Monitoring and Health Risks Assessment of Primordial Radionuclides in Vegetables and Agricultural Soils in Some Hilly Regions of Southeastern Bangladesh.

Abstract

This study demonstrates the naturally occurring radioactive materials (NORMs: ²²⁶Ra, ²³²Th, and ⁴⁰K) in vegetables and their corresponding agricultural soil samples collected from southeastern Bangladesh (Chittagong). Elemental abundances measured by neutron activation analysis have been converted into associated radioactivities. Mean_n=30 specific radioactivities of ²²⁶Ra, ²³²Th, and ⁴⁰K in soil were 43.5, 61.5, and 645.2 Bq kg^-1, respectively, which were relatively higher compared to the corresponding recommended values. Activities of NORMs in vegetables (edible parts) ranged (Bq kg^-1) from 1.75 to 16(²²⁶Ra), 0.8-23.09(²³²Th), and 174-1743(⁴⁰K), which were higher than the corresponding recommended values, respectively. Higher radioactivity in the studied vegetables is mostly attributable to the fertilizer usages (specifically phosphate, potash, and organic fertilizers) and irrigation processes. Average_n=9 transfer factors of ²²⁶Ra, ²³²Th, and ⁴⁰K for under-surface vegetables (e.g., potato) were 0.078, 0.0933, and 0.799, whereas their average_n=21 TFs for over-surface vegetables (e.g., tomato) were 0.078, 0.102, and 1.5, respectively. Human health concerns are demonstrated by estimating standard radiological-risk indices. The cancer risks of the tomato sample surpass the allowable limit (3.5 × 10^-3 Sv^-1). Estimated ingestion dose was higher in tomato, okra, yardlong bean, and eggplant compared to the corresponding world average (290 µSv y^-1). Ingestion of NORMs through the uptake of vegetables can cause severe damage to the different tissues of digestive system by receiving alpha-radiations from the decay products of ²³⁸U and ²³²Th. Optimized usages of chemical fertilizers, crop rotation, and elevated use of organic compost fertilizers are recommended for controlling the NORMs abundances in the edible part of the vegetables.