Assessment of Radiological Health Risks in Agricultural Soil Samples within Bitumen Belt of Ondo State, Nigeria

The quality of agricultural soils within the bitumen deposit areas of Ondo State, Nigeria was investigated with a view to providing valuable information on the radioactivity parameters associated with the contamination of the sites by bitumen deposit. And to provide baseline data required for future radiological impact assessment of the environment during the development of the natural resource. Naturally occurring radionuclides (238U, 232Th and 40K) present in agricultural soil samples collected within the bitumen belt of Ondo State, Nigeria was measured using gamma spectroscopy. The radiological health risk parameters; absorbed dose rate (D), Annual Gonadal Equivalent Dose (AGED), External Hazard Index (Hex), Internal Hazard Index (Hin) and Excess Lifetime Cancer Risk (ELCR) were estimated using standard analytical method. The estimated results of D ranged from 3.56 nGyh-1 (Omotosho) to 10.55 nGyh-1 (Igbotako) with a mean value of 5.83±2.19 nGyh-1. While AGED ranged from 24.07 mSvy-1 (Omotosho) to 70.72 mSvy-1 (Igbotako) with a mean value of 40.39±14.26 mSvy-1. Also, Hex varies between 0.021 (Omotosho) to 0.063 (Igbotako) with a mean value of 0.034±0.01. Similarly, Hin ranged from 0.030 (Omotosho) to 0.089 (Igbotako) with a mean value of 0.047±0.02. However, the estimated ELCR were much lower than the safe limit of 0.29 x 10-3, which suggests that even though there is little radiation risk associated with exposure to natural radionuclides, using the studied soil may not immediately pose a health risk to the locals. However, prolonged exposure may result in radiologically induced health problems.