PRELIMINARY RESULTS OF INDOOR RADON SURVEY IN V4 COUNTRIES M. Mu ´´llerova ´ 1, *, K. Kozak 2 , T. Kova ´cs 3 , A. Csorda ´s 3 , D. Grzadziel 2 , K. Holy ´ 1 , J. Mazur 2 , A. Moravcsı ´k 1 , M. Neznal 4 , M. Neznal 4 and I. Smetanova ´ 5 1 Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska ´ dolina F-1, 841 04 Bratislava, Slovak Republic 2 Institute of Nuclear Physics PAN (IFJ PAN), Radzikowskiego 152, Krakow 31-342, Poland 3 Institute of Radiochemistry and Radioecology, University of Pannonia, Egyetem str. 10, Veszpre ´m 8200, Hungary 4 RADON v.o.s., Novakovych 6, 180 00 Praha 8, Czech Republic 5 Geophysical Institute, Slovak Academy of Sciences, Du ´bravska ´ cesta 9, 845 28 Bratislava, Slovak Republic *Corresponding author: mullerova@fmph.uniba.sk The measurements of radon activity concentration carried out in residential houses of V4 countries (Hungary, Poland and Slovakia) show that radon levels in these countries considerablyexceed theworld average. Therefore, the new radon data and statistical analysis are required from these four countries. Each partner chose a region in their own country, where radon concen- tration in residential buildings was expectedto be higher. The results of the surveycarried out in the period from March 2012 to May 2012 show that radon concentrations are <200 Bq m 23 in ∼87 %of cases. However, dwellings with radon concentration ∼800 Bq m 23 were found in Poland and Slovakia. It was also found that the distribution of radon frequency follows that of houses according to the year of their construction. INTRODUCTION On the basis of the newest research, it seems to be proved that the risk factor of lung cancer formation caused by radon is higher than previously known. Radon in homes causes ≏20 000 lung cancer deaths in the European Union (EU) each year (1) . This is ≏9 % of the total lung cancer deaths in the EU and ≏2 % of cancer deaths overall. The report (2) emphasizes that the national radon surveys carried out in European countries show large differences. Also in V4 countries, the performed measurements in residential houses confirmed that radon levels consid- erably exceed the Eastern Europe average ranging from 41 to 140 Bq m 23(3) . Therefore, new radon data and statistical analysis are required from these four countries. In the framework of the Visegrad Fund, small radon project entitled ‘Harmonization of deter- mining the radiation dose of the population originat- ing from radon’ has been carried out. Indoor radon measurements in houses were performed within this project. The object of the project was to elaborate a common measurement protocol for the Visegrad countries (Hungary, Poland and Slovakia) for meas- uring indoor radon concentrations (placement of detectors, type of detectors and questionnaires). The paper presents the preliminary results of the survey performed in the first period from March 2012 to May 2012. PLACES AND METHOD OF MEASUREMENTS Each participant of the project chose the areas in their own country (radon prone areas), where indoor radon concentration was possibly higher than average. Geological settings were one of the main reasons for indoor radon survey in studied lo- calities. The uranium and thorium content in soil and the information about soil radon activity con- centration were also relevant. The survey was per- formed in three localities: in Hungary: Veszpre ´m, Koma ´rom-Esztergon and Somogy; in Poland: Lo ´dz ´, Lublin and Krako ´w; in Slovakia: Bratislava, Mochovce and Ruz ˇomberok. The regions chosen for measurements in each country are shown in Figure 1. RADUET type detectors (Radosys Ltd, Hungary) were used for integrating measurement in indoor air. Allyl diglycol carbonate (CR-39) was used to detect the alpha particles emitted from radon and thoron as well as their progenies. The CR-39 foil was placed at the bottom of the chamber with sticky clays. Radon gas diffuses into the chamber through an invisible air gap between the lid and bottom of the chamber. Since this air gap functions as a high diffusion barrier, little thoron enters the chamber due to its very short half-life (55.6 s), compared with that of radon (3.82 d). In order to detect thoron more effectively, six holes of 6 mm in diameter are open at the side of the other chamber and are covered with an electroconductive sponge (4) . # The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com Radiation Protection Dosimetry (2014), pp. 1–4 doi:10.1093/rpd/ncu081 Radiation Protection Dosimetry Advance Access published April 10, 2014 at Univerzita Komenskeho on April 10, 2014 http://rpd.oxfordjournals.org/ Downloaded from