Khandoker Asaduzzaman

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.

The distribution of natural series radionuclides ²²⁶Ra, ²³²Th and non-series ⁴⁰K in the heavy mineral-rich beach sands of highly touristic areas of Cox’s Bazar sea beach has been studied. The study is made to evaluate the gamma radiation exposure to individuals with an aim to establish reference data for the presence of naturally occurring radionuclides. The present study reports the probable first attempt of detail and systematic work in the study areas for estimation of activity concentration in the recent beach sand samples. Radiometric analysis was performed using gamma ray spectroscopy system based on HPGe detector. The mean activity levels of ²²⁶Ra, ²³²Th and ⁴⁰K in Laboni beach sands were ranged from 255.69±64.57, 336.83±93.96 and 1785.91±89.60 Bq kg^-1, respectively. While in Kolatoli beach sands, the respective values were 166.42±35.99, 157.35±35.90 and 1894.42±74.07Bq kg^-1, respectively. The mean values of ²²⁶Ra and ²³²Th concentrations in the investigated beach sands were estimated to be very much higher than the corresponding world average values and comparable to those found in high background radiation areas in the world. The heavy minerals seem to control the activity concentrations of ²²⁶Ra and ²³²Th in sand samples, showing some variances based on uranium and thorium bearing minerals. Various radiation health hazard indicators were found to be extremely higher when compared to the recommended values. Hence, heavy mineral-rich sands may pose a significant radiological health risk to the people. The descriptive statistics indicating the radionuclides of ²²⁶Ra, ²³²Th and ⁴⁰K are uniformly and symmetrically distributed in the Cox’s bazar beach sand. Multivariate statistical analysis showing the radioactivity and estimated radiological parameters are strongly positively correlated with ²²⁶Ra and ²³²Th, while weakly correlated with ⁴⁰K, signifying that radiological risk is mainly associated and controlled by the radioactivity levels of uranium and thorium series radionuclides.

The concentration of natural radioactivity in rice is an important parameter for the determination of population exposure by the ingestion of natural radionuclides during habitual consumption of food. All types of food including rice contain a detectable amount of natural radioactivity which successively relocate into the human body via the ingestion pathway. Rice is the main cultivated crop in Bangladesh and most of the Bangladeshi people consume rice as their staple food. Hence, studies on the evaluation of natural radioactivity in rice have been performed by gamma-ray spectrometry using High Purity Germanium (HPGe) detector in order to estimate various radiation hazards due to rice consumption. The average activity levels of natural radionuclides ²²⁶Ra, ²²⁸Ra and ⁴⁰K in the rice samples were 1.09 ± 0.31, 0.17 ± 0.21 and 4.70 ± 1.59 Bq kg⁻¹, respectively. The estimated effective doses for the respective radionuclides caused by the rice consumption were 43.69, 16.39 and 4.15 µSv y⁻¹, respectively which was below the UNSCEAR compiled value. The calculated excess lifetime cancer risk (ELCR) values via rice consumption were found below the acceptable limit of 0.29 × 10⁻³ for radiological risk.

Technical benefits relevant to the use of palm oil clinker (POC) and fuel ash (POFA) in building materials has been well documented. However, the radiological health hazards caused by the incorporation of POC and POFA as an ingredient of building materials have not been studied so far. The radioactivity levels were measured by γ-ray spectrometry using hyper-pure germanium (HPGe) detector. The activity concentration of ²²⁶Ra and ²³²Th in POC and POFA was found to be in the ranges of 5.56 ± 0.23 to 9.03 ± 0.21 and 4.21 ± 0.03 to 7.98 ± 0.19 Bq kg⁻¹, respectively, and these values were lower than the world average values of 50 Bq kg⁻¹ for building materials. The ⁴⁰K value was within the range of 413.01 ± 1.78 to 604.66 ± 2.18 Bq kg⁻¹. Several radiological parameters and hazard indices, i.e. radium equivalent activity, absorbed dose rate and annual effective dose etc. were calculated for the evaluation of the potential radiological hazards. The obtained values fall within the recommended limit set by various international organizations. Since the activity levels of ²²⁶Ra, ²³²Th and ⁴⁰K in POC and POFA were significantly lower than the corresponding literature data for other ingredients of building materials, it indicates that POC and POFA are safe to be used in concrete construction.

This work presents radiological data on most commonly sold bottled water brands in the urban areas of Bangladesh. A significant fragment of the population use bottled water as their source of daily water intake. It is known from the literature that some varieties of bottled waters contain natural radionuclides in higher concentration than the traditional municipal tap water. In this study, concentrations of naturally occurring radioactive materials, particularly ²²⁶Ra, ²²⁸Ra, and ⁴⁰K, and its annual effective dose with its stochastic effects were determined in available brands of bottled mineral water manufactured in Bangladesh. The measurement was performed by gamma-ray spectroscopy using a hyper-pure germanium detector. The activity concentration of the radiologically important nuclides ²²⁶Ra and ²²⁸Ra were found within the permissible limits of 1 and 0.1 Bq l⁻¹, respectively, recommended by World Health Organization (WHO) in almost all samples. The annual effective doses caused by natural radioactivity of ²²⁸Ra for the infants (0–1 year) and adolescent (12–17 year) groups exceeded the recommended WHO guideline level of 0.1 mSv y⁻¹ for drinking water in most of the cases. Particularly for those age groups, the estimated doses are extremely high. In general, the carcinogenic risk due to natural radioactive doses for all bottled water samples were found below the acceptable limit of 10⁻³.