By Stephen Wiegand

On December 15, 2009, EPA published in the Federal Register its final endangerment findings with respect to greenhouse gases. See 74 Fed. Reg. 66496 (Dec. 15, 2009) []. This rulemaking is a response to Massachusetts v. EPA, 549 U.S. 497 (2007), in which the Supreme Court held that greenhouse gases were “pollutants” under the Clean Air Act and ordered EPA to determine whether greenhouse gases “may reasonably be anticipated to endanger public health or welfare” under Section 202 of the Act.
In its findings published on December 15, EPA concluded that six greenhouse gases taken in combination may reasonably be anticipated to endanger public health and public welfare. These gases include carbon dioxide, methane, nitrous oxide, hydroflourocarbons, perflourocarbons, and sulfur hexafluoride. In reaching these conclusions, EPA considered the extent to which elevated concentrations of greenhouse gases may cause changes in air quality, increases in temperature, changes in extreme weather events, increases in food- and water-borne pathogens, and changes in aeroallergens. EPA relied on assessments by the U.S. Global Climate Research Program, the Intergovernmental Panel on Climate Change, and the National Research Council.
While these findings do not in themselves impose any requirements on regulated entities, they are a prerequisite to future regulation of greenhouse gases under existing Clean Air Act authority. Many view the existing Clean Air Act as ill-suited to the regulation of greenhouse gases. This endangerment finding, along with EPA’s proposal to regulate greenhouse gases under existing Clean Air Act authority, see EPA Proposed PSD and Title V Greenhouse Gas Tailoring Rule [], is being used as a forcing function to accelerate the passage of stand-alone greenhouse gas legislation by Congress.