# Evaluation of the Radiological and Chemical Risk for Public Health from Flour Sample Investigation
## 2 Materials and Methods
### Gamma Spectrometry Analysis and Radiological Hazard Effects Assessment  
For the gamma spectrometry investigations, samples were packed in a 20 mL polyethylene plastic vial to reach a geometry homogeneity around the detector; then, the respective net weights were measured and recorded. After this preparation step, they were counted for 70,000 s, and spectra were analyzed in order to obtain the activity concentration of \({}^{137}\)Cs and \({}^{40}\)K, through the evaluation of their \(\gamma\)-lines at 661.66 keV and 1460.81 keV, respectively. A positively-biased Ortec HPGe detector (GEM) (FWHM of 1.85 keV; peak-to-Compton ratio of 64:1; relative efficiency of 40% at the 1.33 MeV \({}^{60}\)Co \(\gamma\)-line), placed inside lead wells to shield the background radiation environment, was employed for the analysis. A photo of the experimental setup is reported in Figure 2.  
A multipeak Marinelli geometry gamma source (AK-5901) of 1 L capacity, covering the energy range 59.54-1836 keV, customized to reproduce the exact geometries of samples in a water-equivalent epoxy resin matrix, was employed for efficiency and energy calibrations. The ANGLE 4 code was employed for the efficiency transfer factor calculations to the 20 mL vial sample holder geometry [33]. For data acquisition and analysis, Gamma Vision (Ortec) software was used [34].  
The activity concentration (C) of each detected radionuclide was calculated according to the following [35; 36]:  
\[C=\frac{N_{E}}{\epsilon_{E}t\gamma_{d}M} \tag{1}\]  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Sample ID** & **Sample Typology** \\ \hline S1 & Wholemeal flour \\ S2 & Semolina flour \\ S3 & Rice flour \\ S4 & Coconut flour \\ S5 & Almond flour \\ S6 & Chestnut flour \\ S7 & Mallorcan wheat flour \\ S8 & Oat flour \\ S9 & Corn flour \\ S10 & Rye flour \\ S11 & Pistachio flour \\ \hline \hline \end{tabular}
\end{table}
Table 1: List of investigated types of flour, together with their identification code (ID) and typology.  
Figure 2: HPGe gamma spectrometry setup.  
where \(N_{E}\) indicates the net area of the radioisotope photopeak; \(\varepsilon_{E}\) and \(\gamma_{d}\) are the efficiency and yield of the photopeak, respectively; \(M\) is the mass sample (g); and \(t\) is the lifetime (s).  
The resulting uncertainty of each measurement, with coverage factor \(k=2\), was calculated, taking into account the uncertainty of the counting estimation, of the calibration source, of the efficiency calibration, of the background subtraction, and of the \(\gamma\)-branching ratio [37].  
The quality of the gamma spectrometry experimental results was certified by the Italian Accreditation Body (ACCREDIA) [38].  
This implies the continued verification (with annual periodicity) of the maintenance of the gamma spectrometry method performance characteristics.  
The repeatability of the results, in particular, is verified over time with the double test method. A certified reference material (also containing the radionuclides \({}^{40}\)K and \({}^{137}\)Cs) is analyzed twice, with the active concentration of the radionuclide of interest defined as \(x_{1}\) (first measurement) and \(x_{2}\) (second measurement). The probability level \(p=0.95\) is considered. The following formula is applied:  
\[|x_{1}-x_{2}|\leq\sqrt{2}\cdot s_{r}\cdot t\]  
where \(t\) is the Student variable, and \(s_{r}\) is the standard deviation of repeatability obtained in the validation phase.  
To evaluate radiological hazard effects, the effective dose for flour ingestion was calculated [39]:  
\[D_{ing}\left(\frac{\mathrm{Sv}}{\mathrm{y}}\right)=h_{ing,K-40}\times J_{ing,K-40} \tag{2}\]  
where \(h_{ing,K-40}\) is the coefficient of the effective dose for the insertion unit for ingestion of \({}^{40}\)K (Sv Bq\({}^{-1}\)), and \(J_{ing,K-40}\) is the intake of \({}^{40}\)K (Bq year\({}^{-1}\)) [40]. The latter value is obtained by multiplying the yearly flour consumption for the mean activity concentration of the investigated radionuclide experimentally measured.