Health risk assessment of radiation dose of background radionuclides in quarry soil and uptake by plants in Ezillo-Ishiagu in Ebonyi South-Eastern Nigeria

Abstract

Natural origins of radioactive elements are present in different concentrations in the environment as well as granite quarry depending on the geological formation of the soil. The bio-concentrations of these elements in plants are hazardous to the environment and human health. This study presents the evaluation of the activity concentration of radionuclides in granite quarry soil and bio-accumulation in plants from Ishiagu and Ezillo using gamma ray spectrometry. The average activity concentration of 238U, 232Th, 40K in Ishiagu granite quarry soil were (22.5; 13.7; 141.3) Bq/kg, that of Ezillo (15.7; 11.9; 128.2) Bq/kg, whereas in plants ranged from (BDL – 34.3; 1.3–4.0; 73.4–260.7) Bq/kg for Ishiagu and (1.8–20.6; 0.1–5.0; 61.7–171.5) Bq/kg for Ezillo. The mean radium equivalent (Raeq), dose rate (DR), internal hazard index (Hin), external hazard index (Hex), gamma index (Iγ), alpha index (Iα), indoor annual effective dose (AEDRin), outdoor annual effective dose (AEDRout) and excess lifetime cancer risk (ELCR) were all determined to assess the radiation hazard of the quarry soil. The results of the radiological parameters were below the permissible limit and may not pose a radiological risk when used as building materials. The average AED and ELCR for ingestion of plants at Ishiagu and Ezillo were (0.0811mSvy−1, 0.283 × 10−3) and (0.0731mSvy−1, 0.255 × 10−3). Some plants depicted a high level of ELCR >0.29 × 10−3 leading to the possibility of radiological health threats from continual consumption of these plants. The radionuclides transfer factor showed higher values for 40K in the order: 40K > 238U > 232Th, implying high bio-concentration of 40K in the plants. There are potential radiological health threats to the public from the long-term consumption of plants cultivated within and around the quarry locations. Therefore, the study areas may on the long run not be safe for residents, hence radioactivity concentrations should be monitored to avoid environmental health implications of accumulated gamma dose.