Communities for a Better Environment v. Environmental Protection Agency, 748 F.3d 333

EPA reviewed the National Ambient Air Quality Standards (NAAQS) for carbon monoxide (CO) in 2007–2011 and issued a Final Rule in 2011 retaining the existing primary standards (8-hr 9 ppm; 1-hr 35 ppm) and declining to adopt a secondary standard.
Petitioners: Communities for a Better Environment, WildEarth Guardians, and Sierra Club challenged both decisions as arbitrary and capricious.
Primary-standard issue: petitioners relied on epidemiological studies and urged EPA to tighten the primary NAAQS to better protect human health.
Secondary-standard issue: petitioners argued EPA must set a secondary standard to protect public welfare (including climate), contending CO contributes to climate change.
EPA defended retention of the primary standard based on its assessment that evidence did not show causation at current levels and explained uncertainties about CO effects on climate as to the secondary standard.
The D.C. Circuit upheld EPA’s retention of the primary standard and held petitioners lacked Article III standing to challenge EPA’s refusal to adopt a secondary CO standard.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether EPA’s retention of the existing primary CO NAAQS was arbitrary and capricious	Epidemiological studies show health harms at levels allowed by current primary standards, so standards are inadequate	EPA reasonably concluded studies show correlation not causation at NAAQS levels; toxicology/clinical evidence does not corroborate causation	Court upheld EPA: retention was reasonable and not arbitrary or capricious
Whether EPA unlawfully refused to adopt a secondary CO standard to protect public welfare/climate	CO contributes to climate change; a secondary standard would mitigate welfare harms	EPA showed significant scientific uncertainty about CO’s effect on climate and could not show a secondary standard would affect climate/welfare	Court dismissed challenge for lack of Article III standing—petitioners failed to show causation/redressability

Whitman v. American Trucking Associations, Inc., 531 U.S. 457 (2001) (describes statutory standard-setting framework and "requisite" requirement for NAAQS)
National Telephone Cooperative Ass'n v. FCC, 563 F.3d 536 (2009) (arbitrary-and-capricious review requires agency action be reasonable and reasonably explained)
Lead Industries Ass'n v. EPA, 647 F.2d 1130 (D.C. Cir. 1980) (deference to agency in setting NAAQS and scientific judgments)
City of Waukesha v. EPA, 320 F.3d 228 (D.C. Cir. 2003) (extreme deference to agency on scientific matters)
National Environmental Development Ass'n's Clean Air Project v. EPA, 686 F.3d 803 (D.C. Cir. 2012) (review of EPA’s use of epidemiological evidence in NAAQS decisions)
ATK Launch Systems, Inc. v. EPA, 669 F.3d 330 (D.C. Cir. 2012) (arbitrary-and-capricious standard in agency rulemaking)
American Trucking Associations, Inc. v. EPA, 283 F.3d 355 (D.C. Cir. 2002) (role of Clean Air Scientific Advisory Committee and deference to EPA science judgments)
American Petroleum Institute v. Costle, 665 F.2d 1176 (D.C. Cir. 1981) (deference to agency expertise)
Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir. 1976) (en banc) (standards for judicial review of EPA scientific determinations)
Massachusetts v. EPA, 549 U.S. 497 (2007) (state standing to challenge EPA regulation of greenhouse gases)
Sierra Club v. EPA, 292 F.3d 895 (D.C. Cir. 2002) (standing and causation principles in environmental challenges)