Ecotoxicology of Metals: Sources, Transport, and Effects on the Ecosystem

Metal-smelting and combustion processes are the major anthropogenic sources for the emission of metals to the atmosphere. Metals emitted this way are generally bound in small particles with the potential for atmospheric long-range transport and contamination. Sediments are the ultimate sink for metals emitted to the aquatic environment; this is most evident in coastal and estuarine sediments. Besides direct emissions, man-made environmental changes such as acidification, oxygen depletion, and draining of waterlogged areas may mobilize metals not otherwise available to organisms. The speciation of metals is an important determinant for their bioavailability, uptake, and toxicity in the environment. Organisms have developed a wide range of mechanisms for the internal handling and storage of essential and/or toxic metals. No metal other than mercury is consistently biomagnified along food chains. In the environment, the most adverse impacts of metals (on populations) have been caused by organic tin compounds used in antifouling paints and aluminum mobilized by acid rain. High concentrations of organic mercury and cadmium in certain organisms may cause concerns for the health of human populations that rely heavily on their use as food items.