This program will focus on the most common chemical contaminants which results, or have resulted from mining of gold and silver in the desert environment of the Western United States. The program consists of six projects. In two of these projects cyanide (CN) will be studied because this toxic chemical is the most common chemical used today for the extraction of low-grade ores. Historically, gold and silver were commonly extracted using a mercury (Hg) amalgamation process which released large amounts of mercury into the environment. Six of the projects will study various aspects of Hg contamination/biomedical effects and will focus on one site, the Carson River Superfund Site (CRSS) in Northern Nevada. In this arid environment, selenium (Se) is naturally present in high concentration, and its intervention with Hg will also be investigated, especially as it relates to reproductive effects. The program includes 3 laboratory animal study (Hg); an ecology project (Hg/Se); a hydrogeology project (Hg); an atmospheric transport project (Hg); and an environmental chemistry project (CN). The latter 3 projects provide essential site and chemical characterization information to the biomedical projects. Considerable emphasis is placed on avian species, in addition to mammalian toxicity and human health effects, because migratory birds in this area are adversely affected by both CN and Hg waste. Two of the biomedical projects are intimately linked by a focus on oxidant-induced cellular damage, since both Hg and Cn damage mitochondria and may increase formation of reactive oxygen species. It is expected that the information obtained in this program will help to determine the threat to human health and ecological systems, particularly birds, from toxic mining waste. Furthermore, the geological and atmospheric transport studies will provide unique, predictive models which will be invaluable in assessing remedial action at the Carson River Site and will advance our basic understanding of the processes by which these toxins spread through our environment.