Criteria Air Contaminants - EPA Endangerment Findings/ Mass V. EPA

EPA Endangerment Findings/ Mass V. EPA

In 2009, the EPA Administrator found that under section 202(a) of the Clean Air Act greenhouse gases threaten both the public health and the public welfare, and that greenhouse gas emissions from motor vehicles contribute to that threat. This final action has two distinct ‘findings,’ which are:

1) The ‘Endangerment Finding’ in which the Administrator found that the mix of atmospheric concentrations of six key, well-mixed greenhouse gases threatens both the public health and the public welfare of current and future generations. These six greenhouse gases are: carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆). These greenhouse gases in the atmosphere constitute the “air pollution” that threatens both public health and welfare.

2) The ‘Cause or Contribute Finding,’ in which the Administrator found that the combined greenhouse gas emissions from new motor vehicles and motor vehicle engines contribute to the atmospheric concentrations of these key greenhouse gases and hence to the threat of climate change.

The EPA issued these endangerment findings in response to the 2007 supreme court case Massachusetts v. EPA, when the court determined that greenhouse gases are air pollutants according to the Clean Air Act. The court made the decision that the EPA must determine whether greenhouse gas emissions from new motor vehicles “cause or contribute to air pollution which may be reasonably be anticipated to endanger public health or welfare, or whether the science is too uncertain to make a reasoned decision" (EPA’s Endangerment Finding).

The EPA determined that, according to this decision, there are six greenhouse gases that need to be regulated. These include:

• carbon dioxide (CO₂)
• methane (CH₄)
• nitrous oxide (N₂O)
• hydrofluorocarbons (HFCs)
• perfluorocarbons (PFCs)
• sulfur hexafluoride (SF₆)

This action allowed the EPA to set the greenhouse gas emission standards to light-duty vehicles proposed jointly with the Department of Transportation’s Corporate Average Fuel Economy (CAFE) standards in 2009.