Organochlorine Pesticide Residues and Associated Health Risks in Fish From Osun River, Southwestern Nigeria

This study investigated the occurrence, spatial-seasonal distribution, and potential human health risks of organochlorine pesticide (OCP) residues in fish collected from eight locations along the Osun River, southwestern Nigeria. Seventeen OCP congeners, including γ-BHC, DDT and its metabolites (DDE and DDD), dieldrin, and heptachlor epoxide, were analyzed using gas chromatography equipped with an electron capture detector (GC-ECD). Descriptive and inferential statistics were employed, whereas human health risks were assessed using carcinogenic and noncarcinogenic indices. Total OCP concentrations in fish ranged from 0.219 to 2.555 mg/kg, with γ-BHC recording the highest concentration (0.994 mg/kg), exceeding the FAO/WHO permissible limit of 0.2 mg/kg. Hazard Index values exceeded the recommended safety threshold (HI > 1) at Oke Gada (1.315), Tesan (1.273), and Odo Oba (1.133), indicating possible health risks to fish consumers. Principal component analysis identified patterns among OCP congeners that may be consistent with historical pesticide application, environmental transformation processes, sediment-associated contamination, and other potential environmental inputs. Carcinogenic risk values exceeded the acceptable USEPA limit (1 × 10^-4) at seven of the eight sampling sites, with the highest value observed at Tesan (1.27 × 10^-3). Among the detected compounds, γ-BHC and heptachlor epoxide contributed most significantly to both carcinogenic and noncarcinogenic risks. The findings indicate that OCP contamination was present in fish from the Osun River during the study period and highlight the importance of continued environmental monitoring, effective pesticide management, and sustainable pest control practices to reduce potential exposure risks.