Ozone levels still much too high

Figure: Number of days on which ozone concentrations exceeded the long-term objective for the protection of human health during summer 2011 (provisional data)

In the summer of 2011, the threshold for protecting human health from ozone was exceeded on more than 25 days in a significant part of Europe.

Despite efforts to mitigate ozone pollution, exceedances of EU ground-level ozone standards remained during summer 2011. The long-term objective for the protection of human health was exceeded in all EU member states and for more than 25 days in a significant part of Europe, according to the annual report on summer ozone levels by the European Environment Agency (EEA).

Ozone is a strong photochemical oxidant, which in elevated concentrations causes serious health problems and damage to materials and vegetation, including agricultural crops. Production of ground-level ozone is a result of chemical reactions between several air pollutants (ozone precursors) in the air and depends on weather conditions such as solar intensity and temperature. Precursor pollutants include nitrogen oxides, carbon monoxide, methane and non-methane volatile organic compounds. The main sectors that emit ozone precursors are road transport, power and heat generation plants, household (heating), industry, and petrol storage and distribution.

Ozone concentrations in Europe are also influenced by precursor emissions in other northern hemisphere countries and by emissions from international shipping and aviation. Consequently, ozone pollution is not only a local air quality issue but also a hemispheric and global problem.

The EEA reports that ozone levels exceeding target values in Europe were less frequent in summer 2011 than in previous years. However, the long-term objective (LTO) for the protection of human health (a maximum daily eight-hour mean concentration of 120 μg/m3) was exceeded in all EU member states and it is likely many of them will not meet the target value, applicable as of 2010.

The 2008 EU directive on ambient air quality and cleaner air for Europe (2008/50/EC) sets a long-term objective, a target value, an alert threshold and an information threshold for ozone (see Table) for the purpose of avoiding, preventing or reducing the harmful effects of ground-level ozone on human health and environment.

Table: Ozone threshold values, long-term objective and target value for the protection of human health, as set out in Directives 2002/3/EC and 2008/50/EC

(*) Not to be exceeded on more than 25 days per calendar year, averaged over 3 years; 2010 will be the first year for which the data are used in calculating compliance over the following 3 years.

Main findings of the report:

  • The information threshold and the LTO were both exceeded in the lowest proportion of air monitoring stations since the start of Europe-wide data reporting in 1997. This reduction was mainly due to unusually low temperatures and increased rainfall during the summer months, although there have also been some reductions in the emissions of ozone-precursor pollutants.
  • As in previous years, the LTO for the protection of human health was exceeded in all EU member states. Exceedances were registered at approximately 84 per cent of all stations, and the LTO limit was exceeded on more than 25 days in a significant part of Europe.
  • The information threshold was exceeded at monitoring sites in 16 EU member states and four non-member countries. It was exceeded at approximately 18 per cent of all operational stations. Only northern Italy and several more isolated locations reported a substantial number of exceedances.
  • The alert threshold was exceeded 41 times. Concentrations of 300 µg/m3 or more were measured three times in 2011, in Bulgaria, Italy and Spain.

The LTO threshold will be used to assess whether countries meet the directive’s target value (TV) for protecting human health. A preliminary assessment by the EEA indicates that exceedances of the target value occurred in 17 EU member states (Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, France, Germany, Greece, Hungary, Italy, Luxembourg, Malta, Poland, Portugal, Slovakia, Slovenia and Spain) and in five other countries (Croatia, Liechtenstein, the former Yugoslav Republic of Macedonia, Serbia and Switzerland). As in previous years, the most widespread concentrations occurred in the Mediterranean area.

Christer Ågren

Air pollution by ozone across Europe during summer 2011. EEA Technical report No. 1/2012. Can be downloaded at: http://www.eea.europa.eu/publications/air-pollution-by-ozone-2011


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