Radon research and practice in Bulgaria – from retrospective measurements to mitigation

In Bulgaria there is a century-long tradition of radon measurements [8]. Since 1907 with hardly any interruption radon and later also radon progeny have been measured in mineral spas, in underground mines, in the human environment and in laboratory research. Experience from all these fields was gathered in the Faculty of Physics at St. Kliment Ohridski University of Sofia. Nowadays, exposure to 222Rn is considered the second most important cause for lung cancer among the population, after smoking [23]. Given its importance as a global health problem in the last decade a number of epidemiological studies of the population have been carried out [3, 5]. It was found that there is a statistically significant dose-response relationship between the risk and radon exposure even at average radon concentrations less than 200 Bq·m–3 [3]. In many countries the recommended action levels of radon concentrations, above which mitigation should be considered, are set close or equal to this value. There is a certain need for retrospective measurements, which are actually representative for the risk [4]. In Bulgaria, problems related to radon are among the main fields of research in the Laboratory of Dosimetry and Radiation Protection at Faculty of Physics, St. Kliment Ohridski University of Sofia. In this report our Radon research and practice in Bulgaria – from retrospective measurements to mitigation Dobromir S. Pressyanov