Ozone

Ground level ozone is a 'secondary pollutant'. It is not emitted directly to any significant extent but is produced in a range of chemical reactions fuelled by sunlight. The major pathway involves nitrogen oxides and VOC's reacting together to form ozone.

These reactions occur over a period of some hours, and ozone concentrators are frequently higher at a distance from the source of the nitrogen oxides.

The effects of ozone are again seen primarily in the respiratory system function. Short-term effects include changes in lung function measurements and inflammation. Higher and longer term exposure is related to more severe alterations in lung function. Sensitivity to allergens may also be increased, and there is some evidence to suggest that asthmatics are more sensitive to the effects of ozone than other members of the public. It is possible that the inflammatory response produced by exposure to ozone may last longer in asthmatic than in other people.