of metal interactions with subcellular biochemical systems usually either are metabolites of the system affected (porphyrinurias) or represent some specific function of a cellular system being impaired (proteinurias). One typically finds a continuum of symptoms, from the subtle or so-called "no effect" bio chemical and physiological indicators of exposure to severe clinical disease and death. This continuum is the basis of much of the controversy since many health officials follow the traditional practice of applying the "threshold health-effect" concept in evaluating the problems of environmental exposure to metals. The past decade or so, however, has seen a vast increase in our understanding of the effects of elevated concentrations of toxic metals in local populations and ecosystems. At the same time, there is a growing awareness that the effects of the metals which occur naturally in the environment must be distinguished from those imposed by the pollutant fraction. This point was amply document ed in a recent study of cadmium intake and cadmium in a number of human tissues in Sweden, Japan, and the United States, which showed fairly conclu sively that the background exposure in Japan was about threefold higher than in the other two countries (2). One immediate implication is that any health ef fect studies of cadmium in Japan using control groups within that country are liable to underestimate the difference between the exposed and the control groups simply because of the the high "background" intake.

Inhalt
Historical Records of Metal Pollution in the Environment.- Anthropogenic Perturbation of Metal Fluxes into the Atmosphere.- Fluxes of Metals Through the Atmosphere and Oceans.- Metal Pollution of Terrestrial Waters.- Pollution of Soils by Cadmium.- The Contamination of Plants and Soils with Heavy Metals and the Transport of Metals in Terrestrial Food Chains.- Transport of Trace Metals in Marine Food Chains.- Additional Exposure Routes.- Bioavailability of Trace Elements in Foodstuffs and Beverages.- Bacterial Transformations of and Resistance to Heavy Metals.- New Approaches to Study Effects of Metals and Their Compounds in Vitro and in Vivo.- Biochemical Interactions of Mercury, Cadmium, and Lead.- Structural Aspects of Metal Toxicity.- Metabolism and Toxicity of Metals.- Cadmium.- Mercury.- The Hazard to Health of Lead Exposure at Low Dose.- Standard Setting and Metal Speciation: Arsenic.- Modeling Exposure Routes of Trace Metals from Sources to Man.- Changing Biogeochemical Cycles.- Routes of Exposure to Humans and Bioavailability.- Structure, Mechanism, and Toxicity.- Perspectives and Prospectives on Health Effects of Metals.- List of Participants.- Author Index.