ABSTRACT
The heavy metals can be divided into nonessential elements, such as lead, mercury, and probably cadmium and essential elements with relatively well-defined roles and functions. The potential risks to human health have prompted many investigations with respect to the more toxic metals cadmium, lead, and mercury. Of these metals, lead and mercury are thought to show the highest values for the ratio anthropogenic/natural input and are likely to pose the most serious pollution threat. Account should be taken of the limitations of data reported on metal levels in marine vertebrates. The marine vertebrates are for convenience, treated in the following subgroups: marine fish, both Chondrichthyes and Osteichthyes; seabirds, excluding sea ducks and divers; marine mammals. The limitations of comparing metal levels in different species with distinct geographical distributions should be taken into account, as should the potential bias of using dead seabirds and beached and stranded marine mammals for metal analysis.
