HEAVY METALS LEVELS IN SOME FISH SPECIES HARVESTED FROM RIVER KADUNA, NIGERIA

Abstract

 In Nigeria, waste discharges from domestic, municipal, trade, industrial and agricultural set-ups contain various

pollutants including heavy metals which are conveyed (mostly untreated) through drains, water-ways and soils

into inland water-bodies. Fish, being relatively situated at the top of the aquatic food chain, normally accumulate

heavy metals from water, food and sediments and pass same along the food chain. This study was conducted to

determine the levels of some heavy metals including cadmium (Cd), lead (Pb), chromium (Cr) and zinc (Zn) in

fresh water fish samples obtained from River Kaduna, Nigeria. Five of the most common fish species were studied

on alternate months for the period of twelve months, giving a total of fifty seven fish samples examined for the

elemental toxicants. Digestion of the fish was in accordance with standard methods and determination of the

elements in the fish samples was carried out by means of an Atomic Absorption Spectrophotometry (Varian,

model AA240FS). All the fish samples tested contained the metals in varying concentrations. The metal

concentrations in the fish species were in the order Zn˃Cr˃Pb˃Cd. However, the levels of the metals in the fish

 species studied were within the permissible limits set by Food and Agriculture Organization. Based on this finding,

these species of fish from the river could be adjudged safe for human consumption. Continuous monitoring of fish

in River Kaduna is however recommended to ensure the heavy metals concentrations in the fish do not exceed the

recommended guideline values.