Other environmentally important polluting substances are emitted to air beyond GHGs and ODSs. The most important are the different fractions of PM, which is an air pollutant consisting of mixed solid (i.e., dust) and liquid particles suspended in the air. Furthermore, the particulate material contains different chemical elements and compounds that can be harmful beyond the potential impact of dust. For example, PM can contain chemical constituents such as sulphates, nitrates and ammonium.