Health impacts

Up to 30% of Europe's urban population is exposed to ozone concentrations above the threshold levels set by the EU to protect health.

The main health effects of short-term (a few hours) exposure to ozone include irritation of throat and eyes, coughing, wheezing, inflammation of lungs and difficulties in breathing.

These effects may occur in people with respiratory diseases, children and the elderly when the ozone concentration reaches a level higher than 180 µg/m³ (EU information threshold). Above 240 µg/m³ (EU alert threshold), health effects will be increasingly severe and may be experienced by most individuals. See also: How can I protect my health?

Ozone at high concentrations leads to health problems, because it attacks the lining of our lungs. This can cause lung inflammation (irritation) even after only a few hours of exposure. Our airways respond to the exposure by covering the affected areas with fluid and by contracting the lung muscles. Breathing becomes more difficult and lung capacity decreases.

The lungs will usually recover within a few days after exposure to elevated concentrations of ozone. However, if ozone exposure is experienced over a longer period of time or on a number of repeated occasions within a year, chronic damage to lung tissue may occur. This means that the lung function may be affected and the lining may lose some of its ability to serve as a protective barrier against microbes, harmful chemicals and allergens.

Also, recent research studies suggest that long-term exposure to ozone may be associated with lung cancer. This possibility is expected to be further explored.

Table. Health effects associated with exposure to ozone. (Adapted from WHO 2004)

Asthma

Ozone can aggravate asthma and may also worsen other respiratory illnesses such as pneumonia and bronchitis. Evidence shows that when ozone concentrations are high, asthmatics have more attacks than usual and need more medication.

There is little evidence, however, to support the suggestion that the long-term upward trend in ozone pollution is the reason for the growing number of asthmatics. Asthma is now the most common respiratory disease among western European children, afflicting 7 % of children aged between 4 and 10.

Children’s health

Children are particularly sensitive to air pollution, because they breathe more air per kilogram of body weight and have smaller lungs than adults. Also, children – especially newborn babies – are vulnerable because their metabolism and lung defence mechanisms are not fully developed.

Evidence indicates that long-term ozone exposure reduces the development of the lung function in children. This may contribute to a shorter life expectancy, because decreased lung function is one of the strongest predictors of increased mortality in adults.

There is also evidence that high exposure to ozone increases the occurrence of lung infections (e.g. pneumonia and coughing) in children.