PM2.5 has more complex sources and formation processes than SO2, creating a greater regulatory challenge. The chapter lays out new policies and standards to curb PM2.5. Shen then uses both satellite-based and officially reported data on PM2.5 concentration to examine its interplay with growth, stability, and regulation. Officially reported data reflect what subordinate leaders wish their superiors to know, while satellite-based data are more objective. The results show that before PM2.5 control entered promotion criteria, local leaders were incentivized to gradually order laxer regulation of polluters during their tenure for social stability and (reported) economic gains, resulting in political pollution waves. However, after certain prefectures’ evaluation criteria incorporated gradually more aggressive PM2.5 reduction, political pollution waves continued based on satellite-based statistics, though officially reported local monitor readings seemed to suggest much-attenuated pollution waves. Thus, changing incentives of local cadres and monitoring was insufficient to dampen PM2.5 pollution waves. The nature and complexity of individual pollutants matter for effective regulation.