Journal of Materials Science and Engineering A 5 (9-10) (2015) 339-346 doi: 10.17265/2161-6213/2015.9-10.002 Measurements of Environmental Radon Activity Concentration Outdoors in Bosnia and Hercegovina Alma Damjanovic 1 , Jasmin Adrovic 2 , Zejnil Tresnjo 3 and Feriz Adrovic 2* 1. The International School of The Hague, 2505 CA 2505 CA The Hague, The Netherlands 2. University of Tuzla, Faculty of Natural Sciences and Mathematics, Univerzitetska 4, Tuzla, Bosnia and Herzegovina 3. University Dzemal Bijedic of Mostar, Sjeverni logor bb, 88104 Mostar, Bosnia and Herzegovina Abstract: Radon is a unique natural element because it is an inert gas and at the same time radioactive in all of its isotopes. It is known fact that exposure of the population to high concentrations of radon gas, leads to irradiation of primarily respiratory organs, which can cause lung cancer. For reliable prospecting of radon activity concentration in the living environment, the first input parameter is the concentration of outdoor radon in the air. This paper presents the results of a three-year research of radon activity concentration in the air of Bosnia and Herzegovina. At the measurement locations were registered daily and seasonal variations of the outdoor radon concentrations, whose average values were in the range of 15-38 Bq/m 3 . They were measured with Alpha GUARD PQ 2000 radon portable measuring system (Genitron Instruments - Frankfurt). Key words: Radon activity concentration, outdoor exposures, Bosnia and Herzegovina. 1. Introduction One of the middle members of each natural series is the isotope of the noble gas radon: 222 Rn, 220 Rn and 219 Rn with the disintegration half-time of 3825 days, 55.6 s and 3.96 s respectively. Their immediate predecessors are radium isotopes which decompose into radon by -decay. Because of the very short half-life, as well as for the concentrations ratio 235 U/ 238 U in the nature, which is 0.00719, the isotope 219 Rn can be ignored, while the isotope 220 Rn is of less importance due of its short half-life [1]. Because of the longest lifetime and isotopic abundance, the greatest importance of the natural isotopes of radon has 222 Rn and the term radon will refer to this isotope. In its decay series, radon gas over its short-lived decay progeny is transformed into stable lead 206 Pb, emitting 5 alpha particles of energy up to 7.7 MeV, beta radiation energy up to 2.8 MeV and gamma-ray photon energy up to 2.4 MeV [2]. * Corresponding author: Feriz Adrovic, full professor, research field: nuclear physics. The concentration of radon in the air is variable and depends on a number of meteorological parameters. Due to the relatively long half-life (3.82 days), radon can stay relatively long in the atmosphere before it decays. So it takes part in the turbulent transfer through the atmosphere and can reach to its higher layers, and travel long distances. Also, seasonal changes in meteorological conditions affect the variation of radon concentration in air, as well as the concentration of natural radioactivity of air in general. The degradation products of radon and thoron in most cases are positively charged, from 80% to 85% of them, and are chemically active [2]. They interact with negative ions present in the atmosphere and in the process of exchanging charges there occurs their attachment to natural aerosols. This is the origin of naturally occurring radioactive aerosols. Increased relative humidity creates favorable conditions for increased condensation of water vapor and sorption of radioactive decay products as emanation of the particles of water vapor. The resulting active aerosols D DAVID PUBLISHING