This book develops a macroeconomic theory that explains the environmental Kuznets curve (EKC) phenomenon. With a detailed review of the EKC literature according to different sources of pollutant, this book not only discusses the historical advances in testing the EKC hypothesis but also suggests some econometric methods that can modify the traditional ways of EKC tests. The empirical analysis in this book focuses on some high-income OECD economies in the issue of the emissions of two typical air pollutants, sulfur dioxide and carbon dioxide.