Ozone and Volatile Organic Compounds

Ozone (O₃) is not emitted directly from any man-made source in any significant quantities. In the lower atmosphere, O₃ is primarily formed by a complex series of chemical reactions initiated by sunlight and acceleraated by high temperatures. These reactions can be summarised as the sunlight-initiated oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides (NO_x). The sources of VOCs are similar to those described for NO_x above, but also include other activities such as solvent use, and petrol distribution and handling.

The chemical reactions which produce ozone do not take place instantaneously, but can occur over hours or days; as a result, ozone measured at a particular location may have arisen from VOC and NO_x emissions many hundreds or even thousands of miles away. Maximum concentrations, therefore, generally occur some distance downwind of the original sources of precursor emissions.

Ozone has a wide range of health and ecosystem impacts. It irritates the eyes and airways of the lungs, increasing the symptoms of those suffering from asthma and lung diseases. In addition to its serious impacts on human health, ozone is also phytotoxic - damaging to many plants and commercial crops. It can also damage or age some man-made materials such as rubbers and elastomers, as well as bleaching paints and fabrics.