Potential Health Risk Assessment of Bioaccumulation of Heavy Metals in Freshwater Organisms from Ojo River, Lagos, Nigeria

Abstract

This study investigated potential health risk associated with heavy metal bioaccumulation in freshwater organisms in Ojo River, Lagos, Nigeria. Liver, gills and muscle from fish samples and muscle and exoskeleton from crab samples were analysed for concentration of Cd, Cr, Zn, Pb, Ni and Cu using Atomic Absorption Spectrophotometer after digestion of samples. Generally, heavy metal concentration in water samples from different locations in Ojo River did not exceed WHO limits. Concentration of Pb, Cu, Zn and Cr in tissues of M. niger and L. campechanus shows high bioaccumulation of heavy metals. Heavy metals bioaccumulated more in liver > muscle > gills in both fish samples. Ni and Cd were not detected in the two fish species. Similarly, Pb, Cu and Ni were found in muscles and exoskeleton of C. pagurus and S. serrate at quantities higher than WHO limits. Zinc was detected only in muscle and not exoskeleton of both crab samples, while Cr was found only in exoskeleton of C. pagurus and Ni was not detected in all crab species. Estimated daily intake (EDIs) for Pb, Cu, Zn and Cr in M. niger and L. campechanus and for Pb, Cu and Ni in C. pagurus and S. serrate were higher than the oral reference doses. Target Hazard Quotient (THQ) for heavy metals were also extremely high. Significantly high bioaccumulation of heavy metals in freshwater organisms from Ojo River calls for serious actions because it is a major source of freshwater foods for residents of Lagos.