ASSESSMENT OF POLLUTION AND HUMAN HEALTH RISK OF WATER AND SEDIMENT OF IGBOKODA MARKET BEACH SECTION OF OLUWA RIVER, ONDO STATE, NIGERIA.

Water is a vital resource for human, agricultural, and industrial needs, but pollution poses serious risks to ecosystems and public health, especially in communities dependent on surface water. This study aim to assess the pollution load and human health risks of water and sediment of Igbokoda Market Beach Section of Oluwa River in Ondo State. Water and sediment samples were collected aseptically and processed for microbiological analyses by conventional microbiological methods. The physicochemical and heavy metal analyses were determined by physical and chemical analytical techniques. Bacteriological analysis revealed high microbial loads, with Total Heterotrophic Bacteria (THB) counts of 4.35 × 10⁸ (CFU/mL) in water and 4.3 × 10⁸ (CFU/mL) in sediment. Presumptive coliform counts exceeded 1100 MPN/100mL in water and 75 MPN/100mL in sediment, with Escherichia coli present in both samples. Physicochemical parameters showed pH within permissible limits, while turbidity (16.73 NTU), BOD (16.84 mg/L), COD (13.61 mg/L), and phosphate (0.52 mg/L in water) exceeded standards. Sediment showed high cation exchange capacity (11.58 Cmolc/kg) and organic matter (2.71%). Heavy metal analysis showed Fe, Cd, Pb, Cr, Ni, and As in water were above WHO limits, while sediment metals were largely within permissible levels. The water quality index of the river was 648.45 above WHO guidelines for drinking water and CPI (3.75), whereas sediment indices (Contamination Factor, Geochemical accumulation, Pollution Load Index, Potential Ecological Risk Index) showed low to no pollution. Human health risk assessment of adult (HI= 4.54) and children (HI= 9.07) revealed ingestion as the major pathway, with children more vulnerable. Dermal health risk of adult (HI= 0.345) and children (0.86) were below the standard of HI < 1. In conclusion, the surface water and sediment of the Igbokoda Market Beach section of Oluwa River poses substantial environmental and lifethreatening public health concerns.