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Heavy metals load in tilapia species: a case study of Jakara river and Kusalla dam, Kano state, Nigeria
Abstract
Between August and September 2009, twenty four (24) Tilapia species, twelve (12) from each site
were sampled from Jakara River and Kusalla dam in Kano, Nigeria with the view to determine the
level of some heavy metals in the muscles of the fishes so as to assess their safety or otherwise for
human consumption. The weight of each of the samples was determined using Gallenkamp
weighing balance and recorded to the nearest grams. The fishes were dissected to separate the
muscles from head, viscera and bones. Five grams of the muscle from each sample was digested
using concentrated nitric acid and hydrogen peroxide solutions prepared in the ratio of 1:1. The
digested samples were aspirated using 210 VGP Atomic Absorption Spectrophotometer from which
copper, zinc and lead were determined. The fish samples analysed from Jakara River had the mean
copper, zinc and lead concentrations of 0.46+0.14mg/kg, 15.83+5.05 mg/kg and 0.57+0.20mg/kg
and those from Kusalla dam had the means of 0.38+0.31mg/kg, 12.04+2.99 mg/kg and
0.54+0.29mg/kg respectively. Comparison of the above means with FAO standards for Cu
(30mg/kg), Zn (30mg/kg) and Pb (0.50mg/kg) revealed that the mean concentrations of copper
and zinc are safe for human consumption. However, the mean lead concentration exceeded the
limit prescribed for human consumption. This suggests the possible adverse health effect such as
damage to the gastrointestinal tract and chronic damage to the Central Nervous System among
others that the people consuming Tilapia species from both study sites could be exposed to. It was
recommended that considerable attention be paid to the lead content in fresh water fish at both
sites by appropriate authorities due to its possible health implication on the consumers.
Furthermore, continuous monitoring of heavy metals load in fish will be needed in Jakara River and
Kusalla dam. Similarly, measures should be put in place to control the inflow of raw effluent into
the river as they are largely the possible sources of these metals.
were sampled from Jakara River and Kusalla dam in Kano, Nigeria with the view to determine the
level of some heavy metals in the muscles of the fishes so as to assess their safety or otherwise for
human consumption. The weight of each of the samples was determined using Gallenkamp
weighing balance and recorded to the nearest grams. The fishes were dissected to separate the
muscles from head, viscera and bones. Five grams of the muscle from each sample was digested
using concentrated nitric acid and hydrogen peroxide solutions prepared in the ratio of 1:1. The
digested samples were aspirated using 210 VGP Atomic Absorption Spectrophotometer from which
copper, zinc and lead were determined. The fish samples analysed from Jakara River had the mean
copper, zinc and lead concentrations of 0.46+0.14mg/kg, 15.83+5.05 mg/kg and 0.57+0.20mg/kg
and those from Kusalla dam had the means of 0.38+0.31mg/kg, 12.04+2.99 mg/kg and
0.54+0.29mg/kg respectively. Comparison of the above means with FAO standards for Cu
(30mg/kg), Zn (30mg/kg) and Pb (0.50mg/kg) revealed that the mean concentrations of copper
and zinc are safe for human consumption. However, the mean lead concentration exceeded the
limit prescribed for human consumption. This suggests the possible adverse health effect such as
damage to the gastrointestinal tract and chronic damage to the Central Nervous System among
others that the people consuming Tilapia species from both study sites could be exposed to. It was
recommended that considerable attention be paid to the lead content in fresh water fish at both
sites by appropriate authorities due to its possible health implication on the consumers.
Furthermore, continuous monitoring of heavy metals load in fish will be needed in Jakara River and
Kusalla dam. Similarly, measures should be put in place to control the inflow of raw effluent into
the river as they are largely the possible sources of these metals.
