Natural Radioactivity Levels and Radiological Risk Assessment in Locally Grown Maize and Beans from Bungoma County

Abstract

This study investigated the concentration of 226Ra, 232Th, and 40K in maize (Zeamays) and beans (Phaseolus vulgaris), the common cereals and pulses available in Bungoma County. Eighteen representative samples were collected from the study area and analyzed using a Thallium-activated Sodium Iodide NaI (TI) scintillation detector. The average activity concentration of 226Ra, 232Th, and 40K in maize were found to be 20.9 ± 7.19 Bq/kg, 54 ± 21.15 Bq/kg, and 161 ± 76.84 Bq/kg, while in beans, these values were 18.4 ± 4.03 Bq/kg, 43 ± 15.51 Bq/kg and 195 ± 132.48 Bq/kg respectively. The mean absorbed dose rates were 49 ±2.45 nGy/h and 43 ± 2.15 nGy/h for maize and beans respectively which were lower than the admissible dose standard of 1500 nGy/h. The average annual effective ingestion dose (AEID) in maize and beans were 1.240 mSv/y and 0.263 mSv/y respectively. The average AEID values in maize were above the limit of 1mSv/y for the general public, as the International Commission on Radiological Protection (ICRP) recommended. This shows that there is an increased health risk for the whole body of an individual due to the intake of maize with higher AEID. While the AEID in maize suggests an elevated health risk for consumers due to whole-body radiation exposure, the overall radiological risk posed by beans and other consumption in the region remains minimal and within international safety limits hence poses no significant risk to the consumers and the general populace of Bungoma County.