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Ground-level ozone

An important group of pollutants are the photochemical oxidants. Common to these is that they are formed by other pollutants in the air through the action of sunlight, and they are highly reactive.

The ozone layer in the stratosphere, at an altitude of 10—40 kilometers, protects us from ultraviolet radiation from the sun and is an essential requirement for all higher life on the Earth. When ozone is present at ground level it may be harmful to people, animals, plants and materials.

Ozone is a powerful oxidant and can give rise to eye irritations and irritations of the airways that lead to a reduction in lung capacity, even at relatively low concentrations. Because ozone is a gas with low solubility in water it can penetrate deep into the lungs. During periods of elevated levels a larger number of people are admitted to hospital emergency departments with respiratory problems. Long-term exposure, even to relatively low concentrations, can lead to permanent lung damage.

In plants, it has been found that damage can occur at concentrations only slightly higher than current background levels. This has a significance on yields from agriculture and forestry, as well as affecting natural ecosystems.

Ozone formation and traveling

Ozone is formed as a result of photochemical reactions, where nitrogen oxides, oxygen and volatile organic compounds are involved. The concentration of ozone is generally highest on sunny days in late spring and summer, during periods of high pressure. Sunshine accelerates ozone formation, and the high pressure means that air masses move slowly, resulting in little mixing of the air.

Once ozone has formed it can be carried considerable distances in the air. Periods when levels rise temporarily due to movement of this type are generally referred to as episodes. Ozone is very much a trans-boundary air pollution problem.

Source: Air and the environmentexternal link, opens in new window by P.Elvingson and C.Ågren.

Updated: 2012-10-16
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