Solid wastes are generated from common manufacturing and industrial processes, and can also be caused by disposing commerce products. The natural radionuclide ( 238U, 226Ra, 232Th and 40K) concentrations in various solid waste samples were determined by using a high pure germanium detector. The obtained average concentration values of 226Ra, 232Th, and 40K in various solid wastes were: Iron (173.29, 141.99 and 32.68 Bq ·kg -1), Copper (2.63, 0.60 and 30 Bq ·kg -1), Aluminum (3.97, 4.89 and 41.67 Bq · kg -1) and in Wood (4.22, 3.11 and 30.20 Bq · kg -1), respectively. The total average values of radium equivalent and the absorbed dose rate were 95.87 Bq · kg -1 and 44.56 nGyh -1, respectively. The effective dose rates in outdoor and indoor average values were 0.05 and 0.20 mSvy -1, respectively. These health hazard parameters were considered to be below the safe limit of UNSCEAR 2000. The presented results show no significant radiological health risks for the workers in the industrial workshops and inhabitance health.
“The occurrence of natural radionuclides 226Ra, 232Th and 40K in industrial solid waste is the source of the radiation hazard to the population and the environment [
Twenty-five of solid waste samples were collected from several Industrial workshops in Saudi Arabia, Jeddah city. The collected samples were oven dried at 110˚C for twelve hours and then packed in a Marinelli beaker and sealed for one month to reach secular equilibrium between 226Ra and 232Th with their decay products. The radionuclide activity concentrations in the prepared samples were measured using a high-purity germanium (HPGe) detector with an efficiency of about 25 %. A counting time of 36,000 s was used for measurements the Gamma-rays spectrum. The background concentration of the γ-rays was determined with an empty Marinelli beaker under the same measurement conditions. 226Ra activities were calculated from the activities of its short-lived daughters 214Pb at 295.2 keV & 351.9 keV and 214Bi at 609.3 keV. 232Th activities were measured by taking the mean activity of photo peaks of the daughter nuclides 228Ac (338.40 and 911.07 keV) and 212Pb (238.63 keV). Activities of 40K were determined directly from its gamma emission at 1460.83 keV.
The activity concentrations of the investigated samples were evaluated using the following equation [
where Nc is the net gamma counting rate (counts per second), ε the detector efficiency of the specific γ-ray, β the absolute transition probability of Gamma- decay and M the mass of the sample (kg).
To assess the radiological hazard of the concerning samples, it is useful to use the radium equivalent activity (Req) in Bq∙Kg−1 [
where ATh, ARa and AK represent the activity concentrations of 232Th, 226Ra and 40K in Bq∙kg?1 respectively. Req is defined according to the estimation that 1 Bq∙kg?1 of 226Ra, 0.7 Bq∙kg?1 of 232Th and 13 Bq∙kg−1 of 40K produce the same gamma-ray dose [
The absorbed gamma dose scale in air 1mabove the ground surface for the uniform distribution of radionuclides (232Th, 238U, and 40K) were computed by guidelines provided by [
where ATh, ARa and AK represent the activity concentrations of 232Th, 226Ra and 40K in Bq∙Kg?1 respectively.
The annual effective dose equivalent received by a member has been calculated from the absorbed dose rate by applying dose conversion factor of 0.7 Sv/Gy and the occupancy factor for outdoor and indoor as 0.2 and 0.8, respectively, [
Excess Lifetime Cancer Risk (ELCR) was calculated by the equation below [
where Deff (outdoor), DL and RF are the outdoor annual effective dose equivalent, the duration of life (70 years) and the risk factor (Sv?1), fatal cancer risk per Sievert. For detriment-adjusted cancer risk of 5.52 × 10−2 Sv?1 for the whole population [
The results of 226Ra, 232Th and 40K concentrations in the waste samples were summarized in
Sample type | Sample code | Radioactivity concentration (Bq/kg−1) | ||
---|---|---|---|---|
226Ra | 232Th | 40K | ||
Iron | F1 | 154.04 ± 4.89 | 162.28 ± 2.27 | 36.51 ± 2.17 |
F2 | 171.34 ± 5.12 | 135.63 ± 2.11 | 35.69 ± 2.0 | |
F3 | 224.53 ± 7.0 | 164.63 ± 2.22 | 46.29 ± 3.21 | |
F4 | 147.38 ± 4.56 | 115.62 ± 2.12 | 17.31 ± 1.12 | |
F5 | 169.16 ± 5.54 | 131.81 ± 2.0 | 27.58 ± 1.6 | |
Average (range) | 173.29 (147.38 ? 22,453) | 141.99 (115.62 - 164.63) | 32.68 (17.31 - 46.29) | |
Cooper | Cu1 | 1.23 ± 0.22 | 0.34 ± 0.02 | 11.94 ± .28 |
Cu2 | 3.26 ± 0.56 | 0.82 ± 0.03 | 45.82 ± 1.78 | |
Cu3 | 1.31 ± 0.08 | 0.98 ± 0.04 | 67.37 ± 2.28 | |
Cu4 | 5.58 ± 0.42 | 0.60 ± 0.03 | 16.37 ± 0.16 | |
Cu5 | 1.79 ± 0.42 | 0.26 ± 0.02 | 8.43 ± 0.42 | |
Average (RANGE) | 2.63 (1.23 - 5.58) | 0.60 (0.26 - 0.98) | 29.99 (8.43 - 67.37) | |
Aluminium | Al1 | 2.76 ± 0.76 | 0.54 ± 0.04 | 23.36 ± 1.14 |
Al2 | 1.56 ± 0.17 | 6.05 ± 1.50 | 36.99 ± 1.61 | |
Al3 | 3.08 ± 0.61 | 2.64 ± 0.86 | 27.91 ± 1.31 | |
Al4 | 7.24 ± 0.73 | 5,12 ± 1.15 | 55.49 ± 2.29 | |
Al5 | 5.23 ± 0.74 | 10.12 ± 2.22 | 64.58 ± 2.65 | |
Average (range) | 3.97 (1.56 - 7.24) | 4.89 (0.54 - 10.12) | 41.67 (23.36 - 64.580) | |
Wood | Wo1 | 1.30 ± 0.22 | 0.27 ± .03 | 10.81 ± .28 |
Wo2 | 10.75 ± 2.31 | 2.46 ± 0.04 | 7.79 ± 0.41 | |
Wo3 | 2.46 ± 0.65 | 3.51 ± 1.33 | 44.57 ± 2.01 | |
Wo4 | 5.56 ± 0.92 | 4.06 ± 0.34 | 72.26 ± 3.13 | |
Wo5 | 1.03 ± 0.03 | 5.25 ± 0.58 | 15.58 ± 0.81 | |
Average (range) | 4.22 (1.03 - 10.75) | 3.11 (0.27 - 5.25) | 30.20 (7.79 - 72.26) |
minerals, also iron scrap were used in high percentage [
The calculated average values of radium equivalent activity (Req), absorbed Gamma Dose Rate (D) and the Annual Effective Dose Equivalent (Deff), for all waste sample types and the total average values are shown in
1) Radium equivalent activity (Req)
The minimum average value of Req activity was 1.12 Bq∙Kg−1 for Copper waste while the maximum average value was 378.86 Bq∙Kg−1 for Iron waste, which is higher than the recommended maximum value of 370 Bq∙Kg−1 [
2) Absorbed gamma dose rate (D)
As shown in
Sample no. | Radium equivalent activity (Bq/kg−1) | Absorbed dose (nGyh−1) | Deff (indoor) (mSv/y) | Deff (outdoor) (mSv/y) | Excess lifetime cancer risk outdoors (CR)×10−3 |
---|---|---|---|---|---|
Iron | 378.86 | 163.86 | 0.73 | 0.18 | 2.54 |
Copper | 1.12 | 2.79 | 0.012 | 0.003 | 0.04 |
Aluminium | 1.70 | 6.54 | 0.029 | 0.007 | 0.10 |
Wood | 1.80 | 5.04 | 0.022 | 0.006 | 0.08 |
Range of average | 1.12 - 378.86 | 2.79 - 163.86 | 0.012 - 0.73 | 0.003 - 0.18 | 0.04 - 2.54 |
Total average | 95.87 | 44.56 | 0.20 | 0.05 | 0.69 |
UNSCEAR 2000 | <370 | 60 | 0.42 | 0.07 | 0.29 |
average and total average values of radium equivalent (in Bq∙Kg) and absorbed dose (in nGyyh−1) for the waste samples under investigation and the recommended values by UNSCEAR 2000.
3) The annual effective dose equivalent
The average annual effective dose of indoor and outdoor for all samples ranged from 0.012 mSvy−1 (Copper) to 0.73 mSvy−1 (Iron) and from 0.003 mSvy−1 (Copper) to 0.18 mSvy−1 (Iron) with the corresponding total average values of 0.20 mSvy−1 and 0.05 mSvy−1, respectively. These average values are less than the world average annual effective dose indoor 0.42 mSvy−1 and outdoor 0.07 mSvy−1 as reported by [
4) Excess lifetime cancer risk (ELCR)
The average values of ELCR ranged from 0.04 × 10−3 in Copper to 2.54 × 10−3 in Iron, with a total average value of 0.69 × 10−3. The average values of ELCR for all waste types are less than the world average (0.29 × 10−3) reported by [
The activities of the natural radionuclides 238U, 226Ra, 232Th and 40K in the solid waste samples collected from various industrial workshops in Saudi Arabia were measured by using a gamma-ray spectroscopy with HPGe detector. The total average values of radium equivalent, external hazard, absorbed dose and effective dose of all studied samples are below the internationally accepted values. The measured samples are still in the zones of normal radiation level, causing no threat to the environment, the human health, and the workers at the workshops except the Iron waste may create some radiological complications. The results may be useful in the assessment of the exposures and the radiation doses due to the natural radioactive content in industrial solid waste samples. They may provide a wide serve as a guideline for future measurement and assessment of possible radiological risks to human health.
We recommend two major steps to be taken into account: first, reducing the hours of operation at the workshops of iron; second, using ventilation and respirators in the workplace at all industrial workshops. Finally, there must be the radiological control on the operation of such industrial workshops.
Al-Zahrani, J. (2017) Gamma Radiation Hazards and Risks Associated with Industrial Wastes Materials. Journal of Geoscience and Environment Pro- tection, 5, 24-30. https://doi.org/10.4236/gep.2017.54003