Radiological Assessment of Maize and Beans Locally Grown Within Bungoma County, Kenya

Cereals and pulses account for a significant portion, more than 34%, of the diet in most Kenyan households. According to estimates, food consumption accounts for at least one-eighth of the mean annual dose due to natural sources of radiation. Naturally occurring radionuclides mainly belonging to Potassium-40, Thorium-232 and Uranium- 238 chains and man-made radionuclides like Caesium-137 find their way into the food chain contributing to both internal radiation dose and environmental radioactivity. Since radioactive nuclides are naturally present in the environment, they may enter the human body primarily by ingesting food contaminated with radionuclides and/or inhaling radioactive particles suspended in the air. Once ingested, radionuclides may accumulate in vital human organs posing a greater health risk due to continuous irradiation. Consumption of contaminated cereal and pulses by radionuclides can lead to severe health problems and adverse consequences. Therefore, it is of great importance to fully understand the risks posed due to intake of these cereals and pulses and determine the key elements that can have an impact these risks to develop prevention measures. This study investigated the presence of the radionuclides ²²⁶Ra, ²³²Th, and ⁴⁰K in maize (Zea mays) and beans (Phaseolus vulgaris) available in Bungoma County. From the study area, eighteen representative samples were gathered. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were determined by gamma-ray spectrometry technique using a thallium activated Sodium Iodide NaI (TI) scintillation detector. Radiological parameters: Absorbed dose rates, radium equivalent, annual effective dose equivalent, external hazard index, and excessive lifetime cancer risk were determined and juxtaposed with the reference levels to establish the risk posed to consumers. The average activity concentration of ²²⁶Ra, ²³²Th, and ⁴⁰K in maize and beans were 20.90±7.19 Bq/kg, 54.00±21.15 Bq/kg, 161.00± 76.84 Bq/kg, and 18.40± 4.03 Bq/kg, 43.00± 15.51 Bq/kg, 195.00± 132.48 Bq/kg respectively. The mean absorbed dose rate for maize and beans were 49.00±2.45 nGy.h^-1and 43.00±2.15 nGy.h^-1 respectively, this was significantly lesser than the admissible dose standard of 57 nGy.h^-1. The average AEID for maize and beans was 1.312 mSvy⁻¹ and 0.263 mSvy⁻¹, respectively. The average values of hazard indices for maize samples were; external hazard index 0.200± 0.081, internal hazard index 0.300±0.081, gamma representative index 0.700±0.206, Excessive Lifetime Cancer Risk 4.89×10^-8. For beans external hazard index 0.200± 0.079, internal hazard index 0.300±0.082, gamma representative index 0.600±0.224, and excessive lifetime cancer risk 1.00×10^-8. The hazard indices were below unity as recommended by International Commission on Radiological Protection (ICRP), implying that ingestion of maize and beans possess minimum threat to consumers and general populace of Bungoma County. The outcomes of this study are significant in building a radiological reference for the cereals and pulses consumed by house-holds and create a sturdy foundation for the establishment of an informed health risk assessment concerning internal exposure to low-energy radiations.