Airborne particulate matter (PM) contributes to air pollution that is the 3rd leading cause of death worldwide. This study uses molecular markers (a chemical species specific to an emission source) to identify and quantify PM sources in Nepal, where air pollution is severe. Biomass burning, garbage burning, fossil fuel, and cow dung burning are major sources of PM. This quantitative understanding of pollution sources will be aid in planning and evaluating pollution mitigation strategies.