American Lung Association v. Environmental Protection Agency

Section 111 of the Clean Air Act (CAA) required the Environmental Protection Agency (EPA) (defendant) to regulate new and existing stationary sources of air pollutants (i.e., immovable sources of pollution such as buildings) that caused or contributed significantly to air pollution. Power plants were among the stationary sources subject to regulation pursuant to § 111 and were required to meet established standards of performance. For purposes of the CAA, a standard of performance was an emissions standard that reflected the degree of emissions limitation achievable using the best system of emission reduction. In 2007, the United States Supreme Court ruled that greenhouse-gas emissions were air pollutants within the meaning of the CAA. The EPA subsequently found that it was urgently necessary to reduce greenhouse-gas emissions because they were damaging the environment and endangering humans’ health and welfare. Accordingly, the EPA formulated the Clean Power Plan, which concluded that the best system of reducing greenhouse-gas emissions from power plants involved: (1) improving the heat rate at coal-fired power plants to reduce the amount of coal needed for electricity production, (2) substituting increased electricity generation from lower-emitting natural-gas combined-cycle units for generation from higher-emitting coal-fired power plants, and (3) prioritizing the use of electricity generated from zero-emitting renewable-energy sources over electricity from higher-emitting, heavily polluting fossil-fuel-fired power plants. The EPA used this best system to calculate achievable emissions reductions and publish emissions guidelines. Generation-shifting methods adopted by power plants to prioritize using the cleanest sources of power were successfully and efficiently achieving emissions reduction in a cost-effective way. However, in 2019, the EPA issued the Affordable Clean Energy (ACE) rule, which repealed and replaced the Clean Power Plan. According to the EPA, repeal was necessary because § 111 limited the best system of emission reduction to measures that could be put into operation at the stationary source itself, but the Clean Power Plan’s best system incorporated generation substitutions and emissions trading that could not be implemented on-site at coal-fired power plants. The ACE rule identified a new best system of emission reduction for coal-fired power plants that was based primarily on upgrading existing equipment to improve heat rates. Petitioners including the American Lung Association (plaintiffs) petitioned for review of the ACE rule.