## 4 Results and Discussion
### Potential Health Hazards Assessment
#### 4.3.6 Indoor Radon Exhalation and Concentration  
As a result of radium (\({}^{226}\)Ra) disintegration of soils, rocks, and their products (construction materials), radon (\({}^{222}\)Rn) is generated and flows through their pores into the air [31]. The biggest annual radiation dose incurred by people arises from radon and its offspring in the air. Lung cancer probability can largely increase as a result of incurring this dose for the long term, especially in dwellings. Hence, it is important to estimate the activity concentration and the exhalation rate of indoor radon.  
Evaluation of radon exhalation rate (RER), in building materials, and determining the resulting indoor radon concentration [70] is vital. As per the European Commission European Commission [20] for a model of a standard room of dimensions 4 m \(\times\) 5 m \(\times\) 2.8 m tiled with granitic slabs of 3 cm thickness (2600 kg/m\({}^{3}\) density) in its walls and floor, and depending on the \({}^{226}\)Ra concentration (AC\({}_{\text{Ra}}\)), the following equation gives theoretically radon exhalation rate RER in Bq m\({}^{-2}\) h\({}^{-1}\) as described [28; 71]:  
\[\text{RER}=(\text{AC}_{Ra}\cdot\lambda\cdot\rho\cdot\eta\cdot d)/2 \tag{9}\]  
where \(\lambda\) (=0.0076/ h) is the \({}^{226}\)Ra decay constant and \(\rho\) (=2600 kg/m\({}^{3}\)), \(\eta\) (=0.45) and \(d\) (=0.03 m) are the density, emanation coefficient, and thickness of granite slab used in tiling the room, respectively [28].  
Table 4 shows the mean value (5.17 \(\pm\) 0.45 Bq m\({}^{-2}\) h\({}^{-1}\)) and range (2.25 to 9.6 Bq m\({}^{-2}\) h\({}^{-1}\)) of RER from ElSibai-Abu ElTiyur granites. They are consistent with previous studies ([PERSON] et al. [72]) on building materials falling within the range 0.013 to 13 Bq m\({}^{-2}\) h\({}^{-1}\), and within the range (0.01 to 21 Bq m\({}^{-2}\) h\({}^{-1}\)) published by other authors [32; 63; 72] using different analytical methods.  
According to the theoretical evaluation of radon exhalation rate in Equation (9), the indoor radon concentration (IRC) in Bq/m\({}^{3}\) was calculated as follows [28; 63]:  
\[\text{IRC}=\frac{RER\cdot S}{(\lambda+\lambda_{o})\cdot V} \tag{10}\]  
where \(S\) (in m\({}^{2}\)), \(V\) (in m\({}^{3}\)), and \(\lambda_{o}\) (in h\({}^{-1}\)) are the surface area exhaled radon, room air volume, rate of air removal by ventilation, respectively. In this work, the worst cases were considered, where the removal rate by poor ventilation (\(\lambda_{o}\) = 0.1 h\({}^{-1}\)) and emanation coefficient value (\(\eta\) = 0.45) were taken [28; 63; 73]. Moreover, furniture occupancy has been  
Figure 11: Variation of ELCR in the investigated samples.  
taken into consideration, consequently, the value of 2 m\({}^{-1}\) for the proportion S/V in the above equation has been taken [28].  
The computed radon exhalation rate values (RER) for the investigated gramitic samples of ElSibai-Um EITiyur (Table 4 and Figure 12) varied between 2.25 to 9.60 Bq m\({}^{-2}\) h\({}^{-1}\) with an average of 5.17 \(\pm\) 0.45 Bq m\({}^{-2}\) h\({}^{-1}\). According to the RER values, the indoor radon concentration (IRC) was calculated. The IRC values range from 41.88-178.50 Bq m\({}^{-3}\) with an average of 96.01 \(\pm\) 8.38 Bq m\({}^{-3}\) (Table 4 and Figure 12). This average is above the world average (40 Bq m\({}^{-3}\)) (UNSCEAR [21], but still below the permissible range (100 to 300 Bq m\({}^{-3}\)) as recommended by the World Health Organization (WHO) [60] (Figure 12). This is quite clear, where 60% of the samples fulfills IRC \(<\) 100 Bq m\({}^{-3}\) formula, while the remaining 40%, 100 \(<\) IRC \(<\) 300 Bq m\({}^{-3}\) (Table 4). This mean value of indoor radon concentrations (IRC) is below the recommended limit of 200 Bq m\({}^{-3}\) (European Commission European Commission [20] and ICRP [61]. Accordingly, the population exposure is unaffected significantly by radon emission from ElSibai-Abu EITiyur granites if they are employed as tiles in residences.