Radiation exposure due to Rn, Rn and their progenies in three metropolises in China and Japan with different air quality levels.

Radiation exposure due to radon contributes most of the ionizing radiation exposure to people among natural radiation sources. This research measured the Rn, Rn by the RADUET and their progeny concentrations by the improved deposition based Rn and Rn progeny monitor, and the contribution of outdoor PM concentrations to indoors by a modified steady-state mass balance model in Beijing, Changchun, China and Aomori, Japan. Based on these results, we preliminarily explored the relevance between the city level outdoor PM exposure and indoor Rn, Rn inhalation exposure in these three metropolises with different air quality levels. The average equilibrium equivalent radon concentration (EERC) and equilibirum equivalent thoron concentration (EETC) indoor were 17.2 and 1.1 Bq m in Beijing, 19.4 and 1.3 Bq m in Changchun, and 10.8 and 0.9 Bq m in Aomori, respectively. The indoor EERC and EETC in Beijing showed 1.4 and 2.2 times as high as that measured in 2006. The indoor radiation dose due to inhalation presented in a descending order as Changchun, Beijing and Aomori, which were in accordance with their outdoor Rn concentrations. The indoor radiation doses due to Rn contributed 30% of the total dose in the three cities, indicating that Rn cannot be neglected when evaluating indoor radiation dose. It should be noted that, the indoor PM concentrations of outdoor origin presented strong correlation (r = 0.772) with indoor EETC and moderate correlation (r = 0.663) with indoor EERC, indicating that the PM of outdoor origin can break the concentration balance of the indoor PM, then affect the indoor Rn and Rn behaviors, and further affect the inhalation exposure of radon.