per year from designated industrial and other sources. The air toxic provisions represented a major expansion in the number of air pollutant species of regulatory concern. Emissions from fossil-fueled power plants, however, were exempted from the provision of the amendments, pending further study by EPA. Extensive efforts currently are under way to characterize trace species emissions from coal-fired power plants as a basis for federal decisionmaking expected in late 1995 or soon thereafter. Air toxics concerns for utilities center primarily around 10 to 20 trace substances commonly found in coal, including arsenic, mercury, selenium, nickel, cadmium, and other heavy metals. The basis for regulating these species under the air toxics provisions would be a finding by EPA of an unacceptable health risk or an ecological risk to one or more regions of the country named in the 1990 CAAAs (Zeugin, 1992).
Individual states, however, could regulate on other grounds. Some states such as Wisconsin already are considering trace emission limitations for coal-burning plants based on trace substance concentrations in coal.1 The Electric Power Research Institute has compiled an extensive database of published information on trace substances, including extensive characterizations of U.S. coals. The data for bituminous, subbituminous, and lignite coals show large variability, often an order of magnitude or more, in trace species concentrations (Rubin et al., 1993). Detailed trace species data at the mine and seam levels, however, are not generally available, though a number of U.S. coal companies do possess proprietary information of that type. EPRI and DOE currently are conducting extensive testing programs to characterize trace species emissions from conventional and advanced power plants.
Of all the environmental issues facing the future use of coal, none is as potentially far reaching as the worldwide concern over global climate change. For coal, emissions of carbon dioxide (CO2) from combustion and methane from coal mining are the two greenhouse gases of primary concern. While it is likely to be at least a decade or more before the magnitude and consequences of global warming can be measured or predicted with reasonable scientific certainty, international concern over the potential effects of global warming has prompted recommendations and policy measures to curtail the growth in greenhouse gas emissions, primarily CO2 (e.g., NRC, 1992). As a result of the 1992 United Nations Conference on the Environment, the United States is signatory to an international accord to limit CO2 emissions to 1990 levels by the turn of the century. Recently, the Clinton administration put forth a program of largely voluntary measures to achieve that objective (Clinton and Gore, 1993).