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Ozone injury

Ozone injury - Charateristic ozone leaf reddening
  • Latin name: Veneficium oxygenum Humain
  • French name: Intoxication à l'ozone
  • Division: Pollutio
  • Class: Vaporifera
  • Synonym(s): Atmospheric impurity (O3) ,
    Ozone gazeux (O3) ,
    Pollution d'ozone (O3)


Leaf, Needle



Damage, symptoms and biology

Ozone, a gas that is present in the upper atmosphere, specifically in the stratosphere, plays a beneficial role by absorbing much of the ultraviolet radiation from the sun. While natural ozone concentrations do exist at ground level, they are very weak and do not pose a serious environmental threat. Human activities, coupled with the oxidizing effect of solar radiation, induce the formation of additional ground-level ozone. Polluting emissions resulting from the use of fossil fuels cause the formation of toxic gases such as NOx and SOx. When there is a build-up of these gases and smog forms, incoming solar radiation oxidizes the oxygen molecules, thus causing more ozone to form. The build-up of ozone concentrations causes a change in the colour of foliage, wilting and, in some cases, premature leaf-fall.

Other information

Warm, humid days with little wind are favourable for ground-level ozone formation. Most large cities have a smog alert system.

Canadian Forest Service Publications

Ozone injury

Information on host(s)

Main host(s)

Conifer, deciduous


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