The Nickel Report

As I have reported previously, the US Court of Appeals for the DC Circuit issued a significant decision in September 2019 on EPA’s implementation of the so-called “Good Neighbor Provision” of the federal Clean Air Act (CAA). That is the CAA’s principal provision addressing what is often termed “interstate transport,” the physical process in which emissions from cars, trucks, factories, power plants, and myriad other sources—and the resulting air pollution—are carried by prevailing winds across state borders. The main purpose of the Good Neighbor Provision (section 110(a)(2)(D)(i)(I) of the CAA) is to prevent “significant contribution” by “upwind” states’ emissions to violations of national ambient air quality standards (NAAQS) in “downwind” states. Although states have the principal responsibility to implement this provision, EPA periodically has invoked its CAA authority to impose requirements to curb interstate transport when it determines upwind states have not adopted adequate controls.