Molecular formula: O3
Characteristics: This odourless gas usually occurs in the atmosphere, where it protects the Earth against ultraviolet radiation. It is dangerous near the Earth’s surface.
Occurrence: Arises from the reactions of precursors, which are nitrogen oxide and organic substances with solar radiation. Transport, power plants, and industry are the sources of the precursors.
Impact: Ground-level ozone ingestion may cause asthma, chest, or throat pain. Moreover, ground-level ozone diminishes the function of the liver and irritates the lungs.
Limit: The maximum daily 8-hour average in the EU is 120 µg/m3.