Natural radiation levels in Fu’an city in Fujian Province of China Y. Luo a , W. Zhuo b, * , M. Wei a , S. Tokonami b , W. Wang a , Y. Yamada b , J. Chen a , M. Chen a a Fujian Centre for Prevention and Control of Occupational Diseases and Chemical Poisoning, P.R. China b Radon Research Group, National Institute of Radiological Sciences, Chiba 263-8555, Japan Abstract. A survey of natural radiation levels was performed in an area with the highest mortality of lung cancer in Fujian Province of China. Even though relatively high terrestrial gamma radiation was observed, the concentrations of indoor 222 Rn, 220 Rn and its progeny are near the same as the provincial averages. Annual arithmetic mean concentrations of indoor 222 Rn, 220 Rn and its progeny were 29, 184 and 0.8 Bq m À3 , respectively. The public exposure to radon and thoron is estimated to be 1.2 mSv year À1 , similar to the world average. D 2004 Elsevier B.V. All rights reserved. Keywords: Radon; Thoron; Equilibrium-equivalent thoron concentration; Gamma dose rate 1. Introduction Fu’an city populated with about 600,000 people locates in the eastern part of Fujian Province in China. Based on the Cancer Registry of Fujian Province, although the total cancer mortality in Fu’an city was not high, the mortality of lung cancer was the highest in the past decades. The reason is still unknown so far. On the other hand, very high content of 232 Th in soil was reported in the area [1], it is expected that high thoron might exist in the area. In this study, a survey of the natural radiation levels was carried out, their results are reported. 2. Materials and methods Indoor 222 Rn and 220 Rn were measured by the passive integrating 222 Rn and 220 Rn discriminative monitor [2]. The monitors were set at about 10 cm from a wall in a bedroom. The equilibrium-equivalent thoron concentration was estimated from measuring the deposition rate of its progeny [3]. The deposition rate monitors were set in the middle 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.09.048 * Corresponding author. Tel.: +81 43 206 3111; fax: +81 43 206 4098. E-mail address: whzhuo@nirs.go.jp (W. Zhuo). International Congress Series 1276 (2005) 311 – 312 www.ics-elsevier.com