Geochemical distribution, pollution evaluation, and radiological health hazards of naturally occurring radionuclides in soil and stream sediments from Idanre area, Southwest Nigeria

This study investigates the geochemical distribution, pollution levels, and radiological health risks of naturally occurring radionuclides (²³⁸U, ²³²Th, and ⁴⁰K) in soils and stream sediments from the Idanre area, Southwest Nigeria. Forty samples (20 soils and 20 stream sediments) were analyzed using X-Ray fluorescence (XRF). Activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in soils averaged 73.29 Bq/kg, 44.03 Bq/kg, and 1614.65 Bq/kg, respectively, while stream sediments showed higher averages for ²³⁸U (103.03 Bq/kg) and ⁴⁰K (1421.23 Bq/kg). These values exceeded global averages, indicating elevated natural radioactivity in the region. Pollution indices, including geo-accumulation (Igeo), contamination factor (CF), and pollution load index (PLI), revealed moderate to high contamination levels for ²³⁸U and ⁴⁰K, with 232Th showing lower contamination. Radiological hazard indices, such as the internal hazard index (Hint) and external hazard index (Hext), exceeded safety thresholds, highlighting potential health risks, particularly from radon exposure. The annual effective dose equivalent (AEDE) and excess lifetime cancer risk (ELCR) were above global averages, with higher risks observed in indoor environments due to limited ventilation. In this study, spatial analysis identified localized hotspots in the northeastern, northwestern, and southeastern regions. The study underscores the need for monitoring and mitigation measures to reduce radiological risks in the area. Future research should expand to include other environmental media, implement long-term monitoring, and conduct epidemiological studies to assess actual health impacts on the local population.