Note INITIAL INVESTIGATION OF 222 Rn IN THE TBILISI URBAN ENVIRONMENT S. Pagava,* V. Rusetski,* Z. Robakidze,* E. B. Farfán, † R. E. Dunker, ‡ J. L. Popp, ‡ M. Avtandilashvili, ‡ D. P. Wells, § and E. H. Donnelly** Abstract—Georgia has geological formations with high ura- nium content, and several buildings are built with local materials. This can create potentially high radon exposures. Consequently, studies to mitigate these exposures have been started. This study presents a preliminary investigation of radon in Tbilisi, the capital of Georgia. An independent radiological monitoring program in Georgia has been initiated by the Radiocarbon and Low-Level Counting Section of I. Javakhishvili Tbilisi State University with the cooperation of the Environmental Monitoring Laboratory of the Physics/ Health Physics Department at Idaho State University. At this initial stage the E-PERM systems and GammaTRACER were used for the measurement of gamma exposure and radon concentrations in air and water. Measurements in Sololaki, a densely populated historic district of Tbilisi, revealed indoor radon ( 222 Rn) concentrations of 1.5–2.5 times more than the U.S. Environmental Protection Agency action level of 148 Bq m 3 (4 pCi L 1 ). Moreover, radon-in-air concentrations of 440 Bq m 3 and 3,500 Bq m 3 were observed at surface borehole openings within the residential district. Measurements of water from various tap water supplies displayed radon con- centrations of 3–5 Bq L 1 while radon concentrations in water from the hydrogeological and thermal water boreholes were 5–19 Bq L 1 . In addition, the background gamma absorbed dose rate in air ranged of 70 –115 nGy h 1 at the radon test locations throughout the Tbilisi urban environment. Health Phys. 95(6):761–765; 2008 Key words: radon; dose; electrets; 222 Rn INTRODUCTION POTENTIALLY HIGH radon exposures are possible in Georgia because of its geological formations. This study presents a preliminary investigation of radon concentrations in Tbilisi, Georgia. During the summers of 2003 and 2004, cooperative investigations and expeditions in the Repub- lic of Georgia took place with scientists from the Radio- carbon and Low-Level Counting Section (R&LLC) of I. Javakhishvili Tbilisi State University (TSU) and the Environmental Monitoring Laboratory (EML) of the Physics/Health Physics Department at Idaho State Uni- versity (ISU). This early work revealed the lack of available information and resources throughout Georgia to access potential environmental radiation hazards. Based on the results of this study, the participants recognized a substantial need to expand the survey of the radiological hazards in Georgia and present valuable information for the people of Georgia. The necessary equipment was loaned to the R&LLC by the EML. Measurements of radon in air, water, and gamma exposures were made in the Tbilisi urban environ- ment. The data collected is used by the non-governmental organization “Radioecology-XXI,” founded by the R&LLC researchers, to inform the population about the possible health risk from radon and other sources of ionizing radiation, locations where remedial action or further moni- toring is recommended, and adequate prevention and reme- diation measures. BACKGROUND Tbilisi, the capital of Georgia, has a population of approximately 1.5 million and is situated in an active seismo-tectonic zone, characterized by numerous hot springs and medicinal bathhouses. Thermal waters within the Tbilisi Hydrothermal Field originate in volcanic rocks that are enriched in uranium compared to normal soils. Hence, the radon content of these thermal waters may be higher than background. * Radiocarbon and Low-Level Counting Section of I. Javakhish- vili Tbilisi State University, 3, I. Chavchavadze Avenue, Tbilisi, 0128, Georgia; † Savannah River National Laboratory, Environmental Sci- ence and Biotechnology, 773-42A, Savannah River Site, Aiken, SC 29808; ‡ Idaho State University, Department of Physics/Health Phys- ics, Campus Box 8106, 785 South 8th Avenue, Pocatello, ID 83209; § Idaho Accelerator Center, 150 Alvin Ricken Drive, Pocatello, ID 83201; ** Centers for Disease Control and Prevention, 4770 Buford Highway, NE, MS F03, Atlanta, GA 30341. For correspondence contact: Eduardo B. Farfán, Environmental Science and Biotechnology, Savannah River National Laboratory, Savannah River Nuclear Solutions, Savannah River Research Campus (999-W/360), 227 Gateway Drive, Aiken, SC 29803, or email at Eduardo.Farfan@srnl.doe.gov. (Manuscript accepted 10 May 2008) 0017-9078/08/0 Copyright © 2008 Health Physics Society 761