Concentrations and Radiation Hazard Indices of Naturally Radioactive Materials for Flour Samples in Baghdad Markets

In the present work, Uranium ( 238 U), Thorium ( 232 Th) and Potassium ( 40 K) specific activity concentration in (Bq/kg) was measured in five different types for wheat flours that are available in the Iraqi markets. The gamma spectrometry method with an NaI (Tl) detector has been used for radiometric measurements. Calculations of radium equivalent activity, annual effective dose equivalent, external hazard index (Hex), internal hazard index (Hin), representing gamma index and gamma dose rate in all flour samples were 17.98132 Bq/kg, 0.0100334, 0.04502, 0.04857, 0.06872, 0.125883 and 8.181244 respectively. It is found that the average of specific activity concentration of wheat flour samples for 238 U, 232 Th and 40 K are 7.4564 Bq / kg, 6.27962 Bq / kg and 20.0658 Bq / kg respectively. This study proves that the natural radioactivity and radiation hazard indices were lower than the safe.


Introduction:
Because of geographical and geological conditions, the natural radionuclide concentrations in environmental samples can be significantly various. Natural radioactivity can be classified into two types, cosmogenic and primordial, named naturally occurring radioactive materials, commonly mentioned as (NORM). Some instances of natural radioisotopes are potassium isotopes 40 K, uranium ( 238 U and glycolysis chain), and thorium ( 232 Th and glycolysis series). These radionuclides are generally available in air, soil, and water in diverse magnitudes, in addition to their long-lasting period (for about 1010 years) (1)(2)(3). In order to provide enough food to the increasing populations, several states have utilized phosphate fertilizers; these activities have triggered a substantial alteration in potassium in the soil, which makes significant changes to these agricultural activities. By means of the soil and phosphate utilizers, natural radioactive elements transfer through the food chain to humans. In order to avoid consumer vulnerability to radiation, it was substantial to measure the radioactivity of some food samples in order to identify the anticipated radiation doses. As well-known, potassium is deemed to be one of the bulk substantial fundamental elements admitted into the cellular tissues, so 40 K is one of the bulk substantial physical radionuclides (4). About 87% of the radiation dose sucks by humanity is from natural radiation according to UNSCEAR 2000 (5). Wheat flour is considered as one of the substantial foods in Iraqis daily lives. It is appropriate to compose a national baseline of radioactivity exposure from various type wheat flour samples available in Iraq markets. Wheat flour is produced from grinding wheat used for human consumption. Wheat flour has been a fundamental staple to human presence across the centuries and is currently the more broadly expendable staple food. Additionally, several studies have been performed worldwide to inquire the natural radionuclides in food consumer in various areas of the world (6-9). By spectroscopic analysis, the concentration of natural radionuclides ( 40 K, 232 Th, 226 Ra) is computed in diverse foods for human depreciation in the Abyan Delta in Yemen and it was found that the modified concentrations of radionuclides of 226 Ra, 232 Th, and 40 K in the selected specimens were 1.11 ± 0.08 , 1.00 ± 0.05 and 108.86 ± 3.49 , respectively. It was remarked that the modified concentration of 40 K activity in foods was substantially of a superior activity to the modified concentrations of 226 Ra and 232 Th in all the samples (10)(11)(12).
The aim of the current work is measuring natural radioactivity concentrations for flour samples; Besler, Zer, Paten, Flour provided by government and barley in the local markets of Baghdad city in 2019, three samples of each type for flour were taken. Also, it calculated radium equivalent activities, annual effective dose equivalent, external and internal menace indices, representing extent index, and the gamma dose rate using a gamma spectrometry, NaI (Tl) detector. Then, it estimated the radioactivity and its effect on human health. This study is necessary in the standpoint radiation protection and discusses natural radioactive elements in food coverage by the humans.

Specific activity concentration
The specific activity concentration is the relationship between the mass of the material and its radiation efficiency in Bq/Kg, which is the number of anomalies that occur per second in radionuclide, it is given by Eq. 1 (13,14): S.A=C= A / M 1 Terms A is the activity which is identified directly from the screen of the system in Bq, M is the mass of sample in Kg.
Samples like Besler, Zer, Paten, Flour are provided by government and barley in the local markets of Baghdad city in 2019 .Gamma spectroscopy with Sodium iodide (NaI (Tl)) (3" X 3") detector was adjusted for a period of 3600 seconds, and completely insulated by lead shield (13) used to determine NORM concentrations, in flour powdered samples. The weight of each samples are is Kg. Because the NaI (Tl) detector is characterized by poor efficiency in energy resolution, radionuclides daughter was selected to determine radioactivity concentration for two series of 238 U and 232 Th where nuclide 226 Ra was chosen to indicate the radioactivity for a series of 238 U, which have been determined through radioactive isotope 214 Pb (352keV). Moreover, a series of 232 Th through a radioactive isotope 212 Pb (239keV) was determined. As regards 40 K (1460.8 keV), it can be detected directly by the detector (4,13,14).

Radium Equivalent Activity (Ra eq )
Radium equivalent activity Ra eq which is the equivalent concentration value of the radium element is used to study the risk concentration caused by 226 Ra, 232 Th and 40 K (Bq/Kg). In addition, the radiation hazards associated with them were taken into account and can be calculated from the following relationship as show in Eq.2 (15). Ra eq = C (Ra) + 1.43 C (Th) + 0.077 C (K ) 2 Where C (Ra) , C (Th) and C (K) represented radioactivity concentration in (Bq/Kg) for 238 U, 232 Th and 40 K, respectively.

Annual Effective Dose Equivalent (AEDE)
Dose equivalent receipt by the external member was computed from the absorbed dose rate through implementing the dose conversion of 0.7 (Sv/Gy) and the internal and external occupancy factor will be 0.2(5/24) and 0.8(19/24), respectively (13,15). AEDE is determining by the Eqs.3 and 4.

External Hazard Index (H ex )
This hazard can be quantified by the external hazard index (H ex ) (13,15,16). which is determined by Eq. 5: The value of this index should be lower than one unit for the radiation hazard to be minimal. H ex equals to unity that is symmetrical for the high limit of Ra ( eq ) 370 (Bq/Kg) (13).

Internal Hazard Index (H in )
This hazard can be quantified by the internal hazard index (H in ) (13,15,16). This is given by Eq. 6: The value of this index should be lower than one unit for the radiation hazard to be minimal.

Representative Gamma Index (I γr )
The representative gamma index is given by Eq.7 (17): Value of I γr ≤ 1 complies to an annual effective dose, of lower than or equal to 1.0 (mSv), while the I γr ≤ 0.5 complies to annual effective dose lower or equal to 0.3 (mSv) (17,5)

Results and Discussion:
238 U, 232 Th and 40 K are naturally occurring elements. Their nuclei of radioactive elements are unstable, meaning they are transformed into other elements, typically by emitting particles. Uranium decays mainly by alpha-particle emission to become nonradioactive lead and it has very long half-lives. In the case of 40 K, it undergoes beta decay to stable species ( 40 Ca) and for 232 Th they undergo alphadecay to stable species ( 228 Ra) (13). The specific activity concentration due to 238 U, 232 Th and 40 K in various types of wheat flour samples has be measured as shown in Table 1  Bq/Kg in flour provided by government to 6.109 Bq/Kg in zer flour. The results obtained shows that, the concentration of specific activity for 238 U, 232 Th and 40 K in all samples for flour was lower than the recommended limit of UNSCEAR 2000 which is 30, 45 and 420 Bq.kg -1 , respectively (5). The value of radium equivalent activities, annual effective dose equivalent, external and internal menace indices, representing extent index, and the gamma dose rate for all flour samples are listed in Table 2. The maximum value of radium equivalent activities, annual effective dose equivalent, external and internal menace indexes representing level index, and the gamma dose rate was found in barley flour sample and the minimum value of these indexes was found in zer flour sample. The results was lower than the recommended limit of UNSCEAR 2013 (18) which is 0.17 mSv y -1 for 40 K and 0.12 mSv y -1 for Uranium and Thorium. High intake of 232 Th, 238 U, 40 K and their decay products may lead to harmful effects in human beings. An exposure of about 0.1 mg.Kg -1 form body weight of soluble natural Uranium, Thorium and Potassium results in transient chemical damage to the kidneys (19). All the results obtained from this study are in agreement with the previous studies (4,20).    2 shows the average value of Ra eq of gamma dose rate for all samples were determined using Eq.2. The maximum value of gamma dose rate was 24.02987 Bq/Kg in barley flour and the minimum value of radium equivalent activities was 17.98132 Bq/Kg in zer flour sample.

Figure 2. The Ra eq for flour samples.
The average values of the (AEDE), calculated using Eqs.3,4 in units of mSv/y. by using 0.8 for the outdoor occupy factor, which implies 20% of time is spent outdoors, while for the indoor occupy factor 0.2 is used, which is suggested by UNSCEAR 2013 respectively (18). The average value of the AEDE reason to wilderness gamma radiation internal and external received for flour models was 0.04013 and 0.01003 (mSv/y). The maximum value for AEDE internal was 0.05324 (mSv/y) in barley flour samples and for AEDE external was 0.01331(mSv/y) in barley flour samples. The minimum value for AEDE internal was 0.03113 (mSv/y) in the zer flour samples and for AEDE external was was 0.00778 (mSv/y) in the zer flour samples, as shows in Figs. 3 and 4.

Conclusions:
As commented on before, 87% of the radiation dose is due to natural radiation sources .Essential shareholders existed by the present work are 238 U and 232 Th, that have activities in the same order as in the literature for 226 Ra and nearly twice as high for 232 Th. The world average values of 238 U, 232 Th and 40 K concentrations indicated for natural background areas are 30, 45 and 420 Bq.Kg -1 , respectively. The result values found are lower than the average values. Due to increasing employment of phosphate fertilizers in agriculture, potassium substance in soils can be changed and conveyed via food chain to man. As the metabolic balance maintains the 40 K body level irrespective of intake quantities, since the metabolic balance sustain the 40 K body level regardless of intake quantities, so the quantity of 40 K , which is 1.17.10 -4 of the natural plethora, will be also approximately constant. The annual 40 K equivalent dose in tissues of the body is 165 μSv.y -1 for adults and the total 40 K effective dose from inhalation and ingestion is 170 μSv (5). Because of this, there is no trouble in swallowing cereal flour providing the activities levels existed in the present work.