Age-Dependent Radiological Risk and Organ Dosimetry from Consumption of Staple Crops in The Sokoto Basin, Nigeria

The study examined radionuclide concentrations, soil-to-crop transfer factors and age-specific organ doses from the consumption of maize, beans and pepper in the Sokoto Basin, North-West Nigeria. Activity concentrations of 226Ra, 232Th and 40K were determined by gamma-ray spectrometry in a total of 24 soil and 26 crop samples from eight Local Government Areas. The most significant finding was anomalous thorium transfer factors, near unity and 10–100 times larger than IAEA reference values, challenging the established paradigm of thorium immobility in agricultural systems. Infants showed the highest age-dependent committed effective doses, with doses 3.7-4.0 times the ICRP public limit of 1,000 µSv/yr, and excess lifetime cancer risk values were 236-2,347 times greater than UNSCEAR benchmarks. The highest organ-specific dose rates were recorded in the testes, bone marrow and lungs. The mean ingestion doses from maize consumption were significantly higher than the ICRP limits (48-52 %). These results demonstrated that the high transfer of thorium in calcareous semi-arid soils, combined with high maize consumption, pose significant risks of dietary exposure for the most vulnerable populations, emphasising the necessity for site-specific, age-segregated radiological assessment rather than generic international values.