Volcanic tuff stones are widely used to coat the interior and exterior surfaces of buildings for ornamental purposes in the construction industry in Turkey, and are also used as structural material in the construction of masonry buildings, especially in the Cappadocia region, which is a popular tourist destination. In this study, seventy-six volcanic tuff stone samples collected from different quarries located in different geographical regions in Turkey were surveyed for radiometric analysis, and the radiological risk to human health caused by ionizing radiation from natural radionuclides in the volcanic tuff stone samples was evaluated. The activity concentrations of 238 U, 232 Th, 226 Ra and 40 K analyzed in volcanic tuff stone samples were very variable, ranging from 3 to 389, 8 to 401, 2 to 263 and 99 to 2107 Bq kg −1 , respectively. The emanation coefficient and mass exhalation rate of 222 Rn measured for the volcanic tuff samples ranged from 2 to 68% with an average of 34%, and 1 to 194 μBq kg −1 s −1 with an average of 43 μBq kg −1 s −1 , respectively. The external (gamma) and internal (alpha) hazard indices, indoor absorbed gamma dose rate and the corresponding annual effective dose were estimated to evaluate the potential radiological risk to human health. The results showed that all of the surveyed volcanic tuff stone samples can be used as covering building materials for ornamental or insulating covering purposes. However, the use of some volcanic tuff stone samples as structural building materials should be restricted. Keywords: natural radioactivity / radon mass exhalation rate / emanation coefficient / hazard indices / annual effective dose / radiological risk / volcanic tuff 274Ş. Turhan et al.: Radioprotection 50(4), 273-280 (2015) Table 1. Information on the locations of quarries, sample codes and sample colors. Quarry code N • Sample colors (number of samples) Quarry place (geographical region) Q1 6 Yellow (2), black (1), cherry (1), dark gray (1), dusty-rose (1) Kayseri-Tomarza (Central Anatolia) Q2 6 Yellow (2), brown (1), black (1), dusty-rose (2) Kayseri-Tomarza (Central Anatolia) Q3 7 Cherry (1), red (1), brown (1), yellow (1), gray (1), dusty-rose (1), black (1) Kayseri-Tomarza (Central Anatolia) Q4 7 Gray (4), black (1), dusty-rose (1), brown (1) Kayseri-Tomarza (Central Anatolia) Q5 4 Yellow (3), brown (1) Kayseri-Tomarza (Central Anatolia) Q6 6 Yellow (1), black (1), gray (1), dusty-rose (1), fawn (1), dark brown (1) Kayseri-Develi (Central Anatolia) Q7 4 Gray (4) Kayseri-Melikgazi (Central Anatolia) Q8 3 Gray (2), yellow (1) Kayseri (Central Anatolia) Q9 6
