Investigation of the indoor (222)Rn and (220)Rn levels in the residential environment and estimation of the annual effective radiation dose for ordinary residents

To evaluate the health risk of radon and its progeny, a large amount of accurate monitoring data is needed according to the theory and practice of health risk assessment. However, the indoor radon levels in different regions in China and worldwide reveal temporal and spatial variations. In addition, the residents living in different areas follow distinct living modes. Therefore, it is recommended and accepted by many researchers to detect the radon level in local areas and subsequently conduct health risk assessments based on local detection data. In this study, 21 bedrooms of households in Weifang city were selected, and the indoor (222)Rn and (220)Rn levels were detected with RAD7 radon detector in winter, while the annual effective radiation dose was calculated for ordinary residents in Weifang city. Our investigation showed that the 24- and 12-hour average levels of (222)Rn were 35.7±15.2 Bq/m(3) and 36.2±15.8 Bq/m(3), respectively. The 24- and 12-hour average levels of (220)Rn were 30.4±12.3 Bq/m(3) and 22.4±11.6 Bq/m(3), respectively. There were significant differences in the average levels of (222)Rn and (220)Rn between floors. The estimated annual effective radiation dose received by ordinary residents in Weifang city was 1.7193 mSv, of which 0.9479 mSv originated from (222)Rn and its progeny and 0.7714 mSv originated from (220)Rn and its progeny, accounting for 55.1% and 44.9%, respectively, of the total dose. Our findings suggest that (220)Rn should not be ignored by local residents in Weifang city, and more attention should be paid to (220)Rn in future research.