Ozone

Ozone

Ozone is a gas that exists naturally in the upper layers of the earth's atmosphere. At that altitude it is one of the earth's great protectors but when it occurs at ground level it is linked to pollution. Stratospheric ozone shields us from some of the potentially harmful excessive ultraviolet radiation from the sun. In the 1980s it was discovered that emissions of gases from engineering activities were causing a `hole' in the ozone layer. There is concern that this will increase the risk of skin cancer, eye cataracts and damage to crops and marine life.

At ground level, sunlight reacts with motor vehicle exhaust gases to produce ozone. Human lungs cannot easily extract oxygen (O₂) from ozone (0₃) so causing breathing difficulties and irritation to the respiratory channels. It can also damage plants.

This ground level or tropospheric ozone is a key constituent of what is called photochemical smog or summer smog. In the UK it has increased by about 60% in the last 40 years.