Radioactivity level of drilled well water across selected cities in Ondo and Ekiti states, Southwestern Nigeria and its radiological implications

Background: The increasing health effects of nuclear radiation occasioned by enhanced human activities in the environment necessitated the need for constant evaluation and assessment of radiological impact on the general populace within a confined developmental area. Hence, Ten (10) drilled well water samples were collected from various cities distributed across Ondo and Ekiti states and analyzed for gamma-emitting radiations. Materials and Methods: The collected water samples were analyzed using n-type co-axial HPGe detector (Canberra Inc, USA), to determine the activity concentrations of the gamma emitting radiations, which was used with dose conversion factors to calculate the age dependent total annual effective dose equivalents to six different age groups and the committed effective dose for the age group >17y. Results: Activity concentrations ranged from 2.25±0.39 to 35.61±6.22 Bq l-1232Th, 7.08±1.71 to 56.68±12.50 Bq l-1226Ra, 45.42±2.98 to 467.61±31.69 Bq l-140K and 1.66±0.46 to 25.55±5.76 Bq l-1232Th, 4.90±1.08 to 54.18±13.34 Bq l-1226Ra, 41.50±2.89 to 558.82±31.69 Bq l-140K, respectively for Ondo and Ekiti States . Furthermore, the mean total annual effective dose equivalent for the age groups was found to be within the range of (2.81 ± 0.46 – 26.91 ± 5.11) mSv/y and (4.71 ± 0.92 – 23.58 ± 5.12) mSv/y respectively for Ondo and Ekiti states. Conclusion: This is above the 1.0 mSv y-1 and 0.1mSv y-1 respectively set by ICRP and WHO. Hence, the drilled wells are recommended for water screening to remove radionuclides.