Radiological risk assessment of naturally occurring radioactive materials (NORMS) from selected quarry sites in Edo State, South-south, Nigeria

This study was carried out to evaluate activity concentrations of naturally occurring radioactive materials (NORMs) to assess the distribution of 226 Ra, 232 Th, and 40 K in selected quarries in Edo State, South-south, Nigeria and to appraise the radiological hazard they may pose to the general public when used as building material. Twenty five (25) quarry samples were collected from five (5) selected quarries in the study area and their activity concentrations were measured using gamma-ray spectroscopy technique. The radiological hazard parameters: radium equivalent activity, absorbed gamma dose rate, internal and external hazard indices and annual effective dose were also determined. The average activity concentrations of 226 Ra and 232 Th from all the quarries are observed to be higher than internationally recommended value. The average activity concentrations of 40 K from two quarries were found to be below the internationally recommended value while it is higher in the remaining three quarries. The results also revealed that a couple of the calculated radiological hazard parameters are higher than permissible limit, hence, such quarry products may pose a radiological risks to the exposed population when used as building construction material. Correlation matrix for the activity concentrations of the NORMs and all the radiological variables is presented to determine the correlation between the variables in various samples.