The U.S. electricity system faces multiple urgent challenges to address transmission needs, adapt to smart grid technologies, expand energy efficiency and renewable energy use, and meet increasingly stringent environmental requirements. Air quality management faces equally daunting challenges driven by the need for greater health and environmental protection, diminishing state and federal budgets, and aging regulatory approaches. Reliable, affordable, clean energy solutions are unlikely to occur unless energy and air regulators understand the obligations, structure, and processes in which each regulator acts, and use that knowledge to work together to simultaneously meet energy and air quality goals. The report begins by discussing some of the differences between state energy regulatory and air quality agencies and describing ways in which each can help the other. The Clean Air Act is described briefly, including its history, main goals, types of pollutants regulated, impacts of those pollutants, and the roles of the EPA and states in implementing the law. It then considers NAAQS, how they are developed, their components, and what happens when states fail to attain them. Finally, the SIP process is described, including how air regulations are developed and updated through that process.