ABSTRACT
A recent inventory of man-induced mobilization of heavy metals into the biosphere1 concluded that "mankind has become the most important element in the global biogeochemical cycling of the trace metals." All heavy metals, whether biologically essential or not, have the potential to be toxic to organisms at a threshold bioavailability. Toxic effects may be reflected at the individual, population, or ecosystem level, affecting species composition and production levels, or may be of direct dietary significance to man. Knowledge of the manner in which animals deal with potentially toxic concentrations of heavy metals is of fundamental importance in the assessment of metal pollution by analysis of metal levels in biological samples. Heavy metals are often referred to as trace metals, occurring as they do in low concentrations in organisms, although the term trace metal might imply the presence of an essential requirement by organisms for that metal.
