Radiological risk assessment of farm-raised fish species due to natural radionuclides in the freshwater ecosystem of Bangladesh with the statistical approach

Abstract

We study radiation exposure resulting from the consumption of farm-raised freshwater fish species that form an essential part of the Bangladeshi diet. The levels of radioactivity in the human diet are of particular concern, requiring assessment of possible radiological risks to human health. Therefore, a comprehensive study was carried out to determine the radioactivity levels (226Ra, 228Ra, and 40K) in fifteen commonly available varieties of farm-raised fishes. The gamma-ray spectroscopic analysis showed the presence of radionuclides of 226Ra, 228Ra, and 40K in all studied fishes, but varying degrees. The highest radioactivity levels of 226Ra, 40K, and 228Ra were observed in Rui (Labeo rohita) and Tilapia (Oreochromis mossambicus) with values of 8.50 ± 0.30, 513.28 ± 1.59, and 7.41 ± 0.15 Bqkg−1, respectively. The respective radioactivity levels were lowest in Silver carp (Hypophthalmichthys molitrix), Mola (Amblypharyngodon mola), and Koi (Anabas testudineus) with values of 0.83 ± 0.38, 171.07 ± 1.60, and 0.62 ± 0.30 Bqkg−1. The doses for 226Ra, 228Ra, and 40K due to consumption of a kilogram of farm fish were assessed and range from 5.56 (Sarputi – Puntius sarana) to 54.36 µSvy–1 (Rui – Labeo rohita), 9.77 (Koi – A. testudineus) to 116.79 µSvy–1 (Tilapia – O. mossambicus), and 24.23 (Mola – A. mola) to 72.69 µSvy–1 (Rui – Labeo rohita), respectively. In most cases, the estimated probability of an increase of cancer risk from daily intake of the farm-raised fish diet representing a minor fraction of ICRP values. Statistical analysis shows that the radioactivity and estimated radiological parameters are strongly correlated with 226Ra and 228Ra, while weakly correlated to 40K, suggesting that radiological risk is basically associated and controlled by the activity levels of uranium and thorium series radionuclides.