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

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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.