This indicator shows the exposure of areas covered with specific vegetation (crops and forests) to ground-level ozone.
Ground level ozone is one of the most prominent air pollution problems in Europe, mainly due to its effects on human health, crops and natural ecosystems. When absorbed by plants, it damages plant cells, impairing their ability to grow and reproduce, and leading to reduced agricultural crop yields, decreased forest growth and reduced biodiversity.
The risk is estimated by reference to either a target value and a long-term objective, or to the 'critical level' for ozone for each location. The target value and the long-term objective are levels fixed with the aim of avoiding, preventing or reducing harmful effects on the environment. For ozone, the critical level is a concentration in the atmosphere, above which direct adverse effects on receptors, such as human beings, plants, ecosystems or materials, may occur according to present knowledge .
Methodology for indicator calculation
AOT40 estimated values are calculated from hourly data at all rural background stations available in the Air Quality e-reporting database (former AirBase). Only data series with more than 75 % valid data are considered.
The AOT40 maps have been created by combining measurement data from the rural background stations combined with the results of the EMEP dispersion model, altitude field and surface solar radiation in a linear regression model, followed by the interpolation of its residuals by ordinary Kriging. For altitude, dataset GTOPO30 (Global Digital Elevation Model) at a resolution of 30x30 arcseconds has been used. The solar radiation has been obtained from ECMWF's Meteorological Archival and Retrieval System (MARS). Kriging is a method of spatial statistics that makes use of spatial autocorrelation (the statistical relationship between the monitoring points expressed in the form of variograms). Kriging weights the surrounding measured values to derive an interpolation for each location. The weights are based (i) on the distance between the measured points and the interpolated point, and (ii) on the overall spatial arrangement among the measured points. The type of Kriging at its parameters (in particular the parameters describing the semivariogram) is chosen in order to minimise the RMS error.
The AOT40 maps have been overlayed in a geographical information system with the land cover CLC2018 map. The resolution was 2x2km2 to generate maps for the agricultural area at risk due to ozone exposure. Exposure of the agricultural area (defined as the CORINE land cover level-1 class 2 Agricultural areas, encompassing the level-2 classes 2.1 Arable land, 2.2 Permanent crops, 2.3 Pastures and 2.4 Heterogeneous agricultural areas) and forest areas (defined as the CORINE land cover level-2 class 3.1. Forests) have been calculated at the country-level.
AOT40 is used to be in line with the Air Quality Directive [1]. However, in considering the latest scientific knowledge concerning vegetation ozone exposure, it should be noted that, at present, ozone impacts on vegetation are better modelled by fluxes of ozone into stomatal openings of vegetation .
Methodology for gap filling
In the AOT40-mapping, Türkiye has been excluded up to 2015 (the 2016 map was the first time it was included) due to the lack of reported measurements at rural background stations. In the exposure estimates, the number of countries has been growing since 2004. Figures 1 and 2 show the situation in individual years and not a trend.
This indicator provides relevant information for the EU's Eighth Environmental Action Programme (8th EAP). The 8th EAP supports the objectives of the European Green Deal in line with the long-term objective to live well, within the planetary boundaries by 2050 at the latest, as already established in the 7th EAP.
The 8th EAP aims to accelerate the green transition to a climate-neutral, sustainable, non-toxic, resource-efficient, renewable energy-based, resilient and competitive circular economy in a just, equitable and inclusive way, and to protect, restore and improve the state of the environment by, inter alia, halting and reversing biodiversity loss. It supports and strengthens an integrated policy and implementation approach, building upon the European Green Deal.
Internationally, a first step to address air-pollution related impacts on health and the environment was the 1979 United Nations Economic Commission for Europe (UNECE) Geneva Convention on Long-range Transboundary Air Pollution (LRTAP or Air Convention).
A centrepiece of the convention is the 1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-level Ozone, subsequently amended in 2012. Critical ozone levels for vegetation were also defined under the Air Convention.
The Air Quality Directive sets both a target value (to be met in 2010) and a long-term objective for ozone for the protection of vegetation. The long-term objective is largely consistent with the long-term critical level of ozone for crops, as defined in the UNECE LRTAP Convention.
Targets
UNECE CLRTAP Gothenburg Protocol (1999; amended in 2012)
Using a stepwise approach and taking into account advances in scientific knowledge, the long-term target under the amended protocol is that atmospheric depositions or concentrations do not exceed for parties within the geographical scope of EMEP, the critical levels of ozone, as given in Annex I.
Annex I of the amended protocol includes a short definition of critical levels for ozone.
Critical levels for the protection of crops and forests (AOT40f) have also been defined under the Air Convention. The critical level for crops is consistent with the EU long-term objective for vegetation. The critical level for forests relates to the accumulated sum during the growing season (considered as April to September) and is set at 10,000μg/m3·h.
Air Quality Directive (2008/50/EC)
For the protection of vegetation from ozone exposure, the Air Quality Directive defines:
a) the target value for the protection of vegetation as AOT40-value (calculated from hourly values from May to July, considering the growing season) of 18,000 (μg/m3)·h, averaged over 5 years. This target value should be met in 2010 (2010 being the first year from which data will be used in the calculation over the following 5 years).
b) a long-term objective as AOT40-value (calculated from hourly values from May to July) of 6,000 (μg/m3)·h, with no defined date of attainment.
In the assessment part of the indicator, the target value threshold is also considered. This is the target value considered only for 1 year and not for the averaged period of 5 years.
The European Green Deal
The European Green Deal aims, among other objectives, to protect, conserve and enhance the EU's natural capital. To achieve this aim, it is essential to increase the value given to protecting and restoring natural ecosystems and biodiversity. In this context, both the Zero pollution action plan and the EU Biodiversity Strategy for 2030 want to reduce the impact of air pollution in the loss of biodiversity and in the ability of ecosystems to provide natural services.
The 8th Environment Action Plan
The 8th EAP has the long-term priority objective that by 2050 at the latest, people live well, within the planetary boundaries in a well-being economy where nothing is wasted, growth is regenerative, climate neutrality in the Union has been achieved and inequalities have been significantly reduced. A healthy environment is an environment in which biodiversity is conserved, ecosystems thrive, and nature is protected and restored, leading to increased resilience to climate change, weather- and climate-related disasters and other environmental risks.
Furthermore, it has two thematic priority objectives related to ecosystems:
1. pursuing zero pollution, and protecting the health and well-being of ecosystems from environment-related risks and negative impacts
2. protecting, preserving and restoring marine and terrestrial biodiversity by, inter alia, halting and reversing biodiversity loss and improving the state of ecosystems and their functions and the services they provide.
Related policy documents
7th Environment Action Programme DECISION No 1386/2013/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’.
8th Environment Action Programme DECISION (EU) 2022/591 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 6 April 2022 on a General Union Environment Action Programme to 2030.
The Biodiversity Strategy for 2030 COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL COMMITTEE AND THE COMMITTEE OF THE REGIONS EU Biodiversity Strategy for 2030 Bringing nature back into our lives (COM(2020) 380 final)
The Zero Pollution Action Plan COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL COMMITTEE AND THE COMMITTEE OF THE REGIONS Pathway to a Healthy Planet for All EU Action Plan: 'Towards Zero Pollution for Air, Water and Soil' (COM/2021/400 final)
The European Green Deal COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT, THE EUROPEAN COUNCIL, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL COMMITTEE AND THE COMMITTEE OF THE REGIONS The European Green Deal (COM/2019/640 final)
1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone Convention on Long-range Transboundary Air Pollution 1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone, amended on 4 May 2012.
Directive 2008/50/EC, air quality Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe.
UNECE Convention on Long-range Transboundary Air PollutionUNECE Convention on Long-range Transboundary Air Pollution.
Methodology uncertainty
This indicator provides information on the area for which monitoring data is available. In previous years, yearly changes in monitoring density influenced the total monitored area. By using interpolated maps, this problem is largely solved; maps are less sensitive for changes in the central part of the network (though more sensitive for changes in the number of stations in the outskirts).
The indicator is also subject to year-to-year fluctuations as it is mainly sensitive to episodic conditions, and these depend on particular meteorological situations, the occurrence of which varies from year to year. When averaging over Europe, this meteorologically induced variation may be less, provided spatial data coverage is sufficient. Methodology uncertainty is also given by uncertainty in mapping AOT40 based on the interpolation of point measurements at background stations. The mean interpolation uncertainty of the map of AOT40 for crops is estimated to be about 35%.
Data sets uncertainty
Most data have been officially submitted to the Commission under the Exchange of Information Decision, the Implementing Decision on exchange of information and reporting and/or to EMEP under the Air Convention. Air quality monitoring station characteristics and representativeness may not be well documented, which may imply that stations that are not representative for background conditions have been included, probably leading to a slight underestimation of the indicator. Coverage of territory and time may be incomplete.
Rationale uncertainty
This indicator is rather sensitive to the precision at the reference level (40 ppb or 80 micrograms per m3).
