Seasonal variations of indoor radon concentrations: a study across different climate zones in China

This study investigated the seasonal variations of indoor radon concentrations in parts of cities across different climate zones of China. Using solid state nuclear track detectors (SSNTDs), radon measurements were conducted over a 12-month period in 171 dwellings located in 15 provincial capital cities. The annual average indoor radon concentration was 81 Bq m−3, with the highest mean level recorded in the Severe Cold Area (99 Bq m−3) and the lowest in the Hot Summer Warm Winter Area (52 Bq m−3). A consistent seasonal pattern was observed across all zones, characterized by elevated concentrations in autumn and winter and lower levels in spring and summer. The mean winter-to-summer concentration ratio was 1.68, indicating a declining trend compared to earlier data from 1994 in China. This trend may be attributed to changes in ventilation practices associated with the widespread adoption of air conditioning. Seasonal correction factors were determined for different climate zones, ranging from 0.80 to 1.43. This study highlights the seasonal fluctuations of indoor radon and the necessity of applying appropriate correction factors when estimating annual average radon concentrations based on short-term measurements to reduce assessment bias. The findings provide critical data and a methodological foundation for accurately assessing and seasonally correcting indoor radon concentrations under diverse climatic conditions in China.