Air pollution

Emissions of most air pollutants from transport in the EU-27 have fallen compared to 1990, thanks to significant policy efforts and developments in pollution control technologies. Indeed, Member States are required to meet the limits and target values for ambient air pollutant concentrations set by the Ambient Air Quality Directives (Directives 2004/107/EC, 2008/50/EC, 2015/1480/EC and COM(2022) 542). Member States are also required to achieve reduction commitments on total national emissions, set by the National Emission reduction Commitments Directive (NECD), for nitrogen oxides (NOx), sulphur dioxide (SO₂), non-methane volatile organic compounds (NMVOCs), ammonia (NH₃) and fine particulate matter (PM_2.5). While 19 Member States have met their 2020-2029 emission reduction commitments for these five main pollutants, challenges remain for NH₃. Many Member States face significant effort to meet stricter 2030 targets, especially for NOx, PM_2.5 and NH₃. A generally complex and non-linear relationship exists between direct emissions of air pollutants, their overall concentration in the atmosphere (which affects air quality) and the impact on human health.

Air pollution in Europe — 2025 reporting status under the National Emission reduction Commitments Directive

Additional information on Europe’s air quality status, how it has changed in recent decades and examples of mitigation strategies can be found, respectively, in the European Environment Agency’s ‘Air quality status report 2025’, air quality statistics and ‘Managing air quality in Europe’ products. In addition, the EEA maintains interactive maps that feature data from Europe’s air quality monitoring network.  

Despite reduced emissions and the consequent improvements in air quality over the last two decades, air pollution remains a major health concern for Europeans, according to the ‘Air quality status report 2025’. In 2023, 94% of the urban population was exposed to concentrations of PM_2.5 above the health-based guideline level set by the World Health Organization (WHO). All countries reported levels of ozone and nitrogen dioxide (pollutants linked by photochemistry) above the corresponding WHO annual guideline levels. Traffic stations accounted for around half of stations with nitrogen dioxide (NO₂) values above WHO guidance levels and two thirds of those with values above the EU annual limit. Information on the overall health impact of air pollution in Europe can be found in dedicated publications from the European Environment Agency.

The EU’s zero pollution action plan seeks to reduce the health impacts of air pollution by 55% by 2030, compared to 2005. In this context, the EC adopted the revised Ambient Air Quality Directive in October 2024 which more closely aligns air quality standards with WHO guidelines. It introduces legally binding and stricter pollutant concentration limits to be achieved by 2030; exposure reduction obligations; an expanded scope to include pollutants of emerging concern such as NH₃, black carbon (BC) and ultrafine particles; new monitoring, enforcement and public engagement requirements; and provisions for Member States to increase public information and develop air quality plans and roadmaps where exceedances occur.  

Air pollutant emissions from transport are also regulated by EU emissions standards (such as the Euro emission standards for road vehicles) and fuel quality requirements. For example, for cars, vans and heavy-duty vehicles, the recently adopted Euro 7 standard requires improvements in exhaust emissions for heavy-duty vehicles and non-exhaust emissions of all motor vehicles. Likewise, Annex VI to the MARPOL Convention of the International Maritime Organization regulates the NOx and sulphur oxides (SOx) emissions from international maritime transport. This was amended in 2025 to expand and strengthen the geographical coverage of emission control areas and tighten fuel NOx and SOx emissions requirements from ships operating in international maritime zones. Finally, the EU Sulphur Directive sets limits on the sulphur content of a range of fuels, including marine fuels.  

Despite these improvements and ongoing decarbonisation efforts, air pollution will remain a significant challenge for the transport sector. For example, non-exhaust emissions in vehicles (including electric vehicles) will remain relevant, as will emissions from currently regulated or unregulated compounds from internal combustion engines burning zero-carbon or sustainable fuels.

Evolution of main air pollutant emissions

Transport emissions of NOx decreased by 53%, SOx by 82%, NMVOCs by 90% and carbon monoxide (CO) by 90% between 1990 and 2023 (see Figure 13). As indicated in the climate section and in Figure 11, methane (CH₄) emissions fell by 75.5% during this period, while nitrous oxide (N₂O) emissions rose by 33.3% (see Figure 12). These compounds are relevant not only in the climate change context but also due to their significant contribution to air quality deterioration and depletion of the ozone layer.  

NH₃ emissions from transport activity also increased by 120% between 1990 and 2023. While globally, transport NH₃ emissions are limited compared to those from agriculture and other sectors, their impact on air quality is reported to be very high, especially within cities. This is also due to secondary aerosol formation through interactions with SOx and NOx. As discussed for N₂O in the climate section, the recent increase in NH₃ emissions (mostly in the heavy-duty sector) stems mainly from the introduction of SCR aftertreatment systems. NH₃ is used as a reducing agent in these systems to convert NOx into harmless nitrogen (N₂) and water (H₂O). NOx, NH₃ and N₂O emissions are highly interdependent in these systems and should be regulated to avoid unwanted increases in any of the three.

Recent research also indicates NH₃ emissions can be significant for modern light-duty vehicles, due to the mechanisms described above and the use of enriched air-fuel mixtures, especially at higher loads in petrol vehicles. This is done to facilitate the control of NOx, which unlike NH₃ is a regulated pollutant for these vehicles.

EU-27 transport emissions of particulate matter (PM) fell over the same time period. This includes both exhaust and non-exhaust emissions with particle diameters of 10 micrometres (µm) or less (PM₁₀) and 2.5µm or less (PM_2.5). These decreased by 47% and 59%, respectively, while BC emissions fell by 72%. Transport is also a large emitter of ultrafine particles. PM measurements hardly account for these because of their small mass, though as the largest part of the inhalable fraction of particulate matter, they are critical in terms of health impacts.

For road emissions standards, particle emissions are regulated through solid particle number (SPN) limits and measurements at type-approval and in real operation. Such measurements are not required in other transport sectors. The recently adopted Euro 7 regulation for road vehicles includes limits on non-exhaust emissions from tyres and brake wear, which are responsible for airborne PM. Studies estimate that up to 40% of emissions from brake wear are airborne.  

Between 0.2% and 22% of road vehicle tyre wearemissions are airborne, with an average of 5%. Importantly, tyre wear is considered to be a significant contributor to microplastic emissions and a source of heavy metal particle emissions. Despite the overall decrease in PM emissions, the non-exhaust fraction has increased by 63.1% from 1990 to 2023.

Uncertainties remain with the quantification of such emissions. Virtually no data are available for tyre wear from motorcycles, light commercial vehicles or heavy-duty vehicles and there is a lack of high-quality and recent data on emission factors (to mention just a few examples). A measurement procedure has been recently standardised for brake emissions. This supports the development of emission ceilings, future policy action and comparison of replacement brake components. Emission factors currently vary widely depending on test conditions.  

Figure 13 also shows transport mode trends for BC, a form of ultrafine particulate matter. BC is both a climate forcer and an air pollutant which can pose a significant threat to human health and is recognised in the 2021 WHO air quality guidelines. Evaluations suggest BC emissions were responsible for 6.85% of the maritime sector’s global warming contribution in 2018. BC is emitted through the combustion of carbon-based fuels and will therefore remain relevant even with the use of renewable or net-zero carbon fuels. 

Contribution of the transport sector to air pollution

Transport was the largest emitter of NOx in the EU-27 in 2023, with a share of 57.3%. It was also responsible for 30.9% of PM₁₀ and PM_2.5 emissions, 27.1% of BC, 22.7% of SOx, 21.3% of CO, 8.4% of NMVOCs, 5.68% of N₂O and 1.3% of NH₃ emissions. Additional information can be found in the EEA interactive data viewer, based on the inventories reported to the EEA by EU Member States under the National Emission reduction Commitments (NEC) Directive. These figures are not a direct indication of the relative importance of the transport system’s impact on air quality and human health, due to the complex and non-linear relationships discussed above. The impact of transport is high, especially in urban areas, because emissions take place close to the ground and the dilution effect is limited. For example, photochemical reactions involving NMVOCs and NOx in the presence of sunlight and hot temperatures contribute to the formation of ground-level ozone, a major component of smog that poses significant risks to human health and the environment. As population density is higher in urban areas than in rural ones, the health impacts of transport-related air pollution are also greater in urban areas.

Aviation

While aviation contributes to all pollutants considered so far, the sector is a key emitter of NOx and SOx. International aviation produced 15% of NOx emissions from transport (572Gg) in 2023 and 11% of SOx emissions.

Most air pollutant emission reductions in aviation are achieved through engine design. The application of advanced aftertreatment systems similar to those deployed in road vehicles (discussed previously) is technologically very challenging. This is mostly down to high temperatures and flow rates and the small contact areas available downstream from a conventional gas turbine.  

Ongoing research is investigating alternatives such as the inclusion of catalytic converters at the combustor level, e.g. making use of innovative catalytic or chemical methods. Another option is hybrid electric propulsion, whereby an aircraft is propelled by an electrical engine powered by electricity generated by a conventional gas turbine. Emissions from such a system could be catalytically controlled since the contact area can be increased without the loss of performance characteristic of a conventional design.

Waterborne transport

International maritime transport is the main source of SOx emissions in the transport sector and an important transport source of PM, BC and NOx. Emissions of these pollutants rose from 1990 until the mid-2000s, before falling. SOx emissions decreased the most (71%). From 2020, stricter regulation on the sulphur content of marine fuels drove SOx emissions even lower. For example, the International Maritime Organization (IMO) established the ‘global sulphur cap’ resolution MEPC.305(73), in 2020. This limits the sulphur content in marine fuel to a maximum of 0.50% mass by mass (m/m) for ships sailing in sea areas outside emission control areas (ECAs), which have a limit of 0.1% m/m. It also prohibits on-board carrying of non-compliant marine fuels for combustion purposes, i.e. for propulsion or operations on board a ship. ECAs, as defined under MARPOL Annex VI, further restrict SOx and NOx emissions in specific sea regions. There are currently two such areas in EU seas, the Baltic Sea and the North Sea (including the English Channel). The Mediterranean Sea became an ECA for SOx from 1 May 2025 under resolution MEPC.361(79).  

Maritime transport is also a significant emitter of BC, the second largest in the transport sector after road (see Figure 13). Total maritime BC emissions (including domestic and international navigation as well as international inland waterways navigation) oscillated during 1990 to 2023, peaking at 16.4Gg in 2004 (44.3% higher than 1990). Overall, emissions fell by 34% in 2023 compared with 1990. Within this sector, international navigation was the most significant contributor among those considered in Figure 13. However, the reduction in domestic emissions was very limited, reaching 2.4Gg in 2023 and representing only a 12% fall compared to 1990.