pollution from factories and power plants has been the classic example for the concepts of external or social cost while long considered a beneficial sideeffect of decarbonisation pollution control efforts are increasingly the primary policy driver for reducing fossil fuel use in power generation with the reduction of greenhouse gas ghg being a welcome sideeffect indeed in most climate change mitigation studies the benefits from reducing human exposure to pm s and nox outweigh the benefits of reducing ghg emissions and the resulting climate change mitigation which offers new perspectives for internalisation