Radiogenic Components of Limestone Samples Collected from Ewekoro SW Nigeria: Implications for Public Radiological Health Risks Assessment and Monitoring

AIM: This research presents the radiogenic components in thirteen limestone samples from a quarry site in Ewekoro, southwestern Nigeria. METHODS: The distributions of natural radionuclides ((238)U, (232)Th and (40)K) in the limestone samples were determined by gamma spectroscopy using a well-type thallium-doped sodium iodide detector. Also, estimated associated radiological hazards are presented and compared with the standard threshold values. RESULTS: The activity concentrations for (238)U, (232)Th and (40)K radionuclides range 18.09 ± 3.43-239.50 ± 25.74 Bqkg-1, 8.33 ± 0.83 - 360.01 ± 21.33 Bqkg-1 and 11.28 ± 0.81-735.26 ± 0.95 Bqkg-1 respectively. The radium equivalent activity concentration in the samples ranges 58.857-758.832 Bqkg-1 with samples S3, S4 and S11 values higher than the threshold limit of 370 Bqkg-1. Estimated dose rate and annual effective dose rate (AEDE) from the samples have ranges 28.754-330.917 nGyh-1 and 35.26-405.84 μSvy−1 respectively greater than the standard limit of 59 nGyh-1 and 70 μSvy−1 respectively for all samples except S9. The estimated external and internal indices are ranging 0.16 – 2.05 and 0.21 – 2.68 respectively, greater than permissible unity in some limestone samples such as S3, S4, S8, S11 and S13. Excess lifetime cancer risk was also computed using a life expectancy of 54.5 years. The results of higher radiological parameters in the limestone samples revealed that the miners have a high probability of contracting induced cancer. CONCLUSION: A regular check-up is recommended for the miners and staffs within the quarry site. Also, the residents within the environs should be relocated far away from the quarry site, as the particulates from the limestone rock blasting could contaminate the air in the study area.