『Abstract
　Radon concentration and gamma activity concentration of naturally occurring radionuclides were determined and presented for two tourist caves (Karaca and Cal（Cにセディーユが付く） caves) in this study. These caves are reported to receive about 77,000 visitors during the summer season in 2007. It was seen that mean radon activity concentrations for the winter and summer seasons for the karaca cave is 1,023 and 823 Bq/m³ and for the Cal（Cにセディーユが付く） cave is 264 and 473 Bq/m³. Mean ²³⁶Ra, ²³²Th, and ⁴⁰K activity concentrations are found to be 43, 19, and 262 Bq/kg for the Karaca cave and 31, 27, and 460 Bq/kg for the Cal（Cにセディーユが付く） cave. Doses received by the cave guides due to radon were estimated to be 2.9 mSv/year for the winter season and 2.3 mSv/year for the summer season for the Karaca cave. Same values were estimated for the Cal（Cにセディーユが付く） cave, and the results were found to be 0.6 mSv/year for the winter season and 1.1 mSv/year for the summer season. Annual effective doses received by the visitors in both caves were estimated to be in the order of μSv/year because of the short exposure time comparing the cave guides. Although the reported values are below the recommended values, both groups are exposed to possible radiological risk during their stay inside the cave, since prolonged exposure to high radon concentration has been linked to lung cancer.

Keywords: Radon; Exposure; Cave; Turkey』

1. Introduction
2. materials and methods
　2.1. Karaca cave
　2.2. Cal（Cにセディーユが付く） cave
　2.3. Radon measurements
　2.4. Radioactivity measurement in soil
　2.5. Exposure dose estimation
3. Results and discussion
4. Conclusion
Acknowledgements
References