My dissertation investigates these questions in the context of programs and policies that are important in their own right. Chapters 1 and 2 of my dissertation explore the economic costs and distributional implications associated with the largest environmental regulatory pro- gram in the United States, the Clean Air Act. Chapters 3 and 4 examine the social costs of air pollution in the context of transportation externalities, showing how effective transportation policy has additional co-benefits in the form of environmental policy. My dissertation remains unified in both its subject matter and methodological approach - using unique sources of data and sound research designs to understand important issues in environmental policy.