An ancillary benefit of Greenhouse Gas (GHG) mitigation refers to a benefit derived from GHG mitigation that is in addition to the reduction in adverse impacts of global climate change. One type of ancillary benefits of GHG mitigation is reduced local conventional pollutants, which is associated with improved health. Middle-income countries like Thailand are in unique positions to obtain large ancillary health gains from reduced local conventional pollutants when GHG is mitigated by curbing fossil fuel consumption.