Evaluation of radiological risk associated with local building materials commonly used in Northwestern Nigeria

In this study, potential radiological risk due to the activity concentrations of primordial radionuclides (226Ra, 232Th, and 40K) in commonly used local building materials (sand, clay, kaolin and gypsum) in Northwestern Nigeria were assessed using NaI (Tl) detector. The measured activity concentrations ranged from 47 to 63 Bq kg-1 for 226Ra, 24-32 Bq kg- 1 for 232Th, and 219-257 Bq kg- 1 for 40K respectively. The mean values of 232Th, and 40K for all samples were below the respective world averages of 45 and 420 Bq kg- 1 with that of 226Ra for all the samples higher than the world average value of 32 Bq kg- 1. The potential radiological risks were assessed by determining radium equivalent activity (Raeq), internal and external hazard indices (Hin and Hex), absorbed gamma dose rates (DR), internal annual effective dose rates (IAED), and annual gonadal dose equivalent (AGDE) and activity utilization index (AUI). The assessed parameters were found to range between 104 and 125 Bq kg- 1, 0.99 to 1.15, 0.28 to 0.34, 48 to 58 nGyh-1, 0.76 to 0.86 mSvy- 1, and 0.78 to 0.96 respectively. The Raeq and DR for all the analyzed samples were found to be within International recommended limits of 370 Bq kg- 1 and 59 nGy h-1 as recommended by UNSCEAR.