Outdoor radon concentration in China

The annual effective dose to Chinese population from natural radiation exposure is about 3.1 mSv/y, of which 1.56 mSv/y or 50% is due to the exposure from radon and its daughters [1]. The enhanced natural radiation level results mainly from indoor radon concentrations rising by 70%, compared to the previous data in 1990s [1, 2]. Based on the research, the increase in indoor radon concentrations was resulted from the building materials of the dwellers and the change in ventilation. Outdoor radon concentrations may also increase as rapid industrial development in China in the past 20 years. As a result, large amount of radon was released because of the consumption of coals, oil and gas, as well as exploitation of land. During the period from 1983 to 1998, two national radon survey were carried out by the National Health Authority and the National Environmental Authority, respectively [3–6]. Three large-scale indoor radon survey were conducted by difference institutions, the fi rst one in 26 cities from 2002 to 2005 [7], the second one in 5 provincial cities and 12 prefectural-level cities from 2 006 to 2010 [8] and the third one in 11 provincial cities from 2013 to 2014. In addition, some local governments and institutes conducted radon concentration surveys too [9, 10]. In contrast to the work done on indoor radon concentration surveys, much less were Outdoor radon concentration in China Qifan Wu, Ziqiang Pan, Senlin Liu, Chunhong Wang