EPA Changes Definition of “Ambient Air,” Allows an Increase in Dangerous Pollution

December 3, 2019
Sharyn Stein, 202-572-3396, sstein@edf.org

(Washington, D.C. – December 3, 2019) EPA today finalized a change to the basic definition of air pollution in America’s most important clean air law.

The agency released a document claiming to reinterpret its longstanding definition of “ambient air” in the Clean Air Act. The change would allow more pollution by narrowing the scope of the ambient air that EPA evaluates when determining whether pollution levels exceed national health-based standards.

“EPA is adopting a deeply flawed approach that would ignore harmful levels of air pollution if that pollution occurs within land owned by an industrial source. However, there is no ‘public’ or ‘private’ air. EPA’s action will result in more pollution in the air we breathe,” said EDF attorney Rachel Fullmer.

Under the Clean Air Act, EPA establishes national, health-based standards for certain harmful pollutants. In carrying out this duty, EPA assesses pollution levels in the “ambient air,” which for decades the agency has defined as “that portion of the atmosphere, external to buildings, to which the general public has access.” These health-based limits on levels of pollution in the ambient air form the foundation of the Clean Air Act.

EPA is now attempting to upset this longstanding approach by expanding exemptions that would allow an industry to emit more pollution into the outdoors as long as the pollution technically goes into the air at a site it owns, and as long as the source posts warning signs or “deploys other measures.”

The new policy would apply to all types of air pollution – including harmful pollutants like ground-level ozone, the primary component of smog, particulate pollution, which is linked to serious heart and lung diseases and has been increasing in recent years, and greenhouse gases, which cause climate change. The change would also weaken EPA’s ability to monitor and model some of the most dangerous types of air pollution.

EPA did not open a formal public comment period on the change. EPA’s final document was signed on November 22 but just released change to the public this morning.

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