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Indoor radon concentrations were surveyed in 230 public schools in four Bulgarian districts for the period November/December 2019 to May/June 2020. The measurements were carried out in 2427 rooms on the basement, ground floor and first floor using the passive track detectors of the Radosys system. The estimated arithmetic and geometric means with standard deviations were 153 ± 154 and 114 Bq/m3 (geometric standard deviation (GSD) = 2.08), respectively. The results are higher than those referred from the National Radon Survey in dwellings. In 9.4% of the rooms, the radon concentrations were above the reference value of 300 Bq/m3. The difference between indoor radon concentrations in the districts was significant, which proves its spatial variation. The hypothesis that the applied energy efficiency measures increase indoor radon values in buildings was confirmed. The surveys demonstrated the importance of indoor radon measurements in school buildings, in order to control and reduce children's exposure. [ABSTRACT FROM AUTHOR]

The study presents the analysis of the results for indoor radon concentration in the kindergartens of two Bulgarian districts. The study presents the analysis of indoor radon concentration results in kindergartens of two Bulgarian districts. Measurements were performed with a passive method for the period from February to May 2015, in 411 children's rooms situated in 157 kindergartens. The measured radon concentrations in the children's rooms were between 10 and 1087 Bq per m. The evaluation of the results showed that in 10% of the kindergarten rooms, the radon concentration is above the national reference level of 300 Bq per m. The influence of the presence of a basement and the implementation of building renovation on the radon concentration were examined. The presence of a basement is a prerequisite for reducing the concentration of radon in the building. It has been proven that renovating the building increases the radon concentration in it. The analysis confirms the necessity of measuring the indoor radon concentration before the renovation and repair of the building, especially the implementation of energy efficiency measures. [ABSTRACT FROM AUTHOR]

The main contribution to population exposure is due to radon and thoron progenies and not radon itself. The aim of this study was therefore to estimate annual effective dose using the results of Direct Radon and Thoron Progeny Sensors were exposed in 69 selected schools and 319 dwellings in several regions of Balkans: in Serbia: regions of Sokobanja and Kosovo and Metohija, Republic of Macedonia, Republic of Srpska and Slovenia. Obtained average total effective doses are in the range from 0.22 mSv a−1 (schools in Republic of Srpska) to 2.5 mSv a−1 (dwellings in Kosovo) and are below the reference level of 10 mSv a−1 recommended by International Commission on Radiological Protection. [ABSTRACT FROM AUTHOR]

The indoor radon concentrations and lung cancer incidence in Eleshnitza village and Blagoevgrad district of Bulgaria were examined in the study reported here. The Eleshnitza was the second largest uranium mining and milling region of the country. The geometric mean of indoor radon concentration in Eleshnitza (465 Bq/m3) was higher than the geometric mean of Blagoevgrad district (78 Bq/m3). Retrospective analyses on lung cancer incidence, covering the period 1995–2012 have been shown the same trend. The results were suggestive of an existing relationship between the two variables. Possible effects attributable to age and gender on lung cancer incidence were examined and found to be significant. [ABSTRACT FROM AUTHOR]

As part of a survey on concentrations of radon, thoron and their decay products in different indoor environments of the Balkan region involving international collaboration, measurements were performed in 43 schools from 5 municipalities of the Republic of Macedonia. The time-integrated radon and thoron gas concentrations (CRn and CTn) were measured by CR-39 (placed in chambers with different diffusion barriers), whereas the equilibrium equivalent radon and thoron concentrations (EERC and EETC) were measured using direct radon–thoron progeny sensors consisting of LR-115 nuclear track detectors. The detectors were deployed at a distance of at least 0.5 m from the walls as well as far away from the windows and doors in order to obtain more representative samples of air from the breathing zone; detectors were exposed over a 3-month period (March–May 2012). The geometric mean (GM) values [and geometric standard deviations (GSDs)] of CRn, CTn, EERC and EETC were 76 (1.7), 12 (2.3), 27 (1.4) and 0.75 Bq m−3 (2.5), respectively. The equilibrium factors between radon and its decay products (FRn) and thoron and its decay products (FTn>0.5 m) were evaluated: FRn ranged between 0.10 and 0.84 and FTn>0.5 m ranged between 0.003 and 0.998 with GMs (and GSDs) equal to 0.36 (1.7) and 0.07 (3.4), respectively. [ABSTRACT FROM AUTHOR]

As a part of the systematic survey of indoor radon in Bulgaria, the indoor radon concentration was measured in 296 kindergarten buildings of Sofia city during 3 months (February to April 2013) using the CR-39 nuclear tract detectors. In 256 buildings at least two frequently occupied rooms (mainly playrooms) were observed. Altogether, 922 measurements were performed. The frequency distribution was well described by the lognormal function. The measured radon concentrations range between 9 and 1415 Bq m−3 with a geometric mean of 101 Bq m−3 (2.08) and an arithmetic mean 132 Bq m−3 with a standard deviation of 118 Bq m−3. The radon concentrations obtained in this survey were compared with that in Sofia city dwellings obtained from a previous study. A detailed statistical analysis of the building factors was presented. [ABSTRACT FROM AUTHOR]

The first systematic indoor radon survey in four districts of Bulgaria was performed. Three hundred and seventy-three selected ground floor dwellings were measured using the nuclear track detectors during 6 months, from October 2011 to May 2012. It was found that indoor radon concentration varied between 20 and 3560 Bq m−3 with median value of 90 Bq m−3. The fractions of dwellings in four districts: Sofia city, Sofia districts, Plovdiv and Varna above the reference levels of 300 Bq m−3 were 3, 9, 14 and 5 %, respectively. Each data set does not follow a log–normal distribution at a significance level of 95 %. The results of the analysis of the variance showed statistically significant differences among the indoor radon concentrations for the regions between urban and rural municipalities as well for the building with and without basement. These results may be utilised to set up the methodology for a more systematic survey in Bulgaria. [ABSTRACT FROM PUBLISHER]

The authors present the results of a year-long survey of the indoor radon concentration levels in the FYR of Macedonia. A total number of 437 dwellings in eight statistical regions were subject to radon concentration measurements by using CR-39 track detectors. The annual mean indoor radon concentration in each measuring site was estimated from the four individual measurements with 3 months duration. The measuring period was from December 2008 to December 2009. The distribution of the results was nearly log–normal. The arithmetic and geometric mean values of the annual mean value of radon concentration were estimated to be 105±84 and 84*/1.9 Bq m−3, respectively. The annual effective dose due to indoor exposure to radon in the dwellings was estimated to be 2.1*/1.9 mSv y−1. [ABSTRACT FROM PUBLISHER]