Inventory of Occupational Risk from Natural Occurring Radioactive Materials (NORMs) in Soil Samples of the Coastal Region of Nigeria After Six Decades of Oil and Gas Exploration

Background and Objective: The occupational risks associated with exposure from radioactivity concentration of soil from oil and gases producing coastal areas of Nigeria have been assayed after sixty years of exploration activities in the area, to ascertain the radiological impact on the oil field workers and host communities. This study observes the occupational risk from natural occurring radioactive materials in soil samples. Materials and Methods: Gamma spectrometric technique was used to determine the radiometric in the soil samples collected using highly efficient thallium activated 3"×3" gamma spectrometer. Results: The mean activity concentration of the three natural radionuclides of ⁴⁰K, ²³⁸U and ²³²Th are 1586.82±17.97, 27.26±8.38 and 37.67±9.55 Bq kg^–1, respectively. The occupational risk estimates from three exposure routes, external, inhalation and ingestion were calculated using the specific activities of the radio nuclides detected in the soil samples. Radioactivity concentrations measured in the communities were found to be higher than their corresponding standard values. The estimated total effective dose received by the residents and oil field workers through the three exposure routes ranged from 0.2-14.8 mSv y^–1 with a mean value of 4.77 mSv y^–1. The values of each of the total effective doses estimated in the different communities exceeded the 1.0 mSv y^–1 permissible limit. The dose equivalent estimate obtained for external exposure is 4.27 μSv y^–1 which represents 89.0% of the permissible limit. Conclusion: These results obtained show that both residents and oil field workers are significantly exposed to radiation from the soil which may be of radiological health concern.