The air pollution levels in several big cities frequently exceed the National Ambient Air Quality Standards (NAAQS), especially for particulate matter (PM) and ground-level ozone, as highlighted in Chapter 1 of this book. Rapid population growth, industrialization, and urbanization result in high emissions of primary PM and major precursors for formation of secondary PM, ozone, and acid deposition in urban areas. Understanding the complex relationships between the source emission and the multiple air pollution issues is required to assess the present and project future effects of various development scenarios on the human health and environment. In particular, analysis of causal links between emissions and meteorology with the atmospheric concentrations and deposition of air pollutants is essential for development of the integrated air quality management (AQM) strategies.