plete, due to information withheld for proprietary reasons. Thus, in a number of cases, we have been forced to work back from smelting or concentration process data to estimate the input quantities of concentrates. Our summary was given in Table 3. It excluded ferroalloys, of which U.S. production was about 1 MMT, because of the extreme complexity of the subsector.

Inputs to the U.S. primary metals sector consist of concentrates (either produced in the mining sector or imported), fuels, fluxes, and processing chemicals. Because we have accounted for inputs to and wastes from fossil fuel combustion in an above section, those quantities are not included in our accounting of wastes from primary metals smelting and refining. CO is a major pollutant of smelting processes, but it results from partial oxidation, which is later completed in the atmosphere. (Thus, the materials-balance approach is not applicable for estimating CO emissions.) Major purchased inputs, other than concentrates, are fluxes. The most important are limestone and dolomite. In 1988, approximately 9.6