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Analytical Evaluation of Inhalation Dose from Residual Radioactivity to Offsite Residents in Nigeria using ICRP Age Dependent Dose Coefficients. |
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PP: 183-191 |
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doi:10.18576/jrna/080212
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Author(s) |
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Soja Reuben Joseph,
Nasiru-Deen Adebayo Bello,
Umar Ibrahim,
Nuraddeen Nasiru Garba,
Muhammad Bello Gusau,
Abdullahi A Mundi,
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Abstract |
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| One of the primary means by which people are exposed to radionuclides with prolonged half-lives such as 238U, 232Th and 40K is mining, which involves physically removing minerals from the earths surface. This study performed analytical evaluation of inhalation dose from residual radioactivity arising from mining activities to offsite residents using ICRP age dependent dose coefficients for five different age groups; 1 Year, 5 Years, 10 Years, 15 Years and Adult age groups respectively. In order to estimate age-dependent inhalation dose using analytical technique, data on measured activity concentration of NORMs radionuclides, comprising of 238U, 232Th and 40K in soil samples obtained from selected mining areas were extracted from previous literatures along with their methods of analysis. Sixteen (16) mining sites, randomly selected across Five (5) Geopolitical zones of North East, North West, North Central, South West and South Eastern Nigeria respectively. The highest inhalation dose was recorded in Gura top mining site in Jos Plateau state, North Central geographical region with annual inhalation dose of 6.06E-02 mSv/yr, 9.51E-02 mSv/yr, 1.10E-01 mSv/yr, 1.40E-01 mSv/yr and 1.46E-01 mSv/yr while the lowest inhalation dose was recorded in Itagunmodi mining site in Osun, South West region with annual inhalation doses of 5.01E-03 mSv/yr, 7.36E-03 mSv/yr, 8.36E-03 mSv/yr, 1.05E-02 mSv/yr and 1.07E-02 mSv/yr for all age groups considered in this study. The higher inhalation dose are reported from 238U and 232Th than 40K due to gaseous decay of radon and thoron which are harmful when inhaled and deposited in the human respiratory tract system. All the inhalation doses reported falls below the United State Environmental Protection Agency (US-EPA) recommended dose limit of 0.1mSv/yr from release of aerosol, and International Commission on Radiological Protection (ICRP) dose limit of 1 mSv/yr for the public, demonstrating that the short-term effects of inhaling radiation from mining sites on offsite dwellers are minimal. However, it is important to note that the ICRP are based on the thoughtful assumptions that there is no safe level of radiation exposure since the accumulation of small doses of radiation can have unpredictable effects. The offsite dwellers living within the vicinity of the mining site need to be conscious of the dangers of radiation exposure and its repercussions. To minimize the severity of exposure in accordance to the “As Low As Reasonable Achievable” principle and also to ensure strict adherence to radiation protection, routine assessment of exposure dose from mining activities to both onsite and offsite dwellers is recommended. |
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