Natural Radioactivity Levels and Radiological Risk Assessment of Surface Water from Coastal Communities of Ndokwa East, Delta State, Nigeria

Abstract

Aims: The aim of this study is to measure the natural radioactivity levels in surface water from coastal communities in order to assess the radiological health hazards associated with the use of such water. Study Design: This study was purely an experimental work. Place and Duration of Study: Abalagada, Agwe-Etiti, Asemuku, Aboh and Okpai coastal communities of Ndokwa –East, Nigeria: between April – December, 2016. Methodology: 20 samples of surface water were collected from five coastal communities with pre-washed 2.0 l Polypropylene bottles. The bottles were rinsed with the water before collection and acidified immediately after collection with few drops of HCL. The bottles were sealed tightly with vinyl tapes and kept in the laboratory for 4 weeks for secular equilibrium of the radionuclides. The activity concentration of the radionuclides were measured using Sodium Iodide detector. Results: Activity concentrations of 238U, 232Th and 40K  in surface waters in five communities ranges from BDL to 4.49±1.01 Bql-1 with an average value of 2.37±0.10 Bql-1, BDL to 10.03± 1.04 Bql-1 with average value of 4.19±0.23 Bql-1 and 3.07±0.95 to 34.94±10.77 Bql-1 with an average value of 15.82±2.03 Bql-1 respectively. The activity concentration of 232Th and 40K were higher than their reference values of 1.0 and 10.0 Bql-1. The total effective doses due to ingestion of radionuclides in water are 58.48, 3.195 and 6.243 mSvy-1 for infants, children and adults respectively which are higher than the recommended reference level of 0.26, 0.2 and 0.1 mSv of committed effective dose from one year ingestion of water for infants, children and adults. The estimated lifetime fatality cancer risk to adult shows that approximately 442 out of 10,000,000 may suffer some form of cancer fatality and for the lifetime hereditary effect approximately 274 out of 1000,000,000 may suffer some hereditary effects. Statistical analysis shows that positive correlation exists between the three radionuclides indicating same origin. Conclusion: Oil and gas production activities within the coastal communities has radiologically impacted the surface water of the area and could lead to radiation health risk of public that uses that water.