To support estimations of early individual internal doses to residents who suffered from the 2011 accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP), we have sought to use whole-body counter (WBC) measurement results of subjects who lived in municipalities neighboring the FDNPP at the time of the accident. These WBC measurements started several months after the accident; the targeted radionuclides were 134Cs and 137Cs. Our previous study had analyzed the relationship between the residual Cs contents of individuals and evacuation behaviors in the period immediately after the accident for residents of Namie-town, one of the most radiologically affected municipalities. Those results suggested that the first major release event at the FDNPP on 12 March 2011 caused significant exposure, particularly to those who delayed evacuation on that day. The present study expanded its scope to include subjects from four towns neighboring the FDNPP (Namie, Futaba, Okuma, and Tomioka) to gather additional evidence of the exposure that took place on 12 March 2011. Additionally, we investigated the relationship between individual cesium doses and subjects' destinations following the largest release event on 15 March 2011. The study population was 1,145 adults. We first divided the subjects into two evacuation groups depending on the distance from the FDNPP and their evacuation whereabouts (25-km boundary) as of 15:00 on 12 March 2011: the G1 group (≥25 km) and the G2 group (<25 km). We further divided these two subject groups into seven subgroups based on the subjects' destinations as of 0:00 on 16 March 2011. Our four main findings are as follows. (1) The 137Cs detection rate was significantly different between the G1 and G2 groups of Namie-town and Futaba-town but not for those of Okuma-town and Tomioka-town. This result corresponds to the plume passage (flowing toward the northwest to the north) in the afternoon of 12 March 2011 and supports our previous study. (2) The upper-percentile committed effective doses (CEDs) of the G2 groups were higher than those of the G1 groups for all four towns, although the between-group difference varied with the town. The highest CEDs were found in the G2 group of Futaba-town, and the lowest CEDs were in the Namie-town G1 group: 0.16 mSv and 0.04 mSv at the 90th percentile, respectively. The CEDs for both the G1 and G2 groups were relatively high for Okuma-town and Tomioka-town compared to those of the G1 group of Namie-town, although the former subjects were expected to be less exposed on 12 March 2011 and then evacuated to remote places, as did the residents of the other towns. (3) The CEDs of the G1 subgroup that evacuated outside Fukushima Prefecture were extremely low, suggesting that these subjects were little exposed on both 12 and 15 March 2011. However, the CEDs of the same G1 subgroup were rather higher than those of the corresponding G2 subgroup for Futaba-town and Okuma-town. We thus speculate that the WBC measurements were likely to have been affected by the contamination occurring in the second-round temporary re-entry (except for the Namie-town residents). (4) The analyses of the Namie-town evacuees indicated that the area including the middle and northern parts of Fukushima Prefecture was relatively more affected by the major release event on 15 March 2011. In conclusion, the early cesium intake due to the FDNPP accident remained detectable in the WBC measurements of certain present subjects; however, further analyses of the available data are necessary for a full understanding of the WBC measurement results.

中文翻译：

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福岛第一核电站附近城市疏散人员体内铯残留量与个体行为的关系。

为了支持对 2011 年福岛第一核电站 (FDNPP) 事故中遭受事故的居民的早期个人内部剂量的估计，我们尝试使用居住在 FDNPP 邻近城市的受试者的全身计数器 (WBC) 测量结果事故发生时。这些白细胞测量是在事故发生几个月后开始的；目标放射性核素是134Cs和137Cs。我们之前的研究分析了受放射线影响最严重的城市之一浪江町居民的个人残留Cs含量与事故发生后立即疏散行为之间的关系。这些结果表明，2011 年 3 月 12 日在 FDNPP 举行的第一次重大释放活动造成了重大暴露，特别是对那些当天推迟撤离的人。本研究扩大了范围，纳入了 FDNPP 附近的四个城镇（浪江、双叶、大隈和富冈）的受试者，以收集 2011 年 3 月 12 日发生的暴露事件的更多证据。此外，我们还调查了个体铯剂量之间的关系以及 2011 年 3 月 15 日最大的释放事件之后受试者的目的地。研究人群为 1,145 名成年人。我们首先根据距 FDNPP 的距离以及截至 2011 年 3 月 12 日 15:00 的疏散地点（25 公里边界）将受试者分为两个疏散组：G1 组（≥25 公里）和 G2 组（< 25 公里）。我们根据截至 2011 年 3 月 16 日 0:00 的受试者目的地，将这两个受试者组进一步分为七个亚组。我们的四个主要发现如下。(1)浪江町和双叶町G1组和G2组137Cs检出率存在显着性差异，而大隈町和富冈町则无显着性差异。这一结果与2011年3月12日下午的羽流通道（从西北向北流动）相对应，支持了我们之前的研究。(2) 所有四个城镇的 G2 组的上百分位数承诺有效剂量 (CED) 均高于 G1 组，尽管组间差异因城镇而异。双叶镇 G2 组的 CED 最高，而浪江镇 G1 组的 CED 最低：在第 90 个百分位数处分别为 0.16 mSv 和 0.04 mSv。与浪江镇 G1 组相比，Okuma 镇和 Tomioka 镇 G1 和 G2 组的 CED 都相对较高，尽管前受试者预计在 2011 年 3 月 12 日暴露较少，然后撤离到偏远的地方，其他城镇的居民也是如此。(3) 福岛县外撤离的G1亚组的CED极低，表明这些受试者在2011年3月12日至15日期间几乎没有受到暴露。然而，同一G1亚组的CED远高于相应的CED。双叶町和大隈町的 G2 小组。因此，我们推测WBC测量值很可能受到第二轮临时再入时发生的污染的影响（浪江町居民除外）。(4) 对浪江町避难人员的分析表明，福岛县中部和北部地区受 2011 年 3 月 15 日重大泄漏事件的影响相对较大。综上所述，FDNPP 事故导致的铯提前摄入在某些当前受试者的白细胞测量中仍然可检测到；然而，为了充分了解白细胞测量结果，需要对现有数据进行进一步分析。