Indoor radon concentration and public dose evaluation in Ningxia Hui Autonomous Region, China

The indoor radon concentration in a total of 143 rooms from 82 urban and 61 rural households in Ningxia was measured using the solid nuclear track method over four quarters for 1 y, followed by calculation of the annual effective dose. The results indicated that the mean of indoor radon concentrations was 88 Bq m-3, with a range from 39 to 226 Bq m-3. The concentrations exceeded 100 Bq/m-3 in 30% of the measurement locations, with two points measuring above 200 Bq/m-3, accounting for 1.4%. The indoor radon concentration was higher in rural areas compared to urban areas. Moreover, it exhibited a seasonal variation, with the highest levels observed during winter and the lowest during summer. Additionally, the effective dose of indoor radon among residents in Ningxia was calculated at 2.20 mSv a-1.