Toxic metal pollution and associated ecological and human health risks in soils and stream sediments of Idanre area, Southwest Nigeria

Toxic metals are persistent environmental pollutants with significant ecological and health risks due to their non-biodegradability and bioaccumulation. This study assessed the extent of toxic metal pollution and associated ecological and human health risks in soils and stream sediments of Idanre area, Southwest Nigeria. Forty samples (20 soils, 20 sediments) were analyzed using X-ray fluorescence for major oxides and trace metals. Multivariate statistical methods and geochemical indices were used to determine contamination levels and sources. Human health risks were evaluated using United States Environmental Protection Agency (USEPA) models for ingestion, inhalation, and dermal exposure. Results showed SiO₂ dominance in soils and sediments, indicating silicate-rich parent material. Elevated concentrations of Pb (24.59-82.19 mg/kg), Cd (0.63-1.96 mg/kg), and Cr (30-93.35 mg/kg) exceeded background levels, pointing to anthropogenic sources. Stream sediments showed higher contamination, especially Zn (avg. CF = 7.59), Cd (3.89), and Pb (3.98). Igeo values confirmed moderate to strong enrichment, and Cd posed moderate to high ecological risk (Er = 71.82-174.55). Health risk assessments indicated significant non-carcinogenic risks in children (HI = 4.88-9.66), mainly <i>via</i> dermal exposure and ingestion, with Pb, Cr, and Co as key contributors. Adults showed negligible risk, and carcinogenic risks remained within acceptable limits, with Cr as the main carcinogen.