On December 7, 2009, the US Environmental Protection Agency (the “Agency” or “EPA”) issued its “endangerment” findings under the Clean Air Act (CAA) for greenhouse gases (GHGs). Specifically, the Agency concluded that (i) the mix of carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride constitutes air pollution that reasonably may be anticipated to endanger public health and welfare, and (ii) the combined emissions of the aggregate group of those GHGs from new motor vehicles and engines contribute to that air pollution.

Under the CAA, the Agency now must proceed to set standards for emissions of those air pollutants. Toward that end, EPA already has proposed fleet-wide carbon dioxide emission levels for model-year 2012-2016 cars and trucks in conjunction with the National Highway Traffic Safety Administration’s (NHTSA’s) corporate average fuel economy standards. See 74 Fed. Reg. 49,454 (Sept. 28, 2009). There, EPA also proposed to cap nitrous oxide and methane tailpipe emissions.

But these findings have implications for stationary sources as well, including many buildings and facilities that have not traditionally been subject to CAA requirements. Assuming EPA does finalize GHG emission requirements for cars and trucks, the controlled gases would be “regulated air pollutants” and automatically swept into EPA permit programs. [See our October 23, 2009 Client Update, “US EPA Accelerates Pace of Climate Change Regulations.”] Moreover, the CAA specifies that EPA is to use the same kind of endangerment criterion in deciding whether to issue national ambient air quality standards. On December 2, 2009, the Center for Biological Diversity and 350.org, in fact, petitioned EPA to issue such standards for greenhouse gases. If ultimately successful, the petition could lead to state implementation plans establishing enforceable emission controls to meet a specific greenhouse gas ambient concentration. Today’s announcement thus could set the table for nationwide GHG controls even if Congress fails to enact new climate legislation.