Kremena Ivanova This email address is being protected from spambots. You need JavaScript enabled to view it.1, Nina Chobanova1, Bistra Kunovska1, Jana Djounova1, Zdenka Stojanovska2 

1 National Centre of Radiobiology and Radiation Protection, Sofia, Bulgaria
2 Faculty of Medical Sciences, Goce Delcev University of Stip, Stip, Republic of North Macedonia

Received: July 22, 2022
Revised: September 28, 2022
Accepted: October 12, 2022

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

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Ivanova, K., Chobanova, N., Kunovska, B., Djounova, J., Stojanovska, Z. (2022). Exposure Due to Indoor Radon in Bulgarian Schools. Aerosol Air Qual. Res. 22, 220279.


  • Radon concentration was investigated in schools in one Bulgarian district.
  • The effects of indoor radon factors were considered.
  • Analysis was made by municipalities and premises according to their use and floors.
  • The high radon value, above 300 Bq m3 was measured in 30% of the school’s buildings.
  • The annual effective dose applying the ICRP methodology was calculated for students.


Indoor radon exposure is the largest contributor to population dose from natural sources. Radon as a natural radioactive gas could accumulate to harmful levels in buildings, such as homes and buildings with public access. In order to assess the exposure due to radon in school the results of indoor radon measurements in 55 state school buildings in 7 municipalities located in one district in southern Bulgaria are considered in this paper. The survey was carried out with passive CR-39 etched track detectors. Radon concentrations ranged from 17 to 868 Bq m–3, with a geometric mean of 117 Bq m–3 and a geometric standard deviation of 1.78. The findings revealed that in 30% of the measured buildings the radon concentration was higher than the national reference level of 300 Bq m–3. The statistically significant difference in indoor radon concentrations between municipalities (KW, р < 0.001) was obtained. The research was also focused on parameters affecting radon concentration levels such as type of room and floor location. The estimated annual effective dose of 0.39 to 1.07 mSv y1, applying the ICRP and UNSCEAR methodology, was calculated for students. The results of the measurements were provided to the administrative authorities and measures were proposed to improve the air in school buildings with high radon levels.

Keywords: Indoor radon, Schools, Detectors, Radon exposure, Effective dose

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