Tropospheric pollution occurs due to the presence of gaseous and the particulate pollutants.
- Gaseous air pollutants. These include mainly oxides of sulphur (SO2, SO3), oxides of nitrogen (NO, NO2) and oxides of carbon (CO, CO2) in addition , to hydrogen sulphide (H2S), Hydrocarbons, ozone and other oxidants.
- Particulate pollutants. These include dust, mist, fumes, smoke, smog, etc.