Assessment of environmental radioactivity and radiological hazard indices in soil and water around a nuclear medicine institute in Bangladesh.

This study assessed the activity concentrations of natural and artificial radionuclides and evaluated the associated radiological risks in soil and surface water samples collected from the Institute of Nuclear Medicine and Allied Sciences (INMAS) and the hospital premises of Rajshahi Medical College Hospital (RMCH), Bangladesh. Gamma-ray spectrometry and ArcGIS-based spatial mapping were employed to evaluate radiological conditions and associated health risks. The analysis included measurements of 226Ra, 232Th, 40K, 137Cs, 60Co and 131I in ten soil and ten water samples. The results demonstrated spatial variation in radionuclide distribution, although most values remained within internationally accepted radiological safety limits. In soil, mean activity concentrations at INMAS were 36.30 ± 6.52 Bqkg-1 (226Ra), 60.09 ± 8.64 Bqkg-1 (232Th), and 517.84 ± 55.23 Bqkg-1 (40K), exceeding those at RMCH (22.91 ± 6.17, 44.33 ± 8.11, and 468.45 ± 35.17 Bqkg-1, respectively). The distribution pattern (40K > 232Th > 226Ra) aligned with typical alluvial sediment geochemistry. In water, INMAS recorded lower activity concentrations of 226Ra (1.70 ± 0.19 Bqkg-1) and 232Th (2.14 ± 0.27 Bqkg-1) than RMCH (6.74 ± 1.08 and 5.33 ± 1.37 Bqkg-1, respectively), while 40K remained below detectable levels. No anthropogenic radionuclides (137Cs, 60Co and 131I) were detected of the gamma spectrometry system. Although certain soil samples exhibited outdoor absorbed dose rates, annual effective doses and excess lifetime cancer risk values slightly above global averages, others evaluated radiological hazard indices, including radium equivalent activity, external and internal hazard index, remained within internationally accepted safety limits for both soil and water. Scientific analysis confirms that the radiological profile of the Rajshahi medical-urban nexus is governed strictly by natural terrestrial radionuclides rather than medical-industrial discharges. Consequently, this study establishes a pristine "zero-point" radiological archive that is essential for distinguishing future industrial emissions from the existing geogenic background once the Rooppur Nuclear Power Plant becomes operational.