Pages: (10-18 )
Abstract
Cadmium and lead found naturally in the earth crust and from industrial discharge are capable of contaminating water bodies and aquatic organisms. Contaminated sea foods threaten human health because they pose negative impacts on consumption. The objective of this study was to assess the assimilation pattern of cadmium and lead in selected tissues of the African Catfish (Clarias gariepinus) that is commonly consumed in Nigeria.
Fish samples (36) were randomly distributed into 3 groups of 12 fish each. Group A was exposed to 4.9 mg/L cadmium, B to 24.2 mg/L lead for 4 weeks while group C served as control. Three fish samples were randomly selected from each group weekly. Each fish sample was sacrificed to isolate gills, liver and flesh. All samples were oven-dried, acid digested and analysed for cadmium and lead using atomic absorption spectrophotometer.
Cadmium concentrations in gills, liver and flesh of group A samples were 31.4±10.5 mg/kg, 38.3±11.6 mg/kg and 8.8±5.1 mg/kg respectively. For group B samples, lead concentration in gills, liver and flesh were 123.3±42.9 mg/kg, 82.6±29.1 mg/kg and 44.6±22.5 mg/kg respectively. Cadmium and lead were not detected in the gills, liver and flesh of fish samples in the control group C. This study observed cadmium and lead assimilation in the decreasing order of liver > gills > flesh and gills> liver> flesh respectively. There is a significant increase in cadmium and lead levels of gills and liver compared to flesh (p<0.05).
Gills and liver of Clarias gariepinus assimilated more cadmium and lead than the flesh. Thorough washing of fish and eviscerating the gills and liver before consumption will reduce the risk of exposure to cadmium and lead from the Clarias gariepinus.
Keywords: Heavy metals assimilation, bio-concentration, Clarias gariepinus, cadmium and lead,