HEAVY METAL EVALUATION: POTENTIAL RISK FOR HUMAN HEALTH AND IMPACT ON TISSUES OF TILAPIA FISH (OREOCHROMIS NILOTICUS) FROM A NATURAL URBAN RIVER

Abstract

This research study sought to determine the effect of some heavy metals on non-carcinogenic health risk for humans and tissues of Tilapia (Oreochromis niloticus) harvested from Dandaru River (a natural urban river) located South-West of Nigeria. Concentration of magnesium, nickel, manganese, cadmium, iron, zinc, copper, lead, and cobalt in water sample, gill, liver, intestine, and muscle of fish was quantified spectrophotometrically. Bioaccumulation factor (BAF) and hazard quotient (HQ) were estimated. Histopathological lesions in fish tissue were assessed. Heavy metals in water sample were mostly within permissible limits set by water quality regulatory agencies but, considerably high across target tissues. An appreciable number of the metals were bioaccumulative (BAF=1000-5000) or extremely bioaccumulative (BAF>5000) across all tissues. Hazard quotient were above the acceptable limit (>1.00) for most of the metals. The gills showed curling of secondary lamella, hyperplasia as well as oedema. Dilated sinusoids and congestive melanomacrophages were seen in the liver. Degeneration of intestinal mucosal surface was evident. Atrophy, inflammation and degeneration of smooth and skeletal muscle fibers were obvious. Conclusively, the combination of high hazard quotient and histological deformations seen in fish tissue confirms possible health risk to humans and adverse impact of heavy metals on fish.