Ozone pollution in Europe: fewer alert days but concentrations still high

News Published 06 May 2015 Last modified 21 Jun 2016
2 min read
Photo: © r.g-s
Air pollution by ground-level ozone continued to affect many countries across Europe during summer 2014, according to a new briefing published by the European Environment Agency (EEA). Almost all reporting countries exceeded at least once the long-term objective set by EU legislation, while the stricter alert threshold was exceeded only on four occasions.

Exposure to high concentrations of ground-level ozone can cause and aggravate cardiovascular and respiratory diseases. The European Union's Air Quality Directive sets four standards to reduce air pollution by ozone and its impacts on health:

  • information threshold: 1-hour average ozone concentration of 180 μg/m3,
  • alert threshold: 1-hour average ozone concentration of 240 μg/m3,
  • long-term objective: the maximum daily 8-hour mean concentration of ozone should not exceed 120 μg/m3,
  • target value: long-term objective should not be exceeded on more than 25 days per year, averaged over 3 years. 

Concentrations of ground-level ozone significantly exceeded these standards during summer 2014, according to the EEA's latest analysis. However, the number of exceedances was lower than in many previous years, in line with the long-term downward trend observed over the last 25 years.

Depending on which threshold is exceeded, authorities in the affected areas and countries have to take specific measures. For example, exceeding the information threshold triggers an obligation to inform the population on possible risks, while exceeding the alert threshold requires authorities to take immediate action.

Key facts – summer ozone 2014

  • Measurements were reported from 1607 monitoring stations across 30 European countries.
  • Approximately 80% of these stations recorded at least one exceedance of the long-term objective between April to September 2014, with exceedances occurring in all reporting countries except Croatia, Estonia, Ireland, Romania and Serbia.
  • Seven EU Member States (Austria, Cyprus, France, Germany, Hungary, Luxembourg, and Spain) had stations where ozone levels exceeded the long-term objective on more than 25 days. This corresponds to 6% of all reporting stations, affecting approximately 1% of the total population in the reporting countries.
  • Averaged over the past three years, 16 countries (Austria, Bulgaria, Croatia, Cyprus, the Czech Republic, France, Germany, Hungary, Luxembourg, Poland, Portugal, Serbia, Slovakia, Slovenia, Spain and Switzerland) exceeded the 2012 target value.
  • Ozone concentrations higher than the information threshold were reported from monitoring stations in 18 countries. No exceedances were reported by Andorra, Bulgaria, Croatia, Estonia, Finland, Ireland, Lichtenstein, Lithuania, Romania, Serbia, Slovenia and Sweden.
  • Ozone concentrations higher than the alert threshold were reported only in France, on four occasions.
  • Approximately 36% of the exceedances of the information threshold, 75% of exceedances of the alert threshold, and 20% of long-term objective exceedances took place during a single episode of high concentrations between 7 and 14 June 2014.


More detailed information on ozone measurements in each country as well as background information on ozone are available in the briefing.

Note: This summer ozone assessment is based on provisional data and is subject to change. Countries will report verified air quality data for 2014 by September of this year.

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