Assessment of natural radioactivity levels in rice samples and their implications for radiological protection

This study investigates the levels of natural and artificial radioactivity in rice samples collected from various local markets in Islamabad, Pakistan. The ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations were measured through gamma-ray spectrometry with a NaI(Tl) detector. The average activity concentrations were 1.67 ± 1.19 Bq kg^-1 for ²²⁶Ra, 3.31 ± 1.83 Bq kg^-1 for ²³²Th, and 88.51 ± 11.65 Bq kg^-1 for ⁴⁰K. Calculated radium equivalent (Ra_eq) values ranged from 7.35 to 18.08 Bq kg^-1, with a mean value of 11.11 Bq kg^-1, all below the permissible maximum of 370 Bq kg^-1. The absorbed dose rates ranged from 6.85 to 16.39 nGy h^-1, with an average of 10.64 nGy h^-1, falling below the acceptable limit of 51 nGy h^-1. The outdoor and indoor radiation hazard indices (H_ex and H_in) had mean values of 0.03, both below the threshold value of one. The external and internal hazard indices (I and I) were both 0.088, also below the critical value of one. The excess lifetime cancer risk (ELCR) ranged from 0.28 to 0.11, with a mean value of 0.18, which is less than the critical value of one. Overall, the radioactivity levels in the analyzed rice samples are within the acceptable limits set by the International Commission on Radiological Protection and are below global averages. These results offer important insights into the radiological safety of rice consumption in the study area.