Open AccessArticle

The Radon Exhalation Rate and Dose Assessment of Granite Used as a Building Material in Serbia

Fathya Shabek

¹,

Božidar Obradović

²,

Igor Čeliković

^3,*

Mirjana Đurašević

Aleksandra Samolov

Predrag Kolarž

⁴ and

Aco Janićijević

Faculty of Technology and Metallurgy, University of Belgrade Karnegijeva 4, 11120 Belgrade, Serbia

School of Electrical Engineering, University of Belgrade, Bulevar kralja Aleksandra 73, 11120 Belgrade, Serbia

“Vinča” Institute of Nuclear Sciences, University of Belgrade, Mike Petrovica Alasa 12–14, 11351 Belgrade, Serbia

⁴

The Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia

Author to whom correspondence should be addressed.

Atmosphere 2024, 15(12), 1495; https://doi.org/10.3390/atmos15121495

Submission received: 8 November 2024 / Revised: 8 December 2024 / Accepted: 10 December 2024 / Published: 15 December 2024

(This article belongs to the Special Issue Atmospheric Radon Concentration Monitoring and Measurements (2nd Edition))

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Abstract

The application of energy-saving policies in buildings could lead to a decrease in the air exchange rate in dwellings, which could consequently lead to an increase in indoor radon concentration and, therefore, to an increase in resident exposure to ionizing radiation. The aim of the research presented in this paper is to investigate radiological exposure to residents due to the usage of different granites commonly used in Serbia as a building material. From the total of 10 analysed granite samples, a wide range of radon and thoron exhalation rates were found: from <161 μBq m⁻² s⁻¹ to 5220 ± 200 μBq m⁻² s⁻¹ and from <7 mBq m⁻² s⁻¹ to 5140 ± 320 mBq m⁻² s⁻¹, respectively. Assuming a low air exchange rate of 0.2 h⁻¹, the contribution of the measured granite material to the indoor radon concentration could go up to 150 Bq m⁻³. The estimated annual effective doses due to exposure to radon and thoron exhalation from the granite samples were (0.05–3.79) mSv and (<0.01–1.74) mSv, respectively. The specific activity of radionuclides ranged from 6.6 ± 0.5 Bq kg⁻¹ to 131.8 ± 9.4 Bq kg⁻¹ for ²²⁶Ra, from 0.5 ± 0.1 Bq kg⁻¹ to 120.8 ± 6.5 Bq kg⁻¹ for ²³²Th, and from 0.22 ± 0.01 Bq kg⁻¹ to 1321 ± 86 Bq kg⁻¹ for ⁴⁰K. The obtained external hazard index ranged from 0.03 to 1.48, with three samples above or very close to the accepted safety limit of 1. In particular, dwellings with a low air exchange rate (causing elevated radon) could lead to an elevated risk of radiation exposure.

Keywords:

radon exhalation rate; thoron exhalation rate; granite; building material; specific activity; doses; radiation hazard indices

1. Introduction

The World Health Organization has identified the radioactive noble gas radon and its progeny in the indoor environment as the second most common cause of lung cancers [1], being responsible for about 9% of all deaths due to lung cancer in Europe [2]. As a consequence, the European Commission—within the Basic Safety Standards Directive 2013/59/Euroatom—has obliged European Union member states to prepare radon action plans and to inform the public about their indoor radon values [3]. As a consequence, numerous national indoor radon surveys have taken place for the first time or have been repeated [4].

For the lower levels of a dwelling, like the basement, ground floor, and eventually the first floor, the major source of indoor radon is soil beneath the building, followed by building materials. At the higher levels, building materials become the most important source of radon. The major factor influencing the dilution of the indoor radon concentration is the air exchange rate with outdoor radon.

The main objective of the Paris Agreement is to limit global temperature increase to well below 2 °C above the pre-industrial level [5]. In order to achieve this, emissions of greenhouse gasses should be reduced. When home energy efficiency measures are correctly applied, they can provide warmer homes and reduced exposure to indoor air pollutants [6]. However, energy-efficient retrofit measures, like improving the sealing of window frames, changing all windows to double-glazed windows, and applying loft and wall insulation, will lead to increased indoor radon concentrations and other indoor pollutants [7,8]. It has been shown in many studies that a decrease in ventilation rates leads to an increase in indoor radon concentration [9,10,11,12].

Natural building materials and those containing waste products (fly ash from coal, alum shale, phosphogypsum) can considerably contribute to population exposure to natural radioactivity. The European Commission, within the Basic Safety Standard [3], has provided recommendations to introduce the regulatory control and screening of building materials. A large database of 24,200 samples of building materials used in different countries of the European Union was collected, out of which around 2000 different samples are related to radon exhalation rate measurements [13]. Of special concern are igneous rocks, such as granites, which could have significant amounts of naturally occurring radionuclides [14]. Therefore, it is not surprising that numerous researchers worldwide have studied the exhalation of radon from granite [15,16,17,18,19,20,21,22,23,24]. There have been several radon exhalation rate measurements in Serbia [25,26,27,28,29,30], but only a few regarding granite [26,27].

The aims of this paper are as follows:

To estimate internal exposure to ²²²Rn radon and ²²⁰Rn thoron exhaling from the selected granite samples commonly used in Serbia, especially in the context of the reduced air exchange rate in homes that have undergone energy-efficient retrofits;
To estimate effective doses due to exposure to radionuclides from selected granite samples.

2. Materials and Methods

2.1. Radon and Thoron Exhalation Rate

In total, 10 different specimens of granites were collected from several warehouses of building materials. All specimens were rectangular cuboids with a thickness much smaller than their length and width. The exhalation area of the samples ranged from 0.03 m² to 0.103 m², while the thickness of the sample was 0.02 m. The granite samples were placed vertically on their shortest side, with their large surfaces standing free in the air, thus not hindering the release of radon (Figure 1).

Radon exhalation rate measurements were performed using the well-known closed-chamber method [31,32,33]. Specimens were placed in a 30 dm³ accumulation chamber. The chamber was carefully sealed to prevent any radon leakage. The build-up of radon concentration in the chamber was continuously measured hourly over a period ranging from 5 days to 2 weeks, using the RTM 1688-2 active device from SARAD GmbH. Radon and thoron measurements were conducted with the RTM1688-2 device, which features a Si detector and a high-voltage chamber. The integration interval was set to 60 min. With the detector sensitivity of 4 cts (min kBqm⁻³)⁻¹ and an assumed measured concentration of 100 Bq/m⁻³, the measurement uncertainty was calculated to be 20%. The detection limit with a 95% confidence interval for the same integration period and detector sensitivity was 12.5 Bq/m³, as defined by producer specifications [34]. The radon surface exhalation rate, E_S (Bq m⁻² s⁻¹), can be determined by fitting the measured radon concentration C(t) (Bq m⁻³) using the following equation [31,32]:

C (t) = \frac{E_{S} S}{V λ_{e f f}} (1 - e^{- λ_{e f f} t}) + C_{0} e^{- λ_{e f f} t}

(1)

where S (m²) is the area of the sample, V (m³) is the air volume of the measurement system, λ_eff (s⁻¹) is the effective radon decay constant, and C₀ (Bq m⁻³) is the initial radon concentration in the chamber. The parameters E_S, C₀, and λ_eff are free parameters of the fit and are determined from the fitting process.

The effective radon decay constant represents the probability of radon removal from the chamber’s volume. It includes the natural decay of radon, radon leakage from the chamber, and back-diffusion, i.e., diffusion of radon from the air volume of the chamber back into the sample. When the sample volume is approximately 10% of the chamber volume, back-diffusion can be neglected [33]. In the case of the granite samples analysed in this research, the back-diffusion is negligible due to the small sample volume compared to the chamber volume.

Tracking temporal variations in radon concentrations introduces a certain time delay of 0.5–3 h. A method has recently been developed that improves the time resolution of radon measurements using an airflow-through method with scintillation cells [35]. For cases when radon exhalation is estimated from only a few hours of measurements, this time delay should be addressed appropriately. However, the duration of measurements conducted in this research was at least 5 days, and the time delay could be neglected.

In cases of a low radon exhalation rate, the build-up of radon concentration in the chamber may not be observed (i.e., it is within the measurement uncertainty). In such cases, only an upper limit can be determined. To estimate the upper limit, Equation (1) is used, where C(t) corresponds to the radon concentration taken from the last measurement point, while t is the measurement duration (i.e., time elapsed between the first and the last measurement). The second term of Equation (1) is neglected.

Thoron (²²⁰Rn) exhalation rate measurements, due to its shorter half-life (τ_1/2 = 55.6 s) compared to radon (²²²Rn) (τ_1/2 = 3.82 days), were performed in a smaller chamber of 2.8 dm³ volume for several hours to a few days with an integration time of 1 h. Due to a short half-life, the initial thoron concentration can be neglected, as well as the exponential component of Equation (1); thus, the exhalation rate can be extracted from the constant part of Equation (1). Since a secular equilibrium between ²²⁴Ra and thoron is achieved within a few minutes, the saturation of the thoron concentration occurs very quickly. Consequently, the build-up of the thoron concentration could be seen only for the sampling time of a few minutes. The measured thoron concentration was therefore averaged over the entire measuring period.

2.2. Gamma Spectrometry

After performing radon and thoron exhalation rate measurements, a small part of each specimen was prepared for gamma spectrometric analysis. Samples were crushed, sieved through a 2 mm mesh, and placed in 125 mL cylindrical containers. The containers were sealed and left for at least 40 days before measurements in order to reach secular equilibrium between ²²⁶Ra and ²²²Rn.

Measurements were performed with two HPGe detectors: AMETEK-ORTEC GEM 30–70, Oak Ridge, USA, with a relative efficiency of 37% and Canberra GX5019, Mirion Technoloies, Olen, Belgium, with 55% relative efficiency. The resolution at the 1332.5 keV transition of ⁶⁰Co was 1.7 keV and 1.9 keV, respectively. The measurement duration ranged from 250,000 s to 330,000 s.

Efficiency was obtained from the working standard that was prepared in the “Vinča“ Institute of Nuclear Sciences [36] in the same geometry as the samples, containing a matrix of crushed and sieved building material spiked with a certified standard solution from the Czech Metrology Institute. This solution included radionuclides ²⁴¹Am, ¹⁰⁹Cd, ¹³⁹Ce, ⁵⁷Co, ⁶⁰Co, ¹³⁷Cs, ¹³³Ba, ⁸⁵Sr, ⁸⁸Y, ⁵¹Cr, and ²¹⁰Pb [37]. The uncertainty in the mixture of radionuclides ranged from 0.5% to 1.7%, depending on the radionuclides, while the uncertainty in the prepared standard was less than 3% [36].

Spectra were analysed using Genie2000 Software [38]. In this paper, only the specific activities of ²²⁶Ra, ²³²Th, and ⁴⁰K radionuclides relevant to estimating radiological hazard indices are presented. The specific activity of ²²⁶Ra was obtained via the most intense transitions of its decay products ²¹⁴Pb (295.224 keV and 351.932 keV) and ²¹⁴Bi (609.316 keV, 1120.295 keV, and 1764.498 keV). The specific activity of ²³²Th was obtained from the net peak areas of 338.319 keV, 911.209 keV and 968.968 keV transitions of ²²⁸Ac. The specific activity of ⁴⁰K was obtained from the intensity of the 1460.822 keV transition, corrected for the contribution from the 1459.131 keV transition of ²²⁸Ac, which cannot be resolved.

2.3. Dose Assessment and Radiation Hazard Indices

To assess internal exposure to radon and thoron, as well as external exposure to gamma radiation originating from granite, a standard room model with dimensions 5 × 4 × 2.8 m³ was used.

The indoor radon concentration resulting from the use of granite as an interior building material, assuming that it completely covers walls, can be expressed as:

C_{R n} = \frac{E_{S R n} S}{λ_{V} V}

(2)

where E_SRn (μBq m⁻² s⁻¹) is the radon exhalation rate from the wall area S (m²) (please note that S is different than S used in formula 1), V (m³) is the volume of the room, and λ_V (h⁻¹) is the ventilation rate or the air exchange rate.

The annual effective doses E (mSv y⁻¹) due to the inhalation of radon can be calculated as [39]:

E_{R n} = C_{R n} F_{R n} D C F_{R n} O

(3)

where C_Rn (Bq m⁻³) is the indoor radon concentration originating from exhalation from building material (granite); F_Rn is the radon equilibrium factor of 0.4 [39], DCF_Rn is the Rn dose conversion factor of 9 nSv (Bqhm⁻³)⁻¹ recommended by UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation) [39], and O is the annual occupancy of 7000 h.

Due to the short half-life of thoron and its limited diffusion length, the spatial distribution of thoron within a room is nonuniform and cannot be given with a single value, and thus, it is suggested that the thoron concentration should not be used for the dose assessment [40]. However, it has been shown that assuming the typical room parameters given in [41,42,43], the equilibrium equivalent thoron concentration EETC (Bq m⁻³) in the room can be expressed as [40]:

E E T C = 3.36 E_{S T n} \cdot S / V

(4)

where E_STn is the thoron exhalation rate (Bq m⁻² s⁻¹) and S/V is the surface-to-volume ratio, which can vary based on the shape of the room, with a standard value of 0.36 m⁻¹.

It is suggested that the thoron exhalation rate could be used for a dose assessment, which is the approach followed in this paper [40]. The doses from thoron were estimated as:

E_{T n} = E E T C \cdot D C F_{T n} \cdot O

(5)

where DCF_Tn is the thoron dose conversion factor of 40 nSv (Bqhm⁻³)⁻¹, as recommended by UNSCEAR [39].

The exposure to external radiation can be assessed by calculating the absorbed gamma dose rate

\dot{D}

(nGy h⁻¹) and the annual effective dose D_E (mSv) [39]:

\dot{D} = 0.92 C_{R a} + 1.1 C_{T h} + 0.08 C_{K}

(6)

D_{E} = 0.7 \cdot 7000 \dot{D}

(7)

Additional indices used to assess radiation hazard include the radium equivalent Ra_eq and external hazard index H_ex [39,44]:

R a_{e q} = C_{R a} + 1.43 C_{T h} + 0.077 C_{K}

(8)

H_{e x} = \frac{C_{R a}}{370} + \frac{C_{T h}}{259} + \frac{C_{K}}{4810}

(9)

3. Results and Discussion

3.1. Radon and Thoron Exhalation Rates

As an example of the closed chamber method [30,31], a build-up of radon in the accumulation box due to its exhalation from Sample 1 is shown in Figure 2.

The measured radon concentrations over time were fitted using Equation (1). From the fit, a surface exhalation rate E_S of 5220 ± 200 μBq m⁻² s⁻¹, an effective decay constant λ_eff of 2.45 ± 0.25 μs, and an initial radon concentration C₀ of 32 ± 23 Bq m⁻³ were deduced. The difference between the effective decay constant and the radon decay constant (λ_Rn = 2.1 · 10⁻⁶s⁻¹) is 0.35 · 10⁻⁶ s⁻¹, which corresponds to the radon leakage from the accumulation chamber. However, with continuous radon measurements, leakage does not represent a problem, as the radon exhalation rate is deduced directly by fitting the experimental results.

The thoron exhalation rate was also deduced from Equation (1), where the exponential part can be neglected since equilibrium is reached within several minutes. Thoron concentration is obtained by averaging the concentration measured inside the accumulation chamber. The results of the radon and thoron surface exhalation rates for 10 selected granite samples are presented in Table 1 and are shown graphically in Figure 3.

For different granite samples, a wide range of radon and thoron surface exhalation rates was observed, varying from <161 μBq m⁻² s⁻¹ to 5220 ± 200 μBq m⁻² s⁻¹ and from <7 mBq m⁻² s⁻¹ to 5140 ± 320 mBq m⁻² s⁻¹, respectively.

The obtained results of the radon and thoron surface exhalation rates from the granite samples, along with similar measurements performed worldwide, are shown in Table 2.

The obtained data align with previously published and estimated radon and thoron exhalation rates from granites analysed in Serbia [26,27] and worldwide [14,15,16,17,18,19,20,21,22,23,24].

While there are numerous measurements of radon exhalation rates, data on thoron exhalation rates from building materials remain scarce. The first intercomparison of the thoron exhalation rate measurements performed recently has shown that a harmonized standard of thoron exhalation rate measurements should be developed [45].

3.2. Gamma Spectrometry

In Table 1, specific activities of ²²⁶Ra, ²³²Th, and ⁴⁰K from the granite samples are presented as well. A wide range of specific activities of ²²⁶Ra, ²³²Th, and ⁴⁰K were also found. The specific activity of ²²⁶Ra ranges from 6.6 ± 0.5 Bq kg⁻¹ to 131.8 ± 9.4 Bq kg⁻¹, of ²³²Th ranges from 0.5 ± 0.1 Bq kg⁻¹ to 120.8 ± 6.5 Bq kg⁻¹, and of ⁴⁰K ranges from 0.22 ± 0.01 Bq kg⁻¹ to 1321 ± 86 Bq kg⁻¹. The ²²⁶Ra, ²³²Th, and ⁴⁰K specific activities of the analysed samples are graphically shown in Figure 4. These results are consistent with the analysis of granite samples conducted globally, as shown in Table 2, and with the additional literature not included in Table 2 [46,47,48,49,50].

A correlation factor between the radon surface exhalation rate and ²²⁶Ra specific activity in granite was found to be 0.83, while a very weak correlation of 0.30 was found between the thoron surface exhalation rate and the specific activity of ²³²Th. This behaviour is expected. In dense materials such as granites, the radon diffusion length is in the range of 0.1–0.15 m [51], which is 5–10 times larger than the thickness of the samples, allowing radon to diffuse out of the material. On the other hand, the diffusion length of thoron is almost two orders of magnitude smaller than the diffusion length of radon; thus, only a small fraction of thoron will diffuse out of the sample. Therefore, since thoron exhalation strongly depends on granite characteristics such as grain size, pore size distribution, etc., it is not surprising for the correlation between ²²⁰Rn and ²³²Th to be weak.

The indoor radon concentration originating only from the radon exhalation from the granite was extracted based on Equation (2). According to UNSCEAR, the air exchange rate ranges from 0.2 h⁻² to 2 h⁻¹, with a geometrical mean of 0.63 h⁻¹ [21]. Furthermore, many experimental results have confirmed an increase in indoor radon concentrations after house retrofitting [6,7,8,9,10,11,12]. For instance, in the UK, it was demonstrated that window replacement could reduce the air exchange rate by 0.23 h⁻¹; in percentages, this would correspond to around a 35% air exchange rate reduction [9]. Table 3 represents indoor radon concentrations due to granite exposure, assuming an average air exchange rate of 0.63 h⁻¹, a small air exchange rate of 0.2 h⁻¹, and a further reduction to 35% due to house retrofitting.

The air exchange rate does not significantly affect the indoor thoron concentration because of its much shorter lifetime compared to the air exchange rate. Additionally, because of a small diffusion length, its concentration is not uniform within the room, and a better approach would be to estimate the equilibrium equivalent thoron concentration as described in Equation (3). The calculated EETC values are also presented in Table 3.

3.3. Dose Assessment and Radiation Hazard Indices

From the estimated indoor radon and thoron concentration based on radon and thoron exhalation from the granite walls and the measured specific activities of ²²⁶Ra, ²³²Th, and ⁴⁰K, the annual effective doses due to the inhalation of radon (assuming λ_v = 0.2 h⁻¹) and EETC (Equations (3) and (5)), and the annual effective dose, the radium equivalent concentration and external hazard index due to exposure to external radiation were assessed and presented in Table 4. A graphical representation of the received doses is given in Figure 5, and the external hazard index H_ex is shown in Figure 6.

Although national authorities do not regulate limits due to the exposure to indoor thoron concentrations, it is shown that annual effective doses due to the exposure to the inhalation of thoron exhaling from a few granite samples are close to 1 mSv (i.e., 1.74 mSv and 0.84 mSv). This indicates that the received doses are not negligible, underscoring the importance of measuring thoron exhalation rates from building materials.

As previously mentioned, the estimation of the annual effective dose due to internal exposure to indoor radon and thoron concentrations, a DCF of 9 nSv (Bq h m⁻³)⁻¹ for radon and 40 nSv (Bq h m⁻³)⁻¹ for thoron were used as proposed by UNSCEAR. The International Commission on Radiological Protection (ICRP) afterwards proposed a DCF of 16.8 nSv (Bq h m⁻³)⁻¹ for radon and 107 nSv (Bq h m⁻³)⁻¹ for thoron [52]. Although the UNSCEAR recently confirmed their previous dose conversion factors [53], it is worth mentioning that when using the ICRP’s DCF values, doses due to exposure to radon and thoron would be 1.9 and 2.7 times higher than the doses reported in Table 4, thus ranging from (0.22 to 7.1) mSv y⁻¹ for radon and (<0.03 to 4.7) mSv y⁻¹.

4. Conclusions

In this paper, the radon and thoron exhalation rates, along with specific activities of ²²⁶Ra, ²³²Th, and ⁴⁰K, in 10 different granite samples were measured in order to assess their radiological impact on residents. Particular attention was given to dwellings with low air exchange rates, especially considering that thermally retrofitted dwellings may experience further additional reductions in the air exchange rate.

A wide range of radon and thoron exhalation rates is found from <161 μBq m⁻² s⁻¹ to 5220 ± 200 μBq m⁻² s⁻¹ and from <7 mBq m⁻² s⁻¹ to 5140 ± 320 mBq m⁻² s⁻¹, respectively. The deduced radon doses, assuming a low air exchange rate of 0.2 h⁻¹, range from (0.05 to 3.79) mSv h⁻¹, while the estimated thoron doses range from (<0.01 to 1.74) m Sv y⁻¹. Among the analysed samples, two had annual effective doses due to the inhalation of radon and thoron above 1 mSv, and one sample was above 3 mSv. Since these doses are only from the building material, radon and thoron exposure could be a health hazard issue even on the higher floors that utilize such materials; therefore, the exhalation rates of building materials should be measured.

The specific activity of ²²⁶Ra ranged from (6.6 ± 0.5 to 131.8 ± 9.4) Bq kg⁻¹, of ²³²Th ranged from (0.5 ± 0.1 to 120.8 ± 6.5) Bq kg⁻¹, and from (0.22 ± 0.01 to 1321 ± 86) Bq kg⁻¹ for ⁴⁰K. The obtained external hazard index ranged from 0.03 to 1.48, with three samples above or very close to the accepted safety limit of 1. Especially for dwellings with low air exchange rates (causing elevated radon), this could lead to an elevated risk of radiation exposure.

Author Contributions

Conceptualization, I.Č.; methodology, I.Č. and M.Đ.; validation, P.K.; formal analysis, F.S., B.O., I.Č. and M.Đ.; investigation, F.S., B.O., M.Đ. and A.S.; writing—original draft, I.Č.; writing—review and editing, F.S., B.O., I.Č., M.Đ., A.S., P.K. and A.J.; supervision, I.Č. and A.J. All authors have read and agreed to the published version of this manuscript.

Funding

This work was financially supported by the Ministry of Science, Technological Development, and Innovation of the Republic of Serbia through Contract No. 451-03-47/2023-01/200017, and Contract No. 451-03-47/2023-01/200135. This work was also supported by the Science Fund of the Republic of Serbia, the Green program of cooperation between science and industry, grant no. 5661. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funder.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data and materials are available on request from the corresponding author. The data are not publicly available due to ongoing research using a part of the data.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Schematic drawing of radon exhalation rate measurement.

Figure 2. The build-up of radon exhaling from Sample 1 in a 30 L accumulation chamber. Experimental data are fitted on a theoretical curve given by Equation (1). From the fit, values of E_S, C₀, and λ_eff are extracted.

Figure 3. Radon and thoron surface exhalation rates from 10 different granite samples obtained using the closed-chamber accumulation method.

Figure 4. Specific activities of ²²⁶Ra, ²³²Tn, and ⁴⁰K of 10 selected granite samples.

Figure 5. The annual effective doses due to the inhalation of radon (λ_v = 0.2 h⁻¹) and thoron (EECT), as well as due to the exposure to external radiation.

Figure 6. External hazard index.

Table 1. Results of the radon and thoron surface exhalation rates as well as the specific activity of ²²⁶Ra, ²³²Th, and ⁴⁰K of 10 analysed granite samples.

Sample ID	E_Rn (μBq m⁻² s⁻¹)	E_Tn (mBq m⁻² s⁻¹)	²²⁶Ra (Bq kg⁻¹)	²³²Th (Bq kg⁻¹)	⁴⁰K (Bq kg⁻¹)
1	5220 ± 200	5140 ± 320	131.8 ± 9.4	120.8 ± 6.5	1288 ± 84
2	622 ± 21	112 ± 56	84.5 ± 6.1	39.2 ± 2.3	885 ± 64
3	670 ± 36	616 ± 35	37.9 ± 2.8	285 ± 15	1321 ± 86
4	<170	678 ± 81	30.9 ± 2.3	52.9 ± 2.9	1093 ± 72
5	1646 ± 49	2470 ± 150	93.5 ± 6.8	109.2 ± 5.6	1234 ± 63
6	<185	514 ± 72	29.0 ± 2.2	39.2 ± 2.3	1108 ± 57
7	64 ± 14	<7	57.3 ± 4.1	63.8 ± 3.5	691 ± 36
8	<161	<21	6.6 ± 0.5	2.3 ± 0.3	59.9 ± 3.2
9	257 ± 24	<18	11.8 ± 0.9	0.5 ± 0.1	0.22 ± 0.01
10	243 ± 24	1240 ± 100	35.7 ± 2.6	53.3 ± 2.8	1223 ± 62

Table 2. Radon and thoron exhalation rate measurements and activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K reported worldwide.

E_Rn (μBq m⁻² s⁻¹)	E_Tn (mBq m⁻² s⁻¹)	²²⁶Ra (Bq kg⁻¹)	²³²Th (Bq kg⁻¹)	⁴⁰K (Bq kg⁻¹)	References
240–10,300	81–6290	97–294	183–470	85–264	[14]
41–471					[15]
10–38		30–122	12–62	127–1335	[16]
62–790	7.5–425	51–239	10–124		[17]
3000–37,000	40–3330				[18]
67–1090		12–252	9.55–347.5	407.5–1615	[19]
0.14–2650					[20]
max: 258					[21]
361–389		10–187	16–354	104–1630	[22]
average: 138					[23]
389–2175					[24]
33.6-	42.3				[26]
861–1039		23–280	77–426	550–2240	[27]
161–5220	<7–5140	6.6–131.8	0.5–120.8	0.22–1321	This study

Table 3. Contribution to the indoor radon concentration from granite, assuming a 0.63 h⁻¹, 0.2 h⁻¹, and 0.13 h⁻¹ air exchange rate and equilibrium equivalent thoron concentration.

Sample ID	C_Rn (Bq m⁻³) λv = 0.63 h⁻¹	C_Rn (Bq m⁻³) λv = 0.2 h⁻¹	C_Rn (Bq m⁻³) λv = 0.13 h⁻¹	EETC (Bq m⁻³)
1	47.7 ± 1.8	150.3 ± 5.8	231.3 ± 8.9	6.22 ± 0.39
2	5.7 ± 0.2	17.9 ± 0.6	27.6 ± 0.9	0.14 ± 0.07
3	6.1 ± 0.3	19.3 ± 1.0	29.7 ± 1.6	0.75 ± 0.04
4	<1.5	<4.9	<7.5	0.82 ± 0.10
5	15.0 ± 0.4	47.4 ± 1.4	72.9 ± 2.2	2.99 ± 0.18
6	<1.7	<5.3	<8.2	0.62 ± 0.09
7	0.6 ± 0.1	1.8 ± 0.4	2.8 ± 0.6	-
8	<1.5	<4.6	<7.1	0.03
9	2.3 ± 0.2	7.4 ± 0.7	11.4 ± 1.1	0.02
10	2.2 ± 0.2	7.0 ± 0.7	10.8 ± 1.1	1.50 ± 0.12

Table 4. The annual effective doses due to the inhalation of radon (λ_v = 0.2 h⁻¹) and thoron (EECT), as well as the annual effective dose, radium equivalent concentration, and external hazard index due to exposure to external radiation.

Sample ID	D_ERn (mSv)	D_ETn (mSv)	D_E (mSv)	Ra_eq	H_ex
1	3.79	1.74	1.75	402.92	1.09
2	0.45	0.04	0.94	208.70	0.56
3	0.49	0.21	2.22	547.17	1.48
4	0.12	0.23	0.85	190.71	0.51
5	1.19	0.84	1.49	344.67	0.93
6	0.13	0.17	0.78	170.37	0.46
7	0.05	0.00	0.87	201.74	0.54
8	0.12	0.01	0.07	14.50	0.04
9	0.19	0.01	0.06	12.53	0.03
10	0.18	0.42	0.93	206.09	0.56

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Shabek, F.; Obradović, B.; Čeliković, I.; Đurašević, M.; Samolov, A.; Kolarž, P.; Janićijević, A. The Radon Exhalation Rate and Dose Assessment of Granite Used as a Building Material in Serbia. Atmosphere 2024, 15, 1495. https://doi.org/10.3390/atmos15121495

AMA Style

Shabek F, Obradović B, Čeliković I, Đurašević M, Samolov A, Kolarž P, Janićijević A. The Radon Exhalation Rate and Dose Assessment of Granite Used as a Building Material in Serbia. Atmosphere. 2024; 15(12):1495. https://doi.org/10.3390/atmos15121495

Chicago/Turabian Style

Shabek, Fathya, Božidar Obradović, Igor Čeliković, Mirjana Đurašević, Aleksandra Samolov, Predrag Kolarž, and Aco Janićijević. 2024. "The Radon Exhalation Rate and Dose Assessment of Granite Used as a Building Material in Serbia" Atmosphere 15, no. 12: 1495. https://doi.org/10.3390/atmos15121495

APA Style

Shabek, F., Obradović, B., Čeliković, I., Đurašević, M., Samolov, A., Kolarž, P., & Janićijević, A. (2024). The Radon Exhalation Rate and Dose Assessment of Granite Used as a Building Material in Serbia. Atmosphere, 15(12), 1495. https://doi.org/10.3390/atmos15121495

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