Indoor radon measurements in the Beijing area.

Average indoor air radon concentration of 30 Bq/m3 was determined in various types of dwellings in the Beijing area using activated carbon detectors. In this study, several related factors were also investigated: radon area exhalation rates of 136 building materials and from soil surfaces; Ra-226 contents of 143 soil samples, 34 building materials and 28 coal samples; and radon concentrations in gaseous fuel, outdoor air and drinking water. The magnitude and relative importance of different sources in terms of indoor radon are discussed, compared and evaluated. The results show that the underlying soil and building materials are important sources of indoor radon. Cracks in floors or walls are major pathways for the entry of radon into houses. Measurements of the annual effective dose equivalent from radon daughters for different types of aboveground and underground buildings gave average values of 1.1 and 1.5 mSv, respectively.