In the troposphere (lower atmosphere), ozone is considered a pollutant. It is formed here as the result of pollution by volatile organic compounds (VOCs), carbon monoxide, carbon dioxide, black carbon or soot, unburned hydrocarbon, oxides of nitrogen (NOx), and oxides of sulfur.
The main sources of VOCs and nitrogen oxides are road transport, solvent release from drying paints, glues, or inks, and petrol handling and distribution.
