A robust scientific understanding of the environmental impacts from aviation is an essential basis for informed policy discussions, and for the development of effective mitigation measures that achieve the desired outcome in a cost-effective way. This chapter provides an overview of the latest scientific understanding on the noise, air quality and climate change impacts from the aviation sector.
Air pollution has significant impacts on the health of the European population, particularly in urban areas. The most significant pollutants in terms of harm to human health are particulate matter (PM), nitrogen dioxide (NO2) and groundlevel ozone (O3).
Aviation and air pollution
Air quality in the vicinity of airports is not just influenced by the emissions from aircraft engines, but also from other sources such as ground operations, surface access road transport and airport on-site energy generation and heating 21 and ground-level ozone.. The most significant emissions related to health impacts from aviation activities are particulate matter (PM), nitrogen oxides (NOX) and volatile organic compounds (VOCs). Some of these primary pollutants undergo chemical and physical transformations in the atmosphere that in turn produce other pollutants such as secondary particulate matter
Nitrogen oxides (NOX)
NOX emissions are primarily produced by the combustion of fossil fuels, especially at high temperatures such as those experienced in aircraft engine combustors. In the atmosphere, nitrogen monoxide (NO) is rapidly oxidised to nitrogen dioxide (NO2), which is associated with adverse effects on human health such as lung inflammation. NO2 also plays a key role in the formation of secondary particles and ground-level ozone. Thus, nitrogen oxides have both a direct and an indirect impact on air quality.
Particulate matter (PM)
Particulate matter is a general term used to describe very small solid or liquid particles. Emissions from aviation related activities, in a similar manner to other sources using carbon-based fuels, contain PM10 and PM2.5 emissions22, as well as ultrafine particles (PM1, PM0.1) that have very small diameters . Such small particles, irrespective of the combustion source, can deposit in the human lung, pass natural barriers in human cells and enter the bloodstream. Solid ultrafine particles can trigger inflammation and act as carriers for toxic substances that damage the genetic information in cells. The EU Ambient Air Quality Directives contain regulatory limits for PM10 and PM2.5 in ambient air, but not for ultrafine particles. However, PM2.5 is considered to be a good indicator of general risk associated with exposure to particulate matter. As the mass of the ultrafine particle emissions is so low, measurements of aircraft engine emissions have also focused on the number of emitted particles.
The presence of ozone in the high-altitude stratosphere provides an essential natural shield against harmful ultraviolet radiation from the sun. However, ground-level ozone can cause several respiratory problems, including reduced lung function, bronchitis, emphysema and asthma.
Evaluating the impact of aviation emissions
Most evaluations of air quality impacts from aviation have focused on the health impacts of PM2.5 formation attributable to aviation, with some others including the impact of ozone as well. Some studies, have focused on landing and take-off emissions, as these happen at relatively low altitudes and therefore closest to local populations. A limited number of studies , have also attempted to evaluate the impact of aviation emissions on human health at a global scale by including aircraft emissions at high altitude.
21 Secondary particulate matter is formed from chemical reactions in the atmosphere from the gases ammonia (NH3), sulphur dioxide (SO2) and nitrogen oxides (NOx), and from organic compounds.
22 The subscript ’10’ in PM10 refers to particles with a diameter of less than 10 microns (0.01 millimetres).