ASSESSMENT OF POTENTIALLY TOXIC HEAVY METALS AND HUMAN HEALTH RISK IN WATER, SEDIMENTS AND TISSUES OF MOON FISH Citharinus citharus FROM THE AXIS OF LOWER RIVER NIGER AT OGURO AJAOKUTA NIGERIA

Abstract

This study determined bio concentration of heavy metals in water, sediment, and tissues (gill, viscera and muscle) of Citharinus citharus from the axis lower River Niger at Oguro, Ajaokuta, Nigeria, and also assessed potential human health risks from consuming water and fish therein. Water, sediment, and fish samples were collected from three designated sites along the river twice per month for three months June, July and August (rainy season). The samples were analyzed using Atomic Absorption Spectrophotometry (AAS) for heavy metals which includes iron (Fe), lead (Pb), nickel (Ni), chromium (Cr), cadmium (Cd), and zinc (Zn). The findings show that Fe concentrations in water peaked at 11.679 mg/kg in July, exceeding the WHO guideline of 0.300 mg/kg, while Pb and Ni concentrations surpassed WHO limits at all sites across the three months. Sediment analysis revealed that Fe ranged from 168.282 mg/kg to 244.800 mg/kg, with Cd peaking at 0.841 mg/kg in July. In fish tissues, Fe concentrations were highest in gills (51.121 mg/kg), followed by viscera (48.403 mg/kg), and muscle (34.921 mg/kg). The Estimated Daily Intake (EDI) for zinc in gills reached 2.99 × 10⁻² mg/kg/day, while the Target Hazard Quotient (THQ) for Cr in gills was 0.127, signaling a moderate health risk. The study concludes that heavy metal contamination in the Lower River Niger poses no significant ecological and human health risks, particularly during the study period . It recommends stricter regulation of industrial discharge, public health campaigns on fish consumption, and continuous environmental monitoring to mitigate the long-term impacts of heavy metal pollution