In this paper the results of radon concentration measurements performed in 207 schools in 7 communities of Southern Serbia are presented. The annual radon concentration varied from 17 Bqm-3 to 428 Bq m-3 with a median value of 96 Bq m-3. The arithmetic mean (AM) of the 207 annual averages was 118 Bq m-3 with a standard deviation (SD) of 78 Bq m-3. The best distribution fitting of radon concentration by log-normal function was obtained. The log-normal parameters are the following: geometric mean (GM) = Bq m-3, geometric standard deviation (GSD) = 1.9. In addition, a spatial distribution of the indoor radon concentration over the investigated areas is observed.JRC.E.8-Nuclear securit

ANTIGNANI Sara

BOCHICCHIO Francesco

BOSSEW Peter

CARELLI Vincio

CARPENTIERI Carmen

CORDEDDA C.

CUKNIC Olivera R.

FILIPOVIC J.

STOJANOVSKA Zdenka

TOLLEFSEN Tore

VESELINOVIC Nenad C.

ZUNIC Zora S.

JRC Publications Repository

SOME RESULTS OF A RADON SURVEY IN 207 SERBIAN SCHOOLS* 
Z. S. ZUNIC1, C. CARPENTIERI2, Z. STOJANOVSKA3, S. ANTIGNANI2, N. VESELINOVIC1,  
T. TOLLEFSEN4, V. CARELLI5, C. CORDEDDA5, O. CUKNIC6, J. FILIPOVIC1, P. BOSSEW7,  
F. BOCHICCHIO2 
1Institute of Nuclear Sciences “Vinca”, P.O Box 522, 11000, University of Belgrade, Serbia 
2Italian National Institute of Health, Viale Regina Elena 99, 00161 Rome, Italy 
3Faculty of Medical Sciences, Goce Delcev University, Stip, FYR of Macedonia 
4European Commission, DG JRC, Institute for Transuranium Elements, Ispra, Italy 
5Safety and Environment Department, Telecom-Italia S.p.A., Rome, Italy 
6Public Company “Nuclear Facilities of Serbia”, Vinca, M. P. Alasa 12-14, Belgrade, Serbia 
7Bundesamt für Strahlenschutz, Köpenicker Allee 120-130, 10318 Berlin, Germany 
Received November 15, 2012 
In this paper the results of radon concentration measurements performed in 207 schools 
in 7 communities of Southern Serbia are presented. The annual radon concentration 
varied from 17 Bqm-3 to 428 Bq m-3 with a median value of 96 Bq m-3. The arithmetic 
mean (AM) of the 207 annual averages was 118 Bq m-3 with a standard deviation (SD) 
of 78 Bq m-3. The best distribution fitting of radon concentration by log-normal 
function was obtained. The log-normal parameters are the following: geometric mean 
(GM) = 97 Bq m-3, geometric standard deviation (GSD) = 1.9. In addition, a spatial 
distribution of the indoor radon concentration over the investigated areas is observed. 
Key words: indoor radon, primary schools, Southern Serbia, CR-39 detectors, radon map.  
1. INTRODUCTION 
Since many countries started to conduct their national programs on radon in 
dwellings around 1970, surveys using radon measurements in schools and 
kindergartens have also been performed in a number of countries throughout the 
world. In Europe, radon surveys have been carried out in schools in Slovenia [1], in 
Greece [2, 3], in Italy: the Salento peninsula in Southeast Italy [4], in Eastern Sicily 
[5], in the Neapolitan area [6], and in the province of Parma [7]. Out of all 
investigations in Europe, the highest number of schools included in a survey, more 
than 4.000, was achieved in Ireland [8]. In other parts of the world, the radon 
concentration in schools have also been investigated, such as in Jordan’s capital 
Amman [9], and in Nigeria in the Oke-Ogun area [10]. 
 
* Paper presented at the First East European Radon Symposium – FERAS 2012, September 2–5, 
2012, Cluj-Napoca, Romania. 
Rom. Journ. Phys., Vol. 58, Supplement, P. S320–S327, Bucharest, 2013 
2 Some results of a radon survey in 207 Serbian schools 
 
S321 
In Serbia, over the period 2008–2010, a systematic survey of radon 
concentration in schools was conducted, covering all primary schools in mainly 
rural communities of Southern Serbia (Figure 1). This paper deals with the results 
of field activities encompassing 207 primary schools over the 7 communities, 
within two districts [11]. The survey was carried out through an international 
collaboration between scientists from several institutes, namely, the Vinca Institute 
of Nuclear Sciences, Serbia (that initiated, coordinated and made field activities); 
the National Institute of Health, Rome, Italy; the Safety and Environment 
Department of Telecom-Italia; the German Federal Office for Radiation Protection; 
and the Joint Research Centre of the European Commission [12]. Aiming at further 
continuation of a systematic radon concentration survey in primary schools of 
Southern Serbia [11, 12], encompassing 207 new schools, the main goals of this 
work were: to evaluate radon exposure of children and teachers in these primary 
schools; to improve the knowledge of radon distribution in Serbia also by 
evaluating the extent to which primary schools can be considered acceptable 
“radon proxies of residential buildings” and potentially to contribute to the 
European Atlas of Natural Radiation. 
 
 
Fig. 1 – Spatial estimate of annual average radon concentration in 207 schools. 
 Z.S. Zunic et al. 3 
 
S322 
2. MATERIALS AND METHODS 
In two (Lebane and Crna Trava) of the seven communities investigated,  
CR-39 detectors were exposed for one year. In the other five communities (Figure 1), 
the detectors were exposed in rooms side-by-side for two consecutive six-months 
periods, starting in March/May 2009 and ending in March/May 2010. The pairs of 
CR-39 detectors have been deployed in classrooms on ground floor, teacher’s or 
director’s rooms. For each school, GPS coordinates were recorded. The 
measurement points of the detectors were on shelves and cupboards mostly, or on 
the wall directly. After being etched, the detectors were analyzed using a fully 
automated image analysis (read-out) system, the Politrack one, operating with 
software Politrack version 4.1 (produced in Italy). System calibration was obtained 
in the radon chambers of the UK Health Protection Agency and the Italian National 
Metrology Ionising Radiation Institute (INMRI) [12]. For each school, the annual 
average radon concentration of the monitored rooms was calculated. 
3. RESULTS AND DISCUSSION 
Summary statistics of indoor radon measurements in schools are presented in 
Table 1. Out of the 207 schools under investigation, valid measurements were 
performed in 167 schools for the first six months period of exposure, and in 166 
schools for the second one. In two communities with 38 schools total, the detectors 
were exposed for one 12 consecutive months. 
Table 1 
 Descriptive statistics of indoor radon concentrations measured in: 1st six-months period,  
2nd six-months period and one year (a single 12-months period). In the last column are the parameters 
of the annual average for measurements in all the 207 measured schools 
Parameter 1
st six-months 
 period 
2nd six-months 
 period 
12-months 
period 
Annual 
average 
No. of measurements 167 166 38 207 
Minimum (Bq m-3) 17 29 17 17 
Median (Bq m-3) 92 112 78 96 
Maximum (Bq m-3) 363 492 303 428 
Arithmetic mean (Bq m-3) 118 130 95 118 
Standard deviation (Bq m-3) 81 83 72 78 
Standard error (Bq m-3) 6 6 12 5 
Geometric mean (Bq m-3) 94 108 76 97 
Geometric standard deviation 2.0 1.9 1.9 1.9 
Skewness 1.2 1.5 1.7 1.3 
Kurtosis 0.7 2.7 2.0 1.4 
The ratio between radon concentrations measured in the first and second 
periods was analyzed in order to obtain correction factors for schools where 
measurements have been carried out for only one six-months period. At the 95% 
level of significance, the decision was not to reject the null hypothesis. The ratio 
4 Some results of a radon survey in 207 Serbian schools 
 
S323 
within the communities follows a normal distribution (Anderson-Darling Test at 
p > 0.05). The arithmetic mean values of the ratio of radon concentration both for 
the first and the second period for 5 communities are shown in Figure 2. If there 
were – for some reason – missing measurements and results in one of the periods, 
the annual radon concentration was estimated using the obtained ratio. For these 
schools, the values measured in the first (or second) period were divided (or 
multiplied) by the value (arithmetic mean) for the communities reported in Figure 
2. The results of the annual mean radon concentration for a particular school was 
an arithmetic mean of the measurements performed in both periods. 
 
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
 Bujanovac Surdulica  Vladicin
Han
 Vlasotince  Vranje All
ra
tio
 
Fig. 2 – The arithmetic mean value of the ratio between radon concentrations measured in the two 
periods in the Bujanovac, Surdulica, Vladicin Han, Vlasotince and Vranje communities. 
Distribution of annual radon concentration fitted log-normal distribution 
(Figure 3, left). The log-normality as well normality of log-transformed data 
(Figure 3, right) was confirmed with Kolmogorov-Smirnov and Chi-square 
goodness-of-fit test between observed and theoretical frequencies (p > 0.05). 
 
 
Fig. 3 – Distribution of annual radon concentration fitted log-normal distribution (left)  
and log-transformed data fitted normal distribution (right). 
Taking into account the log-normality of the data, the log-transformed data 
were considered in the statistical analysis. Because of non-homogeneity of 
 Z.S. Zunic et al. 5 
 
S324 
variances of data in the communities (Bartlett test, p = 0.007), the Kruskal-Wallis 
test was applied to test for differences in radon concentration. The test results 
showed statistically significant differences between the mean concentrations of the 
communities at 95% confidence level (p = 0.0002). Descriptive statistics of annual 
radon concentration in all 7 communities are given in Table 2. 
Table 2 
Descriptive statistics of annual radon concentration for field site 
Field site 
 Bujanovac Crna 
Trava 
Lebane Surdulica Vladicin 
Han 
Vlasotince Vranje All 
N 39 6 26 18 23 35 60 207 
Min.  30 51 17 47 31 47 30 17 
Median  112 114 63 132 175 93 82 96 
Max.  338 217 212 428 310 227 359 428 
AM  127 118 69 156 158 101 118 118 
SD  72 58 38 101 79 43 90 78 
SE  12 24 8 24 17 7 12 5 
GM  109 106 60 130 134 94 91 97 
GSD 1.8 1.7 1.7 1.9 1.9 1.5 2.1 1.9 
N = number of schools; AM = Arithmetic Mean (Bq m-3); SD = Standard Deviation (Bq m-3); 
SE = Standard Error (Bq m-3); GM = Geometric Mean (Bq m-3); GSD = Geometric Standard Deviation. 
 
For further evaluation, the non-parametric Mann-Whitney U test was applied 
to determine the differences between mean values in the communities (differences 
are significant with p < 0.05). The Lebane community revealed significantly lower 
radon concentration than Bujanovac (MW, p < 0.0001), Crna Trava (MW,  
p = 0.026), Surdulica (MW, p =0.0004), Vladicin Han (MW, p < 0.0001) Vlasotice 
(MW, p = 0.001) and Vranje (MW, p < 0.031) (Figure 4). On the same figure, no 
significant difference between radon concentrations in: Bujanovac and Crna Trava 
(MW, p = 0.92), Surdulica and Vladicin Han (MW, p = 0.703), Vlasotince and 
Vranje (MW, p = 0.576), were obtained. 
 
3.8
4.0
4.2
4.4
4.6
4.8
5.0
5.2
 Bujanovac Crna Trava  Lebane Surdulica  Vladicin
Han
Vlasotince Vranje
ln
 C
R
n (
B
q 
m
-3
).
 
Fig. 4 – The natural logarithm of radon concentration in the 7 communities  
(error bars represent the standard error). 
6 Some results of a radon survey in 207 Serbian schools 
 
S325 
In addition, we compare our results with radon concentration in schools 
reported for some other European countries, shown in Table 3.  
Table 3 
Comparison of the results of indoor radon surveys in schools between Serbian results  
and other European surveys 
Country No of Regions 
No of schools/ 
kindergartens 
Range of radon 
conc. (Bq m-3) Reference 
Greece 8 512 69–177 [2] 
Italy (S-E Italy) 1 438 21–1608 [4] 
Italy (Parma) 1 49 10–108 [7] 
Italy (Neapolitan area) 1 30 144* [6] 
Slovenia  18/7 145–749/ 70–770 [1] 
Serbia 2 207 17–428 Present work 
*average value 
 
For the present survey, the influence of floor levels on the radon 
concentrations in the different communities was investigated. The schools were 
classified into three groups: ground floor, mezzanine (means that the room is 
accessed over a few steps from actual ground level) and first floor. ANOVA test 
shows that rooms at the ground floor and mezzanine have significantly (p = 0.005) 
higher geometric mean of radon concentration than rooms at the first floor (Figure 5).  
 
Fig. 5 – Mean ln(CRn) in communities grouped by floor level. 
In order to estimate the annual effective dose E (mSv y–1) expected to be 
received by the pupils and teachers due to exposure to indoor radon and its decay 
products, the following formula was used: 
 Rn CFE C F T D= ⋅ ⋅ ⋅  (1) 
where CRn is the annual mean radon concentration; F is the equilibrium factor 
between radon and its decay products, for which the generally recommended value 
 Z.S. Zunic et al. 7 
 
S326 
(=0.4) was used; T is the time in hours spent by the pupils and teachers in the 
school under consideration (for pupils: T = (52 weeks y-1- 15 vacation weeks y-1) x 
25 h week-1 = 925 h y-1 and for teachers: T = (52 weeks y-1 - 6 vacation weeks y-1) x 
30 h week-1 = 1380 h y-1; and DCF is the dose conversion factor for radon decay 
products. Both the usual UNSCEAR DCF value and the recently updated ICRP one 
– 9 and 12 nSv (Bq h m-3)-1, respectively – were considered [13, 14]. The results of 
annual effective dose for pupils and teachers in all communities by using the 
UNSCEAR and ICRP DCF are summarized in Table 3. 
Table 3 
Descriptive statistics of annual effective dose E expected to be received by pupils and teachers  
in the Serbian schools using UNSCEAR and ICRP dose conversion factors 
 E (mSv y-1) 
  Min. Med. Max. AM SD GM GSD* 
pupils 0.06 0.32 1.42 0.39 0.26 0.32 1.9 UNSCEAR 
teachers 0.08 0.47 2.12 0.59 0.39 0.48 1.9 
pupils 0.08 0.42 1.90 0.53 0.34 0.43 1.9 ICRP 
 teachers 0.11 0.63 2.83 0.78 0.51 0.64 1.9 
Min.=Minimum; Med.=Median; Max.=Maximum; AM= Arithmetic Mean; SD=Standard Deviation; 
GM=Geometric Mean; GSD= Geometric Standard Deviation 
*GSD is dimensionless 
 
The estimated annual effective dose for pupils and teachers are higher than in 
a similar study in the Patras area of Greece where the annual effective doses were 
0.1 mSv and 0.2 mSv for pupils and teachers respectively [15]. 
Assuming that the long-term radon concentration is equal to the radon 
concentration present during the working hours and that the annual average 
occupancy is 1000 h per year, the results of an annual average effective dose to an 
Irish child from exposure to radon is 0.3 mSv [8]. 
4. CONCLUSIONS 
The results presented in this paper allow evaluation of exposure of pupils and 
teachers to radon and will serve as starting point for comparing radon concentration 
in primary schools and in dwellings, which will require further studies on the basis 
of both classical statistical and geostatistical methods. This survey was conducted 
by an international collaboration which was very effective in both designing and 
implementing the survey in Serbian primary schools. Due to fruitful collaboration 
at regional and local levels, the fraction of missing data in this survey is extremely 
low (less than 1 %). These results will contribute to the Serbian dataset for the 
European Atlas of Natural Radiation. 
8 Some results of a radon survey in 207 Serbian schools 
 
S327 
Acknowledgements. The support given by Ministry for Education and Science of the Republic 
of Serbia (P 41028) and authorities regarding schools and communities is highly appreciated.  
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Some results of a radon survey in 207 Serbian schools

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Some results of a radon survey in 207 Serbian schools

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