuclear power plant (FDNPP) accident; however, little is known about indoor contamination. Therefore, house dust was sampled based on particle size in 21 wooden buildings (19 residential houses and 2 community centers) within the evacuation area close to the FDNPP, Fukushima Prefecture, Japan. Activities of radiocesium (¹³⁷Cs) per gram of house dust increased with decreasing particle size (mean: 6.1 × 10³, 2.6 × 10³, 1.6 × 10³, 7.5 × 10², 5.0 × 10², and 4.6 × 10² Bq/g for <4–20, 20–63, 63–180, 180–500, 500–1000, and 1000–2000 μm, respectively). The ¹³⁷Cs concentrations in house dust were inversely related to the square of distance from the FDNPP for <4–1000 μm particles. From the results of the multiple linear regression analysis, distance from the FDNPP and direction from the FDNPP (northwest) were significantly related to the radioactivity of house dust. It was found that 19%, 33%, and 48% of ¹³⁷Cs in house dust were extracted in water, 1 M HCl, and not extracted, respectively. Considering the bioaccessibility and assuming a 20 mg/day daily intake of house dust, the daily doses would be 7.2 Bq/day (mean) and 18 Bq/day (95th percent quantile). These results provide valuable insight into indoor radioactive Cs contamination in the area around the FDNPP and possible oral exposure to indoor radioactive Cs after returning home.

自福岛第一核电站事故发生以来，室外除污工作一直在进行。但是，对室内污染知之甚少。因此，根据日本福岛县FDNPP附近疏散区域内21座木制建筑物（19座民居和2个社区中心）中的灰尘，对房屋灰尘进行了采样。放射性铯（活动¹³⁷每克的屋尘Cs）的随粒径（平均增加：6.1×10 ³，2.6×10 ³，1.6×10 ³，7.5×10 ²，5.0×10 ²，和4.6×10 ²  Bq / g分别小于4-20、20-63、63-180、180-500、500-1000和1000-2000μm）。在¹³⁷对于<4–1000μm的颗粒，室内灰尘中的Cs浓度与距FDNPP的距离的平方成反比。从多元线性回归分析的结果来看，离FDNPP的距离和距FDNPP的方向（西北）与房屋扬尘的放射性显着相关。发现在室内灰尘中¹³⁷ Cs的19％，33％和48％分别在水中，1 M HCl中提取和未提取。考虑到生物可及性，并假设每天摄入20毫克/天的室内灰尘，则每日剂量应为7.2 Bq /天（平均）和18 Bq /天（95％的分位数）。这些结果为FDNPP周围区域的室内放射性Cs污染以及回家后可能的口腔内放射性Cs暴露提供了有价值的见解。