Radionuclide Concentration and Lifetime Cancer Risk Due to Gamma Radioactivity from Quarry Stone Aggregates in Jos and Its Environs, North Central Nigeria

Abstract

Naturally occurring radionuclides ²³⁸U, ²³²Th and ⁴⁰K present in crushed stone aggregates from seven (7) quarries in Jos and its environs were measured using Gamma Ray Spectrometer. This is mainly for the purpose of evaluating the radiation health hazard indices and excess lifetime cancer risk (ELCR) that may arise due to the use of such crushed stones for building construction. Mean concentration of ²³⁸U, ²³²Th and ⁴⁰K from the quarries were found to be 4.0-15.1 ppm, 25.7-51.7 ppm, and 3.9%-4.4%, while their activity concentration range from 49.5-186.5 Bqkg^-1for ²³⁸U, 104.3-209.9 Bqkg^-1 for ²³²Th, and 1158.1-1471.1 Bqkg^-1for ⁴⁰K respectively. Absorbed dose in air (149.85–264.35 nGy h⁻¹), annual effective dose equivalents for internal and external (0.69-1.22 mSv y⁻¹and 0.23-0.41 mSv y⁻¹), hazard indices (1.00-2.05 indoor, and 0.87-1.53 outdoor), and radium equivalent activity (317.51-573.11 Bqkg^-1) were calculated. These values are higher than the world's averages. Total excess lifetime cancer risk (ELCR) from the quarries was found to be 3.21×10⁻³ - 5.68 ×10⁻³ with an average of 4.45x10⁻³. This is 15.34 times higher than the world average of 0.29x10^-3 below which negligible risk of developing cancer has been stated. Crushed stones from quarries in Jos and its environs therefore may have contributed significantly to cancer risks in this area.

Keywords: Quarry; Crushed Stones; Uranium; Thorium; Potassium; Activity Concentration; Hazard Indices; Excess Lifetime Cancer Risk; Jos Environs..