Radiological Exposure of Naturally Occurring Radioactive Materials (NORMs) in Soils at Gold Mining Areas: A Meta-Analysis

Naturally Occurring Radioactive Materials (NORMs), although naturally occurring in the Earth’s crust, become sources of radiological exposure through mining activities. This work provides a meta-analytical assessment of the radiological exposure of NORMs including 232Th, 40K and 238U or 226Ra in soils of gold mining areas. The analysis collates data from various studies on measurement of radiological parameters including Activity Concentrations, Absorbed Dose Rates, Annual Effective Doses, and Radium Equivalent Activities, as well as Internal and External Hazard Indices of different gold mining sites from Nigeria, Kenya, Tanzania and Laos. The studies employed gamma spectrometry using NaI (Tl) detector and decomposition of measured gamma spectra to analyse these parameters from soil samples previously dug out from gold mines. The results showed that while most areas remained within internationally established safety limits, certain sites demonstrated increased radiological risks; especially with regards to 40K and 232Th radionuclides. Sites with high radium equivalent activities approached critical thresholds of safety, and will, thus, require continuous monitoring and perhaps mitigation strategies in order to avoid hazardous levels of radiological exposure to workers and nearby residents. This meta-analysis gives a complete assessment of radiological hazards and provides information on environmental radiation protection in gold mining areas.