222Rn air concentration and radiation exposure levels in the Lantian Xishui karst cave of Shaanxi, China.

22Rn air concentrations in the Lantian Xishui karst cave of Shaanxi, China, were measured by continuous monitoring during a complete annual cycle (March 2004-February 2005) and annual doses for tour guides and visitors were estimated. The 22Rn air concentrations in the cave vary between a minimum of 383.6 Bq m(-3) and a maximum of 2,015.7 Bq m(-3), with an annual average of 1,100.4 Bq m(-3). Distinct seasonal variation of radon air concentrations inside the cave was observed. The maximum average radon concentration occurred in summer and the minimum average radon concentration occurred in winter. The annual effective dose to tour guides varies between an average of 1.2 mSv and 4.9 mSv depending on different equilibrium factors together with different dose conversion factors proposed in the literature, which is lower than the international recommendations. In all cases, the annual effective doses to visitors are well under the 1 mSv maximum suggested dose for a member of the public for one year.