	Introduction

Attention to environmental issues in the 110 th Congress focused early and heavily on climate change. Hearings were held by at least 10 committees, and 17 bills to cap emissions of greenhouse gases (GHGs) were introduced. One of the bills, S. 2191 , was reported, May 20, 2008, by the Environment and Public Works Committee, and Senate debate on a modified version ( S. 3036 ) began June 2, 2008. A motion to invoke cloture failed June 6, on a vote of 48-36. Whether or not climate change legislation would amend the Clean Air Act, climate change hearings and markup were among the highest priorities for the committees that have jurisdiction over air issues (principally the Senate Environment and Public Works and House Energy and Commerce Committees). Other clean air issues were not the main focus of attention, but they were addressed, primarily through oversight of Administration actions. And it might affect whether states have authority independent of the federal government to control certain greenhouse gas emissions. A U.S. cap-and-trade system for GHG emissions would face a number of challenges. No federal standards address greenhouse gas emissions from mobile sources, so the requirement that the state's standards be at least as protective as federal standards would appear to be met. Nevertheless, the EPA Administrator announced on December 19, 2007, that he would deny the waiver request. On February 29, 2008, the Administrator signed a formal decision document denying the waiver. Following the Administrator's decision, legislation was introduced in both the Senate ( S. 2555 ) and the House ( H.R. 5560 ) to overturn the Administrator's denial. The Senate bill was reported, June 27 ( S.Rept. 110-407 ), but no further action was taken. The Court's decision left EPA three options: (a) make a finding that motor vehicle GHG emissions may endanger public health or welfare, and issue emissions standards; (b) make a finding that such emissions do not endanger public health or welfare; or (c) decide that climate change science is so uncertain as to preclude making a finding either way (or cite some other "reasonable explanation" why EPA will not exercise its discretion either way). With this background in mind, the remainder of this report provides a discussion of several interrelated air issues of interest in the 110 th Congress, including revision of the ozone, particulate, and lead standards, the role of independent scientific review in the setting of air quality standards, multi-pollutant legislation and the Clean Air Interstate Rule (CAIR) for electric power plants, mercury from power plants, and New Source Review. Challenged in the D.C. The centerpiece of the Bush Administration's approach to regulating power plants has been the Clean Air Interstate Rule (CAIR), a cap-and-trade regulation designed to reduce emissions of sulfur dioxide and nitrogen oxides, reducing the downwind effects of these pollutants on attainment of the ozone and PM 2.5 air quality standards. Circuit July 11, 2008, in North Carolina v. EPA , dealing a serious setback to the Administration's approach to controlling power plant pollution. On February 8, 2008, the U.S. Court of Appeals for the D.C. Circuit vacated these regulations as well and remanded them to EPA for reconsideration. Next Steps

Under the D.C. Circuit Rejects EPA ' s Mercury Rules: New Jersey v. EPA , by [author name scrubbed] and [author name scrubbed].) On April 2, 2007, the Supreme Court overturned the lower court rulings in a unanimous decision, finding that EPA's regulations, promulgated in 1980, clearly specified an increase in actual annual emissions as the measure of whether a permit for a modification was required.
Attention to environmental issues in the 110th Congress focused early and heavily on climate change—the state of the science, and whether (and, if so, how) to address greenhouse gas (GHG) emissions. Seventeen bills were introduced to establish GHG emission caps, and hearings on climate change were held by at least 10 committees. The Lieberman-Warner bill to establish a cap-and-trade system for GHG emissions (S. 2191) was reported by the Senate Environment and Public Works Committee, May 20, 2008. Senate debate began on a modified version of the bill (S. 3036) June 2 but ended June 6, as the Senate failed to muster sufficient votes to invoke cloture.
Climate change hearings and markup were among the highest priorities for the committees that have jurisdiction over air issues (principally Senate Environment and Public Works and House Energy and Commerce). Other clean air issues were addressed largely through oversight of Administration actions. Oversight issues included how best to control emissions of mercury and other pollutants from electric power plants; whether EPA's new standards for ambient air concentrations of fine particulates, ozone, and lead adequately reflect the state of the science; and whether EPA's new process for setting ambient air quality standards politicized what traditionally have been scientific judgments.
In addition to EPA, state governments and the courts have taken action on air issues that has stirred congressional interest. On April 2, 2007, the Supreme Court decided Massachusetts v. EPA, finding that EPA has authority under the Clean Air Act to regulate greenhouse gas emissions from new motor vehicles and requiring EPA to make a finding as to whether such emissions endanger public health or welfare. On February 8, 2008, the D.C. Circuit Court of Appeals, in New Jersey v. EPA, found EPA's approach to the regulation of power plant mercury emissions to be unlawful. On July 11, 2008, in North Carolina v. EPA, the D.C. Circuit vacated the Clean Air Interstate Rule (CAIR), which would have controlled emissions from power plants affecting air quality in downwind states. Other cases involving climate change, clean air standards, and the regulation of power plants are pending at the D.C. Circuit Court of Appeals and in a number of federal and state courts. Decisions in these cases may prompt hearings or legislation.
States interested in setting more stringent environmental standards are continuing to develop and implement regulations that go well beyond the requirements of federal law. Of particular interest is California's request for a waiver of federal preemption to control greenhouse gas emissions from cars and light trucks. On December 19, 2007, EPA announced that it would deny the waiver request, and the agency's Administrator signed a decision document formalizing his denial, February 29, 2008. California and more than a dozen other states are challenging the denial in court. Legislation was introduced in both the Senate (S. 2555) and the House (H.R. 5560) to overturn the Administrator's decision. The Senate bill was reported June 27, 2008, but no further action was taken.