The Mechanism Study of Radioactive Microparticles in the Body by Respiration and the Risk Assessment of Internal Exposure by using an Improved Model

根据去年曝光实验的结果，对222Rn和220Rn子体的沉积速度进行了测试，并与以前的研究进行了比较。结果表明，本研究的结果是可以接受的。基于CR-39的改进的被动222Rn/220Rn子体监测仪也在该系统中进行了校准，适用于住宅内222Rn和220Rn的照射评估。在改进的222Rn/220Rn子体监测仪研制的基础上，2018年在北京、长春、中国和日本青森进行了调查。使用校准的子体监测仪估算吸入暴露量，并分析室外PM2.5与室内222Rn和220Rn行为的相关性。结果表明，室内PM2.5浓度与EERC、EETC呈正相关，且EETC比EERC的相关性更强。这可能是由于周围环境中的颗粒物比室内的气溶胶源要大，可以通过自然通风和渗透进入室内。220Rn的子代比222Rn及其子代的半衰期相对较长。因此，220Rn子体更多地受到气溶胶沉积和附着过程的影响，与PM2.5浓度具有较强的相关性。未来，需要对包括室内和室外PM2.5暴露在内的环境因素进行更连续的测量，并需要考虑颗粒物的大小，以分析222Rn、220Rn和PM2.5暴露之间的关系。

Based on the results of the last year’s exposure experiment, a comparison of the testing of the deposition velocities of 222Rn and 220Rn progenies with previous studies was carried out. The results indicated that the results were acceptable in this research. An improved passive CR-39 based direct 222Rn/ 220Rn progeny monitor was also calibrated in this exposure system, which are suitable to assess the 222Rn and 220Rn exposure in dwellings. Based on development of the improved 222Rn/ 220Rn progeny monitor, a survey was carried out in Beijing, Changchun, China and Aomori, Japan in 2018. The inhalation exposure was estimated by using the calibrated progeny monitor, and then used to analyze the relevance of the outdoor PM2.5 to the behavior of indoor 222Rn and 220Rn. The result indicated which indicates that the indoor PM2.5 concentration performs positively correlated with EERC and EETC, and EETC is more correlated compared to EERC. It can be explained as the ambient particles whose sizes are larger than the indoor aerosol source, can enter indoor by natural ventilation and infiltration. The 220Rn progeny has a relatively longer half-life than the 222Rn and its progeny. Therefore, 220Rn progeny is more affected by the deposition and attachment process of aerosol, which performed stronger relevance to PM2.5 concentration. In the future, more continuous measurements on environmental factors include both indoor and outdoor PM2.5 exposure and particle size need to be considered to analyze the connection between 222Rn, 220Rn and PM2.5 exposures.