Radiometric evaluation of excessive lifetime cancer probability due to naturally occurring radionuclides in wastes dumpsites soils in Agbara, Southwest, Nigeria

The concentration and spatial distribution of the gamma ray emitting ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs radionuclides in dumpsite soils in Agbara were analyzed with the aim of evaluating the radiation hazards and excessive lifetime cancer risk using well calibrated HPGe γ-ray spectrometry technique. The ranges of activity concentrations of ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs are 11.5 ± 1.0 ↔ 166 ± 40 Bq kg⁻¹, 15.6 ± 1.8 ↔ 31.4 ± 2.3 Bq kg⁻¹, 20.4 ± 1.3 ↔ 366 ± 30 Bq kg⁻¹ and 0.52 ± 0.1 ↔ 8.44 ± 0.2 Bq kg⁻¹ respectively. Radiological parameters such as absorbed dose rate, radium equivalent, annual effective dose equivalent, internal and external hazard indices, gamma level index, activity utilization index, annual genetic significant dose equivalent, exposure rate and excessive lifetime cancer risk were calculated to know the complete radiological hazardous nature of the dumpsite soils to the inhabitants of the sites. The calculated radiological parameters were higher than the world average value in two of the sampling points. The ratio of the detected radioisotopes was calculated for spatial distribution of natural radionuclides in the study area. RESRAD computer code was applied to calculate the total effective dose equivalent (TEDE). The code was also used to calculate the probability of excess lifetime cancer incurred by dwellers/inhabitants of the dumpsites, the level of which was determined to be 0.5 × 10⁻⁴ and 2.5 × 10⁻⁵ for Idowale and Ibijola dumpsite soils over a period of 30 years respectively. Therefore, the radiological risks to the general populations from waste enhanced naturally occurring radioactive materials (WENORM) from the Idowale dumpsite top soils are considered to be significant.