Estimation of radiation dose and cancer risk from ingestion of natural radionuclides in groundwater of Ekiti State, Southwest Nigeria

Groundwater contains natural radionuclides in varying concentrations and its consumption may present a risk to human health. To evaluate the radiation dose due to the ingestion of the radionuclides in groundwater, 100 groundwater samples from wells used for drinking purposes were obtained spatially across Ekiti State. The concentrations of 226Ra, 232Th, and 40K were measured using a calibrated thallium-doped sodium iodide scintillation detector. The average values of the radionuclide concentrations in the drinking water samples are 4.1 & PLUSMN; 3.4 Bq L-1, 3.4 & PLUSMN; 1.6 Bq L-1, and 62.6 & PLUSMN; 44.0 Bq L-1 for 226Ra, 232Th, and 40K respectively. Most of the groundwater samples have radionuclide concentrations above the WHO guidance level for the three radionuclides. The estimated average radiation dose due to ingestion of radionuclides in the groundwater to adults, children, and infants are 971.48 & mu;Sv y-1, 680.03 & mu;Sv y-1, and 291.44 & mu;Sv y-1 respectively. The lifetime cancer risk values of 1.05 x 10-3 and 1.10 x 10-3 due to ingestion of radionuclides in groundwater were evaluated for male and female respectively. These risk values are considered to be significant. Remedial actions may be necessary to ensure the safe consumption of groundwater in the area.