ISEE-80 Introduction: Rapidly developing regions often face critical air pollution problems due to the high concentrations of pollutants and the large number of people exposed. Decision-making regarding pollutant emissions, such as greenhouse gases, will affect long-term health through climate change, but also short-term health through more immediate changes in local pollution levels. We investigated the health and related economic benefits of modest changes in fossil for three case study cities in Latin America. Methods: We estimated the air pollutant concentrations of particulate matter and ozone for two “what if” scenarios for each of three case study cities (Mexico City; Santiago, Chile; and São Paulo, Brazil) from 2000 to 2020. The first scenario was based on current patterns of pollution (business-as-usual), whereas the second scenario assumed control policies to lessen ambient pollution emissions, such as those for carbon dioxide, methane, and other greenhouse gases. These concentrations were combined with locally-derived concentration-response functions to estimate the difference in health impacts for the two scenarios. Economic valuation of the difference in health endpoints is used to determine the health-related cost benefit of the lower emissions. Results: This research reveals that additional controls on fossil fuel would have enormous health benefits for Mexico City, São Paulo, and Santiago, averting about 32,000 deaths, 5 million asthma attacks, 200,000 child medical visits, and 50,000 cases of chronic bronchitis in the three cities over the 20 year period. Preliminary results indicate that in the year 2020 alone, the lowered pollution levels would prevent approximately 8,700 children’s medical visits in São Paulo, 80,000 asthma attacks in Mexico City, and 700 chronic bronchitis cases in Santiago. These and related health effects will be monetized to put the health-related economic benefits of lower emissions in perspective. Discussion: This work emphasizes the need for diligence regarding air pollution’s health effects and for attention to the local, short-term benefits of climate change mitigation strategies. This research demonstrates the magnitude of health advantages of modest control policies.