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Why it Matters
The Clean Air Act’s “good neighbor” provision requires upwind states to ensure that the air pollution they create does not affect downwind states’ ability to meet the National Ambient Air Quality Standards (NAAQS). Downwind states rely on this provision to protect their residents’ health. States are required to address interstate pollution in their State Implementation Plans for implementing the NAAQS.
A downwind state can file a Clean Air Act section 126 petition asking EPA to regulate pollution from sources in another state when that pollution is moving across state lines and impairing interstate air quality. Additionally, Section 176A of the Clean Air Act authorizes EPA to establish a transport region of states that contribute significantly to a NAAQS violation. Section 184 established such a region for ozone—the Ozone Transport Region (OTR)—for the northeast and mid-Atlantic and requires certain control requirements to address interstate ozone pollution transport within the OTR.
To address regional transport in the eastern half of the US, EPA established the Cross-State Air Pollution Rule (CSAPR) to require upwind states to reduce interstate pollution of soot and smog contributors, sulfur dioxide (SO2), and oxides of nitrogen (NOx), and ensure downwind states can meet the National Ambient Air Quality Standards (NAAQS) for the 2008 ozone standard.
In 2020, in response to section 126 petitions, the D.C. Circuit denied Delaware’s petition, granted Maryland’s petition in part, and vacated EPA’s denial of New York’s petition (returning the petition to EPA for reconsideration).
A group of eastern states and D.C. also asked EPA in 2020 under section 184(c) to require Pennsylvania to further regulate its coal-fired power plants. EPA held a public hearing on February 2, 2021 and released information that it believed “may be relevant in reaching a decision on the recommendation.” Comments were due April 7, 2021.
On March 15, 2021, the Biden EPA issued a final rule updating the CSAPR for the 2008 ozone NAAQS, which EPA states resolves 21 states’ outstanding interstate ozone transport obligations with respect to the 2008 ozone NAAQS. This rule was in response to the D.C. Circuit’s remand of the CSAPR Update in Wisconsin v. EPA and also responds to the D.C. Circuit vacatur of the CSAPR Close-Out in New York v. EPA. The court had determined that the CSAPR Update rule was unlawful as it would have allowed states to continue their significant contributions to downwind ozone problems beyond their attainment dates.
For the transport related to the 2015 ozone standard, EPA has entered into consent decrees that obligate EPA to approve certain state SIPs by April 30, 2022 or propose a transport rule by February 22, 2022 and a final transport rule by December 15, 2022.