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You are here: Home / News / Heatwave sparks smog warnings through Europe

Heatwave sparks smog warnings through Europe

Concentrations of damaging ground-level ozone increase when summer sunshine ignites polluting emissions from transport and industry.

Read more in the EEA report "Europe's environment: the third assessment Chapter 5 - Air pollution ".

Concentrations of damaging ground-level ozone increase when summer sunshine ignites polluting emissions from transport and industry.

" End If

Current summer seasons ozone exceedances
For information on current summer seasons ozone exceedances reported by countries please visit our
European Topic Centre on Air and Climate Change
Ozone is a natural component of the atmosphere. Although it is a minor constituent, it is key to important atmospheric processes. Most ozone is in the stratospheric ozone layer. This "good ozone", protects life from dangerous ultraviolet radiation from the sun. However, direct exposure to ozone is hazardous and the "bad ozone" in ambient air at ground level has harmful effects on human health, on plants and on materials.

Ozone in ambient air is formed by chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOC) under influence of sunlight. Ozone concentrations can build up to high values during warm sunny days. Ozone concentrations today are much higher than a century ago due to emissions of NOx and VOC into the atmosphere from traffic, industry and other sources. Ozone is the main product of complex photochemical processes in the lower atmosphere involving oxides of nitrogen and volatile organic compounds as precursors of ozone formation. Ozone is a strong photochemical oxidant. Its elevated concentrations cause serious health problems and damage to ecosystems, agricultural crops and materials.

Map 1. Example of a smog episode: stations which reported an hourly ozone concentration in excess of 180 µg/m3, 17-19 and 22 June 2002 (all station types)
Source: map produced by the European Topic Centre on Air and Climate Change.

Ozone episodes, periods with elevated concentrations, mainly occur during periods of warm sunny weather. In Mediterranean countries, with prolonged spells of hot and sunny weather during the summer, ozone can quickly be formed and high concentrations can occur in the vicinity of urban centres. In northern Europe, the build-up of ozone is slower due to the more moderate weather conditions. Here, the highest levels are usually found downwind of cities.

The limit values set by the European Union to protect health are exceeded frequently for a large proportion of the EU’s population. Estimates for 1999, for example, suggest that 42% of the population was overexposed on 1-25 days, with 12% overexposed for more than 50 days. Only the Northern European countries and Portugal had less than 10 ‘exceedance days’. Although emissions of the substances that lead to ground level ozone are dropping, the reductions are unlikely to help meet either today’s or tomorrow’s targets, with north-west Europe expected to experience around 25 exceedance days per year by 2010. This is partly due to emissions in the whole northern hemisphere.

Scientific research has shown that ozone, NOx and VOC can be transported over distances of hundreds or even thousands kilometres. Under the Convention on Long-range Transboundary Air Pollution, countries in Europe and North America have agreed to reduce emissions according to the terms of a number of protocols.

In order to protect human health and the environment, the European Union, in legislation, has set targets and long-term objectives for ozone concentrations and will limit the national emissions of NOx and VOC. The legislation requires that citizens be properly informed about concentrations of ozone and other air pollutants.

More on ozone exceedance (summer 2002) in the EEA report Air pollution by ozone in Europe: Overview of exceedances of EC ozone threshold values during the summer season April-August 2002.

For information on current summer seasons ozone exceedances reported by countries please visit our
European Topic Centre on Air and Climate Change

Other reports from EEA on ozone exceedance in particular and air pollution in general:

Other sources for background information:

Several institutions are involved in the monitoring of ozone concentrations and can supply more topical information on specific regions.

National and regional web sites on recent ozone concentrations

Source: European Topic Centre on Air and Climate Change

Czech Republic
        Nordrein Westfalia
Switzerland fg_luft/luftbelastung/aktuell/grafiken/index.html
United Kingdom

Forecast web sites of ground-level ozone for regions in Europe

Source: European Topic Centre on Air and Climate Change

(Often only available in national languages)

Norwegian stations and
some European cities
Baltic region
United Kingdom
Denmark and NW Europe
Czech Republic
NW Europe and
Nordrein Westfalia

Read more

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