More efforts required to reduce ozone pollution in Europe

Ozone is not directly emitted to the atmosphere but formed in complex photochemical reactions from ozone precursor gases (nitrogen oxides, carbon monoxide, methane and non-methane volatile organic compounds). Its production depends on meteorological conditions such as solar intensity and temperature. Elevated levels of ground-level ozone reduce agricultural crop yields and corrode infrastructure and cultural heritage. It can also cause health problems and lead to premature deaths.

The new EEA report ‘Air pollution by ozone across Europe during summer 2010’ shows that the long-term objective to protect human health (maximum daily eight-hour mean concentration of 120 µg/m³) was exceeded in all EU Member States and in most of the other reporting European countries at least once during summer 2010. As in previous years, the most widespread concentrations occurred in the Mediterranean area. However, areas of western and central Europe experienced higher ozone concentrations than in 2009.

Preliminary results show that 17 EU Member States (Austria, Bulgaria, Cyprus, the Czech Republic, France, Germany, Greece, Hungary, Italy, Luxembourg, Malta, Poland, Portugal, Romania, the Slovak Republic, Slovenia and Spain) are facing difficulties in meeting the target value for protecting human health. In all these countries, the maximum daily eight-hour mean ozone concentration of 120 µg/m³ was exceeded on more than 25 days during summer 2010.

Other key findings

• For the first time in four years, in 2010 the information threshold (a one-hour average ozone concentration of 180 µg/m³) was exceeded in northern Europe. The average number of threshold exceedances increased slightly in north-western, central and eastern Europe.

• The alert threshold (a one-hour average ozone concentration of 240 µg/m³) was exceeded 44 times in nine EU Member States with most exceedances in northern Italy and northern Portugal.
• Summer 2010 was characterised by a long period with numerous exceedances during the warm sunny weather experienced between 24 June and 22 July. This episode accounted for approximately 85 % of the total number of exceedances of the information threshold, 64 % of exceedances of the alert threshold and 52 % of exceedances of the long-term objective.

Target value for the protection of human health

Directive 2008/50/EC on ambient air quality and cleaner air for Europe sets out the ‘target value for the protection of human health’. Specifically, as of 2010 the maximum daily eight-hour mean concentration of ozone should not exceed 120 µg/m³ on more than 25 days per calendar year, averaged over three years. It further specifies that the target value will first be calculated using validated data from 2010 and following years. Therefore it will not be possible to assess exceedance of the target value fully until data for 2010, 2011 and 2012 have been compiled and validated.

Ozone pollution – not only a local air quality issue

In Europe, ozone concentrations in a particular country are also influenced by emissions in other northern hemisphere countries and by poorly regulated sectors such as international shipping and aviation. Thus, ozone pollution is not only a local air quality issue but also a hemispheric and global problem.

Data sources on emissions of ozone precursor gases

The EEA publishes emissions data on the air pollutants that contribute to the formation of ground-level ozone, available in several data viewers: NEC Directive viewer (NO_x, NMVOCs), LRTAP Convention viewer (CO) and the greenhouse gas data viewer (CH₄). Updated information on the trends in man-made emissions of ozone precursors NO_x and NMVOCs are also available in the recently published NEC Directive status report 2010.