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

基于去年的暴露实验结果，将222Rn和220Rn子代的沉积速度测试与之前的研究进行了比较。结果表明，本研究结果是可以接受的。采用改进的基于CR-39的被动直接222Rn/ 220Rn子代监测仪进行了标定，该监测仪适用于住宅环境中222Rn和220Rn的暴露评估。在研制改进型222Rn/ 220Rn后代监测仪的基础上，于2018年在中国北京、长春和日本青森进行了调查。通过校准后的子代监测仪估算吸入暴露量，然后分析室外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和EETC呈正相关，且EETC的相关性强于EERC。这可以解释为比室内气溶胶源粒径大的环境颗粒通过自然通风和渗透进入室内。220Rn子代的半衰期比222Rn及其子代的半衰期要长。因此，220Rn子代更受气溶胶沉积和附着过程的影响，与PM2.5浓度的相关性更强。在未来，需要考虑更多的环境因素的连续测量，包括室内和室外PM2.5暴露和粒径，以分析222Rn， 220Rn与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.