	Part One: Introduction

On December 15, 2009, the Environmental Protection Agency (EPA) published its most important action to date related to climate change. It found that the combined greenhouse gas (GHG) emissions from new motor vehicles in the United States contribute to an "endangerment" from climate change. More precisely, EPA found that such emissions, in the words of Clean Air Act (CAA) section 202(a), "cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare." Under section 202(a), this final determination requires that EPA promulgate "standards" to control such emissions from new motor vehicles. Rather, objection has been raised to the section 202 endangerment finding for GHGs and the upcoming motor vehicle GHG emission standards because of the argument they will trigger a cascade of unacceptable regulatory consequences under other CAA provisions. These regulatory consequences, objectors say, would impose unattainable air quality goals on EPA and the states, and/or economically and administratively unreasonable burdens on both EPA and regulated entities. This report examines the CAA provisions that have figured in this debate to assess whether this alleged "cascade" of legal consequences would likely occur as the result of EPA's endangerment finding under 202(a) and resulting emission standards. A caveat: the issue analyzed here is important primarily if Congress does not enact climate change legislation that puts regulation of emissions based on their climate change impacts beyond the reach of some of the CAA provisions discussed here. In particular, the House-passed climate change bill, H.R. 2454 , states that sections 108 (national ambient air quality standards) and 115 (international air pollution) may not be used to address air pollutants based on their climate change impacts. The bill also would prohibit the use of section 165 (requiring preconstruction "new source review" in Prevention of Significant Deterioration areas) to regulate GHG emissions, and specifies that no stationary source of GHGs could be required to obtain a permit under Title V of the CAA solely because of its GHG emissions. Actually, EPA's endangerment determination consists of two findings, one addressing each component of the section 202(a) endangerment provision. Part Three: CAA Sections with Endangerment Triggers Other Than Section 202(a)

To what extent will the endangerment finding under section 202(a) narrow EPA's discretion to deal, or not deal, with GHGs under other CAA provisions with endangerment preconditions? This is an important preliminary step in understanding the legal relevance of EPA's 202(a) endangerment finding to other endangerment-triggered sections of the CAA—but it is only a preliminary step. Pollution in a Foreign Country Caused by Emission Sources in the United States

Under CAA section 115, "[w]henever the [EPA] Administrator, upon receipt of reports … from any duly constituted international agency has reason to believe that any air pollutant or pollutants emitted in the United States cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare in a foreign country ," it must notify the governors of the states where the emission originates. In short, what event triggers the requirement of best available control technology (BACT) in PSD areas? EPA asserts in the preamble to the proposed tailoring rule that adherence to the 100/250 tons/year threshold for new source review in PSD areas would have precisely this result:
the extraordinary increases in PSD and Title V permit applications that would result from a literal application of the 100/250 tpy threshold requirements would, at least during the near term—until EPA and the permitting authorities can develop streamlining methods and ramp up resources—extensively disrupt the two permitting programs and impose undue regulatory burdens in the aggregate on the sources newly subject to PSD and Title V permit requirements. Title V permitting requirements likely will be triggered as well. Stationary source categories that do not emit large amounts of GHGs will not have to be covered by NSPSs if EPA defines "significantly" at a high tons/year level.
On December 15, 2009, the Environmental Protection Agency (EPA) took its most important action to date related to climate change. EPA published its final determination that the combined greenhouse gas (GHG) emissions from new motor vehicles in the United States contribute to an "endangerment" from climate change. More precisely, EPA found that such emissions, in the words of Clean Air Act (CAA) section 202(a), "cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare." Under section 202(a), this finding requires that EPA promulgate "standards" to control such emissions—as the agency proposed to do for light-duty motor vehicles in advance of its endangerment determination.
Some groups have objected to the endangerment determination and the emission standards to follow, arguing they will trigger a "cascade" of unacceptable regulatory consequences under other CAA provisions. These regulatory consequences, they say, would impose unattainable GHG-concentration goals on EPA and the states, and/or economically and administratively unreasonable burdens. This report examines the CAA provisions that have figured in this debate to see whether this alleged cascade of legal consequences likely would occur.
First, the report examines CAA sections that, like section 202(a), are triggered by endangerment findings. Of these, the one most likely to require EPA regulatory action after the 202(a) endangerment finding is section 111, authorizing new source performance standards—but only as to stationary source categories emitting the largest amounts of GHGs. Section 111, however, affords EPA wide discretion in setting new source performance standards. Two other sections that arguably might be triggered are 108, requiring national ambient air quality standards, and 115, which requires states to revise their implementation plans to prevent or eliminate the endangerment of public health or welfare in a foreign country. As to these sections, however, the arguable infeasibility of the regulatory goals—even if GHG emissions in the United States are significantly reduced, atmospheric concentrations would decline little—will give EPA room to argue that regulatory action is not mandatory. Other endangerment-triggered sections of the CAA can be distinguished from section 202(a) by their explicit terms, and thus would likely not be triggered by the 202(a) endangerment finding.
Second, the report looks at CAA provisions having no endangerment trigger. Of these, EPA has conceded that two require the agency to act after it promulgates the required emission standards following the 202(a) endangerment finding. One provision would require EPA to impose "best available control technology" (BACT) on GHG emissions from any major emitting facility proposed to be constructed in a Prevention of Significant Deterioration area. The other, Title V, creates an operating permit program for stationary sources of emissions, and would require stationary sources subject to BACT under the first provision to also apply for Title V permits. As to each of these requirements, EPA has proposed a "tailoring rule" setting emission thresholds far higher than in the CAA, at least for a few years. EPA justifies the departure from statutory language under the case law doctrines of "absurd results" and "administrative necessity."
A caveat: the issue analyzed in this report is important primarily if Congress does not enact climate change legislation that puts regulation of GHGs beyond the reach of some of the CAA provisions discussed here. In particular, the House-passed climate change bill, H.R. 2454 (the American Clean Energy and Security Act of 2009), states that three of the CAA sections treated in this report, and one CAA title, may not be used to address air pollutants based on their climate change impacts.