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Review of heavy metals in the African aquatic environment.

Data were compiled from selected heavy metal studies in both freshwater and marine ecosystems from the major African subregions, Northern, West and Central, Eastern, and Southern Africa. The concentrations of heavy metals were compared between different environmental compartments (water, sediments, fauna, and flora), between the different African subregions and with data from other areas in the world. Despite the scarcity of the existing information on Africa, some conclusions could be drawn: Metal concentrations in organisms were generally below WHO limits except for some localized sites, mostly with increased lead levels. There were no significant differences between inland water and coastal animals, but shellfish had higher concentrations of most metals than finfish. For aquatic plants the heavy metal levels were higher in inland waters. Compared to more industrialized regions and with the exception of some hot-spot sites, the concentrations of heavy metals in African aquatic systems were low and close to natural background levels. Nevertheless, in view of the expected increase in urbanization and socio-economic activities in Africa, sources and quantities of heavy metal discharges to aquatic environments have to be identified. Also, pollution control measures should be formulated in each country.