With the world’s growing population, the provision of a safe, nutritious, and wholesome food supply
has become a major challenge. Owing to both manmade and natural processes, an array of chemical
and toxic agents find their way into our food supplies, including fish, through multiple routes. When
consumed, such contaminated food can endanger or even destroy life. This study was designed to
determine the level of four toxic heavy metals: lead, cadmium, mercury and arsenic, in edible muscles
of four fish species namely Tilapia nilotica (Tilapia), Synodontis guntheri (Kurungu), Heterotis niloticus (Bargi), and Clarias anguillaris (Catfish), harvested from three locations namely: Alua Dam, Doron
Baga and Dabamasara within the Lake Chad Basin of Borno State, Nigeria. The main objective was
to investigate the possible effects of seasons (dry and rainy) and smoking of the fish on the
concentration of the toxic heavy metals in the fish using acid digestion. The toxic heavy metals,
expressed in parts per million (ppm), were detected in all the fish species sampled during the dry and
rainy seasons from the three (3) in land waters investigated. The overall mean concentrations of the
heavy metals were significantly higher (P£0.05) in fresh fish samples harvested during the rainy
season than that of the dry season. Significantly different variations were also observed within fish
types and between locations in the concentrations of the four heavy metals. Smoking of the fish also
resulted in significant increases (P£0.05) of the metals, especially in lead and mercury concentrations
in smoked samples during the two seasons. Cadmium and arsenic were the lowest recorded metals in both fresh and smoked fish during the two seasons and from all the locations. Washing the smoked
samples with double distilled water resulted in significant reduction of more than 50% of the metals in
the smoked fish, indicating that the metals were mainly present in the smoked fish as surface
contaminants. The sequence of the heavy metals concentrations in all the fish samples was
Pb>Hg>Cd>As. Comparisons between the heavy metal contents of fish obtained in this study and the
range of metal concentrations from other foods were presented. The concentrations of the metals in
both the fresh and smoked samples from all the locations during the two seasons were however lower
than the internationally recommended threshold levels. Although continued surveillance for toxic
heavy metal contents in fish was recommended, this study however, concluded that fish from Lake
Chad basin are still safe for human consumption as far as their heavy metal contents is concerned.
Author (s) Details
Amin O. Igwegbe Department of Food Science and Technology, Faculty of Engineering Nigeria.
Afodia L. Kassum Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, P. M. B. 1069 Maiduguri, Nigeria.
Paul Y. Idakwo Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, P. M. B. 1069 Maiduguri, Nigeria.
Mamudu H. Badau Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, P. M. B. 1069 Maiduguri, Nigeria.
Amina I. Maijalo
Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, P. M. B. 1069 Maiduguri, Nigeria.