Natural Radioactivity Levels and Associated Health Risks in Rice Field Soils of Aliaga and Bongabon, Nueva Ecija, Philippines

Soil samples from selected rice farm in the municipalities of Aliaga and Bongabon, Nueva Ecija, Philippines were collected to assess the natural radioactivity levels and associated radiological health risks. Soil samples were analyzed using a high-purity germanium (HPGe) detector to determine the activity concentrations of the primordial radionuclides uranium-238 ( ²³⁸ U), thorium-232 ( ²³² Th), and potassium-40 ( ⁴⁰ K). The measured mean activity concentrations were 2.45 ± 0.05, 2.45 ± 0.47, 158.5 ± 9.2 Bq/kg for ²³⁸ U, ²³² Th, and ⁴⁰ K, respectively. The corresponding absorbed dose rate in air (ADRA), annual effective dose equivalent (AEDE), and excess lifetime cancer risk (ELCR) were 9.3 nGy/h, 0.0113 mSv/y, and 3.975 x 10 − 5, respectively. All measured values were significantly below the global reference levels reported by UNSCEAR (2000), indicating minimal radiological health risk to the local population. Pearson’s correlation analysis showed strong positive associations between natural radionuclide concentrations and radiological risk parameters, while hierarchical cluster analysis indicated that ²³² Th and ²³⁸ U are the primary contributors to external gamma dose, with ⁴⁰ K showing lesser influence. The results confirm that the rice field soils in the study area are radiologically safe for agricultural activities. These findings provide essential baseline data to support continued environmental monitoring and informed land-use planning.