The impact of mining and smelting of metal ores on environmental quality is described. Mines produce large amounts of waste because the ore is only a small fraction of the total volume of the mined material. In the metal industry, production of Cu, Pb, and Zn causes the greatest degradation of the environment. Copper mining produces extensive mine wastes and tailings and Cu smelting emits approximately 0.11 Mg of S per Mg of Cu produced in the USA. Zinc and Pb smelters release large quantities of Cd and Pb into the environment. Metal smelting and refining produce gaseous (CO2, SO2, NOx, etc.) and particulate matter emissions, sewage waters, and solid wastes. Soil contamination with trace metals is considered a serious problem related to smelting; however, mining and smelting are not main sources of global metal input into soils. Other sources like discarded manufactured products, coal ash, agriculture, and transportation take a lead. Smelters are the main sources of atmospheric emissions of As, Cu, Cd, Sb, and Zn on a global scale and they contribute substantially to the overall emissions of Cr, Pb, Se, and Ni. A quantitative evaluation of the environmental health effects of mining and smelting is difficult because of the complexity of factors involved and lack of consistent methodology. Nevertheless, the case studies described indicate that negative health effects could arise from Pb mining and smelting. Risk assessment revealed that food chain contamination by Cd from soils contaminated by smelting is very unlikely under the western diet.

Contaminated soils can be a source for crop plants of such elements like As, Cd, Cr, Cu, Ni, Pb, and Zn. The excessive transfer of As, Cu, Ni, and Zn to the food chain is controlled by a "soil-plant barrier"; however, for some elements, including Cd, the soil-plant barrier fails. The level of Cd ingested by average person in USA is about 12 micrograms/day, which is relatively low comparing to Risk Reference Dose (70 micrograms Cd/day) established by USEPA. Food of plant origin is a main source of Cd intake by modern society. Fish and shellfish may be a dominant dietary sources of Hg for some human populations. About half of human Pb intake is through food, of which more than half originates from plants. Dietary intake of Cd and Pb may be increased by application of sludges on cropland with already high levels of these metals. Soils amended with sludges in the USA will be permitted (by USEPA-503 regulations) to accumulate Cr, Cd, Cu, Pb, Hg, Ni, and Se, and Zn to levels from 10 to 100 times the present baseline concentrations. These levels are very permissive by international standards. Because of the limited supply of toxicity data obtained from metals applied in sewage sludge, predictions as to the new regulations will protect crop plants from metal toxicities, and food chain from contamination, are difficult to make.

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