Ozone (O3)


  • ground-level ozone: secondary air pollutant produced in the troposphere from nitrogen oxide and volatile organic compounds when exposed to sunlight
  • fairly pungent smelling, colourless gas
  • low solubility in water
  • one of the strongest oxidants and irritant gases
  • highly corrosive to human, animal and plant tissue as well as materials

Main sources

  • motorised road transport (precursor pollutants nitrogen oxides)
  • industrial and commercial processes and installations (precursor pollutants volatile organic compounds)


    • irritates the respiratory mucosa, causes tightness in the chest, reduces lung function
    • is harmful to plants
    • contributes to the greenhouse gas effect (in the lower air layers)

    Ozone ambient limit values

    100 µg/m3 98% of the 1/2-h-means of a month of less than or equal to 100 µg/m3
    120 µg/m3 1-h-mean; may be exceeded once per year at most

    Status and changes

    From 1990 to 2014, nitrogen oxide emissions fell by around 50% and volatile organic compound emissions decreased by 70%. Despite rising mean ozone levels, this prevented an increase in the maximum values. In the summer months, the ambient limit values are frequently exceeded on a large scale.

      Last modification 15.09.2015

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