Outdoor air quality in urban areas

Setting the scene

The 7th EAP (EU, 2013) aims to significantly improve outdoor air quality and move closer to World Health Organization (WHO) guidelines (WHO, 2006) by 2020. Air pollution is the number one environmental cause of death in the EU, responsible for more than 400 000 premature deaths per year (EEA, 2018a). According to WHO studies (WHO, 2013, 2016), exposure to particulate matter (PM) can cause or aggravate cardiovascular and lung diseases, heart attacks and arrhythmias, affect the central nervous system and the reproductive system, and cause cancer. Exposure to high ozone (O₃) concentrations can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases. Exposure to nitrogen dioxide (NO₂) worsens the symptoms of bronchitis in asthmatic children and reduces lung function growth. Health-related external costs range from EUR 330 billion to EUR 940 billion per year, depending on the valuation methodology, with evidence that the impacts of chronic ozone exposure add around 5 % to this total (EC, 2013).

Policy targets and progress

A chief cornerstone of the EU environmental acquis in the field of air quality is the Ambient Air Quality Directive (EU, 2008). This directive sets a number of air quality standards not to be exceeded by a certain year and thereafter.

The Communication on the ‘Clean Air Programme for Europe’ (EC, 2013) sets the short-term objective of achieving full compliance with existing legislation by 2020 at the latest, as well as the long-term objective of seeing no exceedances of the WHO guideline levels for human health. The key pollutants in terms of harm to human health which the Ambient Air Quality Directive addresses are particulate matter (PM₁₀ and PM_2.5), nitrogen dioxide (NO₂) and ground-level ozone (O₃) (EEA, 2016). The European air quality standards and the WHO air quality guidelines (WHO, 2006) for these pollutants are displayed in Table 1.

Table 1. Air quality standards under the EU Air Quality Directive and WHO air quality guidelines

Source: EU, 2008; WHO, 2006.

Note: 1. (*) Not considered in the indicator, where only the most stringent EU standards are used: the daily limit value for PM₁₀ and the annual limit value for NO₂. According to the WHO air quality guidelines, the annual average for PM takes precedence over the 24-hour average, since, at low levels, there is less concern about episodic excursions. 
2. In line with the Air Quality Directive: ‘limit value’ shall mean a level fixed on the basis of scientific knowledge, with the aim of avoiding, preventing or reducing harmful effects on human health and/or the environment as a whole, to be attained within a given period and not to be exceeded once attained; ‘target value’ shall mean a level fixed with the aim of avoiding, preventing or reducing harmful effects on human health and/or the environment as a whole, to be attained where possible over a given period.

Figures 1 and 2 show the percentage of the urban population exposed to air pollutant concentrations above both EU standards (Figure 1) and WHO guidelines (Figure 2).

Figure 1. EU urban population exposed to air pollutant concentrations above selected air quality standards of the EU Air Quality Directive

Figure 2. EU urban population exposed to air pollutant concentrations above WHO air quality guidelines

Around one out of eight EU citizens currently living in urban areas are exposed to air pollutant levels exceeding one or more EU air quality standards. Moreover, up to 96 % of EU urban citizens are exposed to levels of one or more air pollutants deemed damaging to health by the WHO’s more stringent guidelines (EEA, 2018b).

Particulate matter (PM)

Between 2006 and 2016, the exposure of the EU’s urban population to concentrations of fine particulate matter (PM_2.5) above the EU limit value has decreased from 16 % to 5 % (Figure 1). With respect to the more stringent WHO guideline value (Figure 2), the exposure was much larger but also decreased from 97 % to 74 %. Both percentages have been on a decreasing trend since 2011 to reach their lowest value to date in 2016.

Notwithstanding limitations in data coverage in the early 2000s, the exposure of the EU’s urban population to concentrations of dust particles (PM₁₀) above the EU limit value has decreased between 2000 and 2016 from 32 % to 13 %, with the highest value of 43 % observed in 2003 (Figure 1). For the more stringent WHO guideline value (Figure 2), the exposure was much larger but also decreased from 84 % to 42 %, with the highest value of 91 % observed in 2003. The lowest values to date were observed in both cases in 2016.

PM may be categorised as either primary (i.e. directly emitted to the atmosphere) or secondary (i.e. formed in the atmosphere from the so-called precursor gases). 

Primary PM originates from both natural and anthropogenic sources. The main emitter sector is ‘commercial, institutional and household fuel combustion’. For PM₁₀, ‘industry’ and ‘agriculture’ are in second and third place; and for PM_2.5, ‘transport’ and ‘industry’ occupy these places. All these sectors reduced their PM emissions in the EU in the 2000-2016 period, although higher relative reductions were observed for industry and transport, and only small reductions were observed for the other two sectors.

With the exception of ammonia, in the EU, reductions in emissions of the other secondary PM precursors (nitrogen oxides, sulphur oxides and non-methane volatile organic compounds) between 2000 and 2016 were much larger than reductions in emissions of primary PM.

However, reductions in both primary PM and precursors have not led to equivalent drops in the concentrations of PM. This is because chemical reactions of the precursors form secondary particles, and therefore the relationships between emissions and concentrations, are not linear. It can also be explained by uncertainties in the reported emissions of primary PM from the ‘commercial, institutional and household fuel combustion’ sector, by intercontinental transport of PM and its precursor gases from outside the EU, and by the contribution of natural sources to PM concentrations (EEA, 2016).

The contributions of the different emission sources to ambient air concentrations depend not only on the amount of pollutant emitted, but also on proximity to source, emission conditions (such as height and temperature) and other factors, such as dispersion conditions and topography. Sectors with low emission heights, such as traffic and household fuel combustion, generally make a more significant contribution to surface concentrations than emissions from high stacks.

Ozone (O₃)

Although reductions in European emissions of O₃ precursors have led to lower peak concentrations of O₃, the current target value is frequently exceeded. In the 2000-2016 period, between 8 % (in 2014) and 55 % (in 2003) of the urban population was exposed to concentrations above the target value (Figure 1), with the exposure fluctuating but not having a clear trend over time.

In relation to the more stringent WHO guideline (Figure 2), the proportion of the population exposed to concentrations above the guideline value is as high as 94-99 %, with no discernible change over time.

O₃ concentrations are determined by emissions of its precursors (mainly nitrogen oxides, non-methane volatile organic compounds and methane) and by meteorological conditions: ozone is formed in sunny conditions with high temperatures. In parallel to reductions in anthropogenic emissions of O₃ precursors, there have been increases in natural emissions and also in the intercontinental transport of O₃ and its precursors (Maas and Grennfelt, 2016). Additional factors that are also likely to mask the effects of measures taken to reduce anthropogenic emissions of O₃ precursors include climate change, emissions of non-methane volatile organic compounds from vegetation (difficult to quantify) and fire plumes from forest and other biomass fires (EEA, 2010). Formation of tropospheric ozone from increased concentrations of methane may also contribute to the sustained O₃ levels in Europe. In the EU, methane emissions from the energy and the waste sectors have been decreasing in the period 2000-2016, but much less so from the agricultural sector, which constitutes the larger emitter of methane (EEA, 2018a).   

Nitrogen dioxide (NO₂)

Between 2000 and 2016, the fraction of the urban population exposed to concentrations in excess of the EU limit value and the identical WHO guideline value gradually decreased to levels below 10 %, with a minimum of 7 % observed both in 2014 and in 2016 (Figures 1 and 2). The highest exposure of the urban population to NO₂, 31 %, occurred in 2003.

Enforcement of current legislation on emission standards for key sources of air pollution has resulted in a reduction in NO_x emissions in all sectors. Nevertheless, emissions from transport keep NO₂ concentrations high close to main roads. This is mainly due to the fact that real driving emissions are much higher than the limits set in the Euro-standards.

Overall assessment at EU level

In conclusion, for particles and nitrogen dioxide, the proportion of the urban population in the EU exposed to levels above the EU air quality standards and to the WHO guidelines has been decreasing while the trend for ozone is unclear because of the high fluctuations over time. However, because of the widespread exceedance levels in urban areas it is unlikely that the air quality standards for these pollutants will be met by 2020 across the EU, while achieving air quality in line with the WHO guidelines is much further away (except for NO₂ for which the EU standard and the WHO guidelines are the same).  

Effective air quality policies require action and cooperation at global, European, national and local levels, which must reach across most economic sectors and engage the public (EEA, 2018a). This has been recognised by the European Commission in its latest Communication ‘Clean Air for all’ (EC, 2018). Holistic solutions must be found that involve technological development, structural changes — including the optimisation of infrastructures and sustainable urban planning — and behavioural changes. These will be necessary to deliver a level of air quality across the EU that is more conducive to the protection of human health (EEA, 2016).

Country level information

Table 2 provides information on the urban population exposed to concentrations of air pollutants above the EU air quality objectives by country for 2016. Variations from country to country are not only related to the different pollutant concentrations but also, as explained in the methodology of EEA indicator ‘Exceedance of air quality standards in urban areas’ (EEA, 2018b), to:

• the number of available data series (monitoring stations and/or selected cities), which will influence the total monitored population;
• the uneven distribution of traffic and background stations in the different countries.

Table 2. Percentage of urban population exposed to concentrations of air pollutants above selected air quality standards of the Air Quality Directive, 2016

Source: Air pollution country fact sheets (EEA, 2018c). The 2016 data aggregated at EU level are also available in (EEA, 2018b and 2018d).

Note: 
1. NA = Not Available data – for further information please see indicator CSI 004.
2. NR = Not Representative – not enough number of stations to be representative.

Outlook beyond 2020

In 2013, the European Commission proposed a Clean Air Policy Package for Europe (EC, 2013), which aims to achieve full compliance with existing air quality legislation by 2020 and to further improve Europe’s air quality by 2030 and beyond. As a result of this package, the 2001 National Emission Ceilings Directive (EU, 2001) was revised in 2016. The new National Emission Ceilings Directive (EU, 2016) establishes national emission reduction commitments applicable from 2020 onwards, and stricter commitments to be achieved by 2030 onwards, for sulphur dioxide, nitrogen oxides, non-methane volatile organic compounds, ammonia and PM_2.5. In addition, and as part of the package, a new directive, the Medium Combustion Plant Directive, was approved in November 2015 (EU, 2015). This directive regulates sulphur dioxide, nitrogen oxides and dust emissions from the combustion of fuels in medium-sized combustion plants (with a rated thermal input of 1 and up to 50 megawatts). Since 2015, the Commission has also been revising the testing procedures for passenger cars and light duty vehicle emissions in view of their type-approval and placement on the market, which will ensure new vehicles' real-world emissions are in line with the existing legislation on Euro standards. The Eco-Design Directive (EU, 2009) covers residential heating appliances below 1MWth, including coal and biomass fired boilers. This will ensure that new appliances put on the market have to fulfil certain conditions to limit emissions of air pollutants; however, test procedures for those will need to be kept under control to avoid a situation, as for diesel vehicles, where test emissions and real-world emissions are in discrepancy.

These commitments made at the EU level, together with the on-going implementation of air quality measures at national, regional and local levels, are expected to improve air quality in Europe. However, the changes in meteorological conditions due to climate change are expected to increase O₃ concentrations as a result of expected increased emissions of both specific O₃ precursors and emissions from wildfires, with the latter likely to increase under periods of extensive drought (EEA, 2015).

About the indicator

This indicator shows the proportion of the EU urban population that is exposed to various potentially harmful concentrations of pollutants in excess of both the EU standards and WHO guidelines set for the protection of human health. For further information on the methodology, please refer to the EEA indicator CSI 004 ‘Exceedance of air quality standards in urban areas’ (EEA, 2018b).

The indicator focuses on those pollutants that are most relevant in terms of health effects and urban concentrations: PM, both PM₁₀ and fine PM, i.e. PM_2.5; O₃; and NO₂. When there is more than one standard, only the most stringent one is used. The indicator is based on measurements of air pollutants reported under the Air Quality Directive (EU, 2008) and the Decision on the exchange of information (EU, 2011).

Most air pollution is man-made and derives from the combustion of fossil or biomass fuels used in industry, transport and heating; industrial and agricultural processes; and other sources (EEA, 2018a). As most of these sources, particularly emissions from cars, are concentrated in urban areas where more than 70 % of the European population lives (Eurostat, 2016), air quality in urban areas is a useful proxy for tracking progress towards meeting the standards set out in the Air Quality Directive.

Footnotes and references

EC, 2013, Communication from the Commission to the Council, the European Parliament, the European Economic and Social Committee and the Committee of the Regions ‘A Clean Air Programme for Europe’ (COM(2013) 918 final).

EC, 2018, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions ‘A Europe that protects: Clean air for all’ (COM(2018) 330 final).

EEA, 2010, The European environment — state and outlook 2010, European Environment Agency. 

EEA, 2015, ‘Effects of climate change: Air pollution due to ozone and health impacts (CLIM 006)’ (http://www.eea.europa.eu/data-and-maps/indicators/air-pollution-by-ozone-2/assessment) accessed 19 April 2018.

EEA, 2016, Air quality in Europe — 2016 report, EEA Report No 28/2016, European Environment Agency.

EEA, 2018a, Air quality in Europe — 2018 report, EEA Report No 12/2018, European Environment Agency.

EEA, 2018b, ‘Exceedance of air quality standards in urban areas (CSI 004)’ (https://www.eea.europa.eu/data-and-maps/indicators/exceedance-of-air-quality-limit-3/assessment-4) accessed 17 October 2018.

EEA, 2018c, ‘Air pollution country fact sheets’ (https://www.eea.europa.eu/themes/air/country-fact-sheets)  accessed 17 October 2018. 

EEA, 2018d, ‘Air quality e-reporting database’ (https://www.eea.europa.eu/data-and-maps/data/aqereporting-8) accessed 28 May 2018.

EU, 2001, Directive 2001/81/EC of the European Parliament and of the Council of 23 October 2001 on national emission ceilings for certain atmospheric pollutants (OJ L 309, 22.11.2001, p. 22–30).

EU, 2004, Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air (OJ L 23, 26.1.2005, p. 3–16).

EU, 2008, 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 (OJ L 152, 11.6.2008, p. 1–44).

EU, 2009, Directive 2009/125/EC of the European Parliament and of the Council of 21 October 2009 establishing a framework for the setting of ecodesign requirements for energy-related products (OJ L 285, 31.10.2009, p. 10–35).

EU, 2011, Commission Implementing Decision 2011/850/EU of 12 December 2011 laying down rules for Directives 2004/107/EC and 2008/50/EC of the European Parliament and of the Council as regards the reciprocal exchange of information and reporting on ambient air (notified under document C(2011) 9068) (OJ L 335/86, 17.12.2011).

EU, 2013, 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’ (OJ L 354, 28.12.2013, p. 171–200).

EU, 2015, Directive (EU) 2015/2193 of the European Parliament and the Council of 25 November 2015 on the limitation of emissions of certain pollutants into the air from medium combustion plants (OJ L 313, 28.11.2015, p. 1–19).

EU, 2016, Directive (EU) 2016/2284 of the European Parliament and of the Council of 14 December 2016 on the reduction of national emissions of certain atmospheric pollutants, amending Directive 2003/35/EC and repealing Directive 2001/81/EC (OJ L 344/1, 17.12.2016).

Eurostat, 2016, Urban Europe—Statistics on cities, towns and suburbs — Eurostat (http://ec.europa.eu/eurostat/documents/3217494/7596823/KS-01-16-691-EN-N.pdf/0abf140c-ccc7-4a7f-b236-682effcde10f) accessed 14 June 2018.

Eurostat, 2018, ‘Life expectancy by age and sex’ (http://appsso.eurostat.ec.europa.eu/nui/show.do?dataset=demo_mlexpec&lang=en) accessed 19 April 2018.

Maas, R.,  P. Grennfelt (eds), 2016. Towards Cleaner Air. Scientific Assessment Report 2016. EMEP Steering Body and Working Group on Effects on the Convention on Long-Range Transboundary Air Pollution, Oslo. xx+50pp.

WHO, 2006, WHO air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulphur dioxide. Global update 2005, World Health Organization, Regional Office for Europe, Copenhagen.

WHO, 2013, Health risks of air pollution in Europe — HRAPIE project. New emerging risks to health from air pollution — results from the survey of experts, World Health Organization, Regional Office for Europe, Copenhagen.

WHO, 2016, ‘Ambient (outdoor) air quality and health’, Fact sheet No 313, updated March 2014, World Health Organization (http://www.who.int/mediacentre/factsheets/fs313/en/) accessed 19 April 2018.

Environmental indicator report 2018 – In support to the monitoring of the 7^th Environment Action Programme, EEA report No19/2018, European Environment Agency