Concentration of heavy metals in selected edible fish species along the coast of Dar es Salaam

The concentrations of zinc, copper, cadmium and lead in fish were determined to asses the health hazards they constitute to fish consumers. Fish species were collected from local fishermen at four landing sites along the coast of Dar es Salaam from May to July 2002. Samples were analysed using atomic absorption spectrophotometer. The results show that heavy metal concentrations vary among organs within and between fish species. The highest metal concentrations were found in the liver, followed by kidney, gills and muscles. Mean concentrations of zinc (|jg g-1 dry wt.) in liver, kidneys, gills and muscles were 121.78, 72.87, 61.66 and 10.30 and 14.13, 8.36, 3.40 and 1.98 for copper respectively. Cadmium and lead were below the detection limit in muscles but for liver, kidney and gills, the mean values were 0.14, 0.10 and 0.01 pg g_1 for cadmium and 0.03, 0.04 and 0.06 [ig g-1 for lead respectively. There was significant difference in metal concentrations in tissues between fish species. When the results from this study were compared with those from other geographical regions of the world, they showed that Dar es Salaam coastal waters are not polluted. In general, the concentrations of zinc, copper, cadmium and lead in the muscles of the five fish species were within the permissible levels set for human consumption.