The literature proves an evident association between indoor radon exposure and lung cancer, even at low doses. This study brings a new approach to the study of children’s exposure to radon by aiming to evaluate exposure to indoor radon concentrations in nursery and primary schools from two districts in Portugal (Porto and Braganca), considering different influencing factors (occupation patterns, classroom floor level, year of the buildings’ construction and soil composition of the building site), as well as the comparison with IAQ standard values for health protection. Fifteen nursery and primary schools in the Porto and Braganca districts were considered: five nursery schools for infants and twelve for pre-schoolers (seven different buildings), as well as eight primary schools. Radon measurements were performed continuously. The measured concentrations depended on the building occupation, classroom floor level and year of the buildings’ construction. Although they were in general within the Portuguese legislation for IAQ, exceedances to international standards were found. These results point out the need of assessing indoor radon concentrations not only in primary schools, but also in nursery schools, never performed in Portugal before this study. It is important to extend the study to other microenvironments like homes, and in time to estimate the annual effective dose and to assess lifetime health risks.

https://www.mdpi.com/1660-4601/13/4/386/pdf

Children’s Exposure to Radon in Nursery and Primary Schools

Radiological characterization of building materials used in Malaysia and assessment of external and internal doses

Subject of this study is an investigation of the variations of indoor radon concentration and ambient dose equivalent rate in outdoor and indoor environments of 40 dwellings, 31 elementary schools and five kindergartens. The buildings are located in three municipalities of two, geologically different, areas of the Republic of Macedonia. Indoor radon concentrations were measured by nuclear track detectors, deployed in the most occupied room of the building, between June 2013 and May 2014. During the deploying campaign, indoor and outdoor ambient dose equivalent rates were measured simultaneously at the same location. It appeared that the measured values varied from 22 to 990 Bq/m3 for indoor radon concentrations, from 50 to 195 nSv/h for outdoor ambient dose equivalent rates, and from 38 to 184 nSv/h for indoor ambient dose equivalent rates. The geometric mean value of indoor to outdoor ambient dose equivalent rates was found to be 0.88, i.e. the outdoor ambient dose equivalent rates were on average higher than the indoor ambient dose equivalent rates. All measured can reasonably well be described by log-normal distributions. A detailed statistical analysis of factors which influence the measured quantities is reported.

Variation of indoor radon concentration and ambient dose equivalent rate in different outdoor and indoor environments

This paper presents the methodology and results of the national radon survey in Bulgaria and its spatial variability. The measurements were carried out in 2778 dwellings using CR-39 track detectors over two successive 9 and 3-month periods from April 2015 to March 2016. The arithmetic (AM) and geometric (GM) means of annual indoor radon concentration were 111 ± 105 Bq/m3 and 81 Bq/m3 (GSD = 2.15), respectively. The distribution of data has been accepted to be log-normal. Two hypotheses have been investigated in the paper. The first one was a spatial variation of indoor radon concentration and the second was spatiality of the factor that influences radon variation. The indoor radon concentrations in the 28 districts have been significantly different, which prove the first hypothesis. The influence of the factors, geology (geotectonic unit, type of rock, and faults distance of the measuring site), type of the region, and the presence of the basement in the building on radon spatial variation, was examined. The analyses have been shown that they significantly affect radon variations but with a relatively small contribution in comparison to the radon variation between district. Furthermore, the significance and contribution of the investigated factors were different in each district, which confirmed the second hypothesis for their spatiality.

Analysis of the spatial variation of indoor radon concentrations (national survey in Bulgaria).

The study was conducted to assess the spatiality of the building factors’ effect on air quality through evaluation of indoor radon concentration in areas with different geology and geographical position. For that matter, a survey of indoor radon concentration was carried out in 174 kindergartens of three Bulgarian cities. The time-integrated measurements were performed in 777 ground floor rooms using alpha tract detectors, exposed for 3 months in cold period of 2014. The results of indoor radon concentrations vary from 20 to 1117 Bq/m3. The differences in the mean radon concentrations measured in the different cities were related to geology. The effect of building-specific factors: elevator, basement, mechanical ventilation, type of windows, number of floors, building renovation, building materials, type of room, type of heating, construction period, and availability of foundation on radon concentration variations was examined applying univariate and multivariate analysis. Univariate analysis showed that the effects of building-specific factors on radon variation are different in different cities. The influence of building factors on radon concentration variations was more dominant in inland cities in comparison to the city situated on the sea coast. The multivariate analysis, which was applied to evaluate the impact of building factors simultaneously, confirmed this influence too.

Building-specific factors affecting indoor radon concentration variations in different regions in Bulgaria

As a part of the systematic survey of indoor radon in Bulgaria, indoor radon concentration
was measured in 292 kindergartens buildings of Sofia city during 3 month (January – April),
2013 using the CR-39 nuclear tracts detectors. In any building 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
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 radon concentration in Sofia dwellings obtained from
previous study. A detailed statistical analysis of the building factors was present.

Measurement of indoor radon concentration in kindergartens in Sofia, Bulgaria

We present a method for the estimation of annual radon concentration based on
 short-term (three months) measurements. The study involves results from two
 independent sets of indoor radon concentration measurements performed in 16
 cities of the Republic of Macedonia. The first data set contains winter and
 annual radon concentration obtained during the National survey in 2010 and
 the second, contains only the radon concentration measured during the winter
 of 2013. Both data sets pertain to radon concentration from the same cities
 and have been measured applying the same methodology in ground floor
 dwellings. The results appeared to be consistent and the dispersion of radon
 concentration was low. Linear regression analysis of the radon concentration
 measured in winter of 2010 and of the 2010 annual radon concentration
 revealed a high coefficient of determination R2 = 0.92, with a relative
 uncertainty of 3%. Furthermore, this model was used to estimate the annual
 radon concentration solely from winter-term measurements performed in
 2013. The geometrical mean of the estimated annual radon concentration of
 the 2013: radon concentration (A-2013) =98 Bqm-3 was almost equal to the
 geometrical mean of the annual radon concentration from the 2010, radon
 concentration (A-2010) = 99 Bqm-3. Analysis of the influence of building
 characteristics, such as presence/absence of a basement in the building, or
 the dominant building material on the estimated annual radon concentration
 is also reported. Our results show that a low number of relatively
 short-term radon measurements may produce a reasonable insight into a gross
 average obtained in a larger survey.

/pdf/prediction-of-long-term-indoor-radon-concentration-based-on-il7ux2huhr.pdf

Martina Tsenova

Papers

Measurement of indoor radon concentration in kindergartens in Sofia, Bulgaria

Variation of indoor radon concentration and ambient dose equivalent rate in different outdoor and indoor environments

Building-specific factors affecting indoor radon concentration variations in different regions in Bulgaria

Prediction of long-term indoor radon concentration based on short-term measurements