Background
In December 2024, the Environmental Protection Agency completed a review of secondary national ambient air quality standards for nitrogen oxides, sulfur oxides, and particulate matter. EPA retained the existing standards for nitrogen oxides and particulate matter and tightened the sulfur-oxides standard to a three-year annual average of 10 parts per billion.
Before issuing the final rule, EPA determined that it would have no effect on species or critical habitat protected by the Endangered Species Act. EPA reasoned that the revised sulfur-oxides standard would not control emissions because the existing primary standard remained more stringent in practice, while retaining the other standards would require no new pollution controls or attainment designations. The Center for Biological Diversity petitioned for review, arguing that EPA arbitrarily ignored ongoing and cumulative harms to protected species and made its effects determination too late.
The Court’s Holding
The D.C. Circuit denied the petition. It first held that the Center had associational standing because its members had aesthetic and recreational interests in protected species exposed to the pollutants, record evidence linked continued pollution to risks of harm, and consultation could potentially lead EPA to adopt more protective standards.
On the merits, the court held that EPA reasonably found no effects attributable to the 2024 rule. Under the applicable regulatory definition, an environmental consequence must satisfy but-for causation to qualify as an effect of an agency action. Any ongoing or cumulative pollution harms would persist without the rule because the rule did not alter the controlling emissions requirements. The court also held that EPA timely completed its effects determination two months before final action; neither the ESA nor its regulations imposed a more specific deadline. It assumed without deciding that retaining the nitrogen-oxides and particulate-matter standards constituted agency action under the ESA.
Judge Henderson joined the opinion in full but wrote separately that retaining existing standards was inaction that did not trigger consultation at all. She agreed that, even if it were agency action, EPA’s no-effect determination was timely and lawful.
Key Takeaways
- An ESA effects determination requires a causal connection between the challenged federal action and the asserted effects; harms that would occur regardless of the action do not satisfy but-for causation.
- EPA reasonably relied on attainment designations, implementation requirements, and air-quality data to conclude that the rule would not change emissions or environmental conditions.
- The requirement to make an effects determination at the “earliest possible time” allows flexibility, and a determination completed before final agency action was timely here.
Why It Matters
The decision limits ESA consultation challenges based solely on continuing environmental harms when the challenged agency action does not cause those harms or change the regulatory mechanisms governing them. Even the ESA’s low “may affect” threshold does not eliminate the need to connect the asserted effects to the particular agency action under review.
The court also confirmed that an agency may establish standing-related causation and redressability differently from merits-related causation: the Center had standing under relaxed procedural-injury principles, yet lost because the rule itself was not the but-for cause of the environmental effects asserted.