Air pollution by ozone across Europe during summer 2012
Despite efforts to mitigate ozone pollution, the number of exceedances of EU ground-level ozone concentration standards for protecting human health (Directive 2008/50/EC) remained at serious levels during summer 2012 (1).
In the summer of 2012, the threshold of 120 micrograms per cubic metre of air (ìg/m3) maximum daily eight-hour mean was exceeded on more than 25 days again across large parts of Europe. This is the threshold that will be used to assess whether countries meet the target value (TV) for protecting human health (2). Exceedances of this threshold occurred in 17 EU Member States (Austria, Bulgaria, Cyprus, the Czech Republic, France, Germany, Greece, Hungary, Italy, Luxembourg, Malta, Poland, Portugal, Romania, Slovakia, Slovenia and Spain) and five other countries (Albania, Croatia, the former Yugoslav Republic of Macedonia, Serbia and Switzerland). As in previous years, the most widespread concentrations occurred in the Mediterranean area.
The long-term objective (LTO) for the protection of human health (a maximum daily eight-hour mean concentration of 120 ìg/m3) was exceeded in all EU Member States except Estonia. The average number of LTO exceedances in 2012 was comparable with 2009–2011 years.
The so-called 'information threshold' (a one-hour average ozone concentration of 180 ìg/m3) was exceeded at approximately 28 % of all operational stations at least once during the summer, one of the lowest percentages since 1997. After a slight increase in occurrence of exceedances in 2010, there was a reduction of the information threshold exceedances in the years 2011 and 2012 back to levels seen in the years 2008 or 2009 in most European regions. In northern Europe, there were no exceedances of the information threshold in 2012, except for one in Denmark.
The so-called 'alert threshold' (a one-hour average ozone concentration of 240 ìg/m3) was exceeded in the 3 % of stations (only 25 times) during the summer, which is the lowest number on record.
The largest ozone episode in terms of area affected occurred between 24 and 28 July, and accounted for approximately 33 % of the total number of exceedances of the information threshold, 32 % of the exceedances of the alert threshold, and about 12 % of the exceedances of the LTO.
Ozone is a 'secondary' pollutant formed in the lower part of the atmosphere, the troposphere, from complex photochemical reactions following emissions of precursor gases such as nitrogen oxides (NOX) and volatile organic compounds (VOC) (Royal Society, 2008; US EPA, 2010 and 2011). Ozone, one of the air pollutants giving rise to the greatest concern in Europe, is a powerful oxidising agent.
Ozone concentrations in Europe are also influenced by emissions in other northern hemispheric countries, and by poorly regulated sectors such as international shipping and aviation. Thus, ozone pollution can no longer be considered a local air quality (AQ) issue — it is a hemispheric and global problem.
Ozone levels become particularly high in regions where considerable ozone precursor emissions combine with stagnant meteorological conditions during the summer, when high insolation and temperatures occur. In 2012, levels continued to exceed the long-term objective (LTO) established in EU legislation to protect human health.
This report provides an evaluation of ground-level ozone pollution in Europe for April–September 2012, based on information submitted to the European Commission under Article 10(2)(a) in Directive 2002/3/EC of the European Parliament and of the Council of 12 February 2002 relating to ozone in ambient air (EC, 2002), replaced by Directive 2008/50/EC (EC, 2008). Since EU Member States have not yet finally validated the submitted data, the conclusions drawn in this report should be considered as preliminary.
Directive 2002/3/EC requires EU Member States to report exceedances of the information threshold and alert threshold values (set out in Table 1.1) to the European Commission before the end of the month following an occurrence. Furthermore, by 31 October, EU Member States must provide additional information for the summer period (see Annex 1). This should include data on exceedances of the LTO for the protection of human health (a maximum daily eight-hour average concentration of 120 ìg/m3).
In order to make information available as promptly as possible, an overview of the monthly data provided by the countries is presented by the ETC/ACM on the EEA website (EEA, 2012d). In addition, the EEA's near-real-time 'Air quality levels in Europe' website (EEA, 2012b) shows provisional ground-level ozone levels across Europe, and provides up-to-date information (see Annex 3).