Investigation of Selenium and Iodine Status in Soils, Water, and Human Populations of Selected Communities in Kebbi State: A Geochemical and Nutritional Chemistry Perspective

Selenium and iodine deficiencies in soils and water translate directly into nutritional inadequacies in dependent populations, with documented health consequences including thyroid disorders, impaired immunity, and reproductive complications. This study investigates selenium and iodine concentrations in soils, drinking water, locally produced food crops, and urine samples from residents of four communities in Kebbi State, North West Nigeria, integrating geochemical and nutritional chemistry perspectives. Soil samples were collected at 0 to 20 and 20 to 40 centimetre depths. Drinking water was sampled from boreholes and surface sources. Staple food crops including millet, sorghum, and cowpea were collected at harvest. Spot urine samples were obtained from 80 adult and 40 child participants. Selenium was determined by hydride generation atomic fluorescence spectrometry, and iodine by the Sandell-Kolthoff kinetic colorimetric method. Geochemical maps of selenium and iodine distribution were produced using GIS interpolation. Results reveal that soil selenium concentrations are below the deficiency threshold of 100 micrograms per kilogram in three of four communities, associated with siliceous, weathered basement rocks. Urinary iodine concentrations in children indicate moderate iodine deficiency in two communities without access to iodised salt. Correlations between soil selenium and crop selenium concentrations confirm the geogenic pathway. The study recommends geochemical-guided targeting of selenium biofortification programmes and strengthened monitoring of iodised salt coverage in Northwest Nigeria. Keywords: selenium, iodine, Kebbi State, geochemistry, nutritional deficiency