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National ambient air quality standards (NAAQS), §109

WildEarth Guardians v. Environmental Protection Agency

The D.C. Circuit upheld EPA's compliance deadlines for states to meet the NAAQS for fine particulate matter (PM2.5). The court previously had ruled that the framework EPA had been applying to PM2.5 was incorrect, and ordered the Agency...

Sierra Club v. United States Environmental Protection Agency

A district court ordered EPA to impose a "good neighbor” federal implementation plan (FIP) for Texas with respect to the 1997 fine particulate matter (PM2.5) NAAQS. In 2015, the D.C. Circuit...

Environmental Integrity Project v. United States Environmental Protection Agency

A district court dismissed environmental groups' CAA citizen suit against EPA for failing to respond to their 2011 petition concerning ammonia gas pollution. In 2011, the groups petitioned EPA asking it to find that ammonia gas...

EME Homer City Generation, L.P. v. Environmental Protection Agency

The D.C. Circuit, on remand from the U.S. Supreme Court, invalidated EPA's 2014 emissions budgets under the transport rule, also known as...

Mississippi Commission on Environmental Quality v. Environmental Protection Agency

The D.C. Circuit denied petitions for review of EPA decisions regarding nonattainment designations under the 2008 ozone NAAQS. Several states, counties, industrial entities, and environmental organizations petitioned the court...

Westar Energy, Inc. v. Environmental Protection Agency

The D.C. Circuit denied petitions for review challenging EPA's disapproval of a revision to Kansas' proposed SIP revision for the 2006 fine particulate matter (PM2.5) NAAQS. EPA disapproved the SIP revision because the submission lacked...

Save the Scenic Santa Ritas v. Darwin

An Arizona court overturned the state's issuance of an air permit for a proposed open-pit copper mine. An environmental group argued that the state's approval of the permit was arbitrary and capricious because the mine has the potential...

Natural Resources Defense Council v. Environmental Protection Agency

The D.C. Circuit held that EPA's regulations implementing the 2008 NAAQS for ozone exceed the Agency’s authority under the CAA. In 2008, EPA revised and strengthened the standards for ozone pursuant to the CAA. One of the revisions...

Center for Biological Diversity v. Environmental Protection Agency

The D.C. Circuit upheld EPA’s decision to defer adopting new secondary NAAQS for oxides of sulfur (SOx) and nitrogen (NOx) pending further scientific study. Citing doubts about the accuracy of its aquatic acidification index model—used...

National Ass'n of Manufacturers v. Environmental Protection Agency

The D.C. Circuit denied industry groups' petition for review challenging EPA's 2013 primary NAAQS for fine particulate matter. In the final rule, EPA lowered the level of the particulate matter NAAQS from 15.0 μg/m3 to 12.0 μg/m3, a...