Air pollution is a global killer and predominantly an urban one, responsible for about 7 million premature deaths worldwide each year. Air pollution by particulate matter (PM) in cities can be reduced through system-based approaches focusing on better use of natural resources and better design of urban infrastructures and industries. This case study applies a systems approach to demonstrate the potential economic benefits, resource-savings, reductions in greenhouse gases (GHG) and PM emissions, air quality improvements and associated health co-benefits achievable by implementing key circular economy strategies in all 637 cities in mainland China.