On Tuesday, Dec. 15, 2009, the U.S. Environmental Protection Agency (EPA) endangerment finding for greenhouse gases (GHGs) was published in the Federal Register. The endangerment finding concluded that six GHGs taken in combination endanger both public health and welfare. Additionally, the EPA concluded that the combined emissions of GHGs from new motor vehicles and motor vehicle engines contribute to GHG emissions which threaten public health and welfare.
The finding clears the way for the EPA to issue a rule establishing emissions standards for motor vehicles. The EPA expects to issue that rule in March 2010, and the rule will become effective 60 days later. Once effective, GHGs will become regulated pollutants under the Clean Air Act and subject to controls under the PSD/NSR preconstruction permitting programs when a new stationary source of emissions—such as a manufacturing facility or power plant—is constructed or when an existing source undergoes a major modification. Those sources would be required to install best available control technology to control GHG emissions if emitted above certain threshold amounts.
The six GHGs that are listed in the endangerment finding—carbon dioxide, methane, nitrous oxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride—are defined as "air pollution" and are noted to be long-lived and directly-emitted. The EPA noted that the findings are based on scientific research indicating the danger of GHGs to health and mortality, as well as the potential for climate disruption.
The EPA's decision was prompted by the 2007 Supreme Court decision in Massachusetts v. EPA, where the Supreme Court held that GHGs were "air pollutants" under the Clean Air Act. The Court held that in response to the petition to regulate GHGs for motor vehicles, the EPA was obligated to determine whether or not motor vehicles cause or contribute to air pollution which may be anticipated to endanger public health or welfare. In the December decision EPA found that motor vehicles make a meaningful contribution to climate change. While the finding of endangerment imposes no direct requirements at this time, it could lead to the promulgation of emission standards for motor vehicles and likely other industries, if the EPA concludes that those source categories also contribute to the GHG emissions.
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