In the third and final instalment of our aviation and carbon series, we’re focusing on air pollution emissions in and around the vicinity of airports.

We’re also highlighting actions that must be undertaken to dramatically reduce airport-attributed toxins in our air – not only for airport users, but for those who live, work and travel nearby.

Nitrogen dioxide (NO2) and particulate matter (PM₁₀) are the key aviation-related air pollutants. Such is the concern about the damage these toxins are causing to human health in and around many UK airports, that an air quality objective has been set within the Air Quality Standards Regulations (2010).

Where these air quality objectives are exceeded, an air quality management area (AQMA) can be declared by the relevant local authority, and over 700 AQMAs have already been declared due to exceedances of the annual mean air quality objective for NO2. Perhaps unsurprisingly, Heathrow and Gatwick airports are both located near AQMAs and like so many other airports, contribute pollutants towards them via traffic and of course airport emissions.

Capita is the UKs leading authority on clean air zones, having already reduced NO2 levels in London’s ULEZ by 44%. We’ve taken our expertise in this area and have crafted a suite of solutions for aviation. There are of course multiple airport activities that directly contribute to the air quality of the airport vicinity and an AQMA. To improve the air quality in and around an airport, we must first identify the contributions of all emissions sources to effectively and efficiently mitigate against them.

Establishing a suitable air quality monitoring network is therefore crucial, not only in determining whether air quality objectives are being met, but also to uncover major sources of emissions and any seasonal or temporal trends. Capita can devise a monitoring strategy to fulfil these baseline objectives, which may unearth the need for other requirements, such as:

  • A source apportionment study - which analyses main emission sources to identify and apportion air pollution contributors. 
  • An emission inventory study - where information on air emissions sources is collated to estimate emission rates which can be used within a detailed model. Emission factors can be derived from aircraft engine specifications, or where this is not available, can be estimated based on fuel usage. An emission inventory study includes sources ranging from stationary (power plants, boilers, generators) to mobile sources (aircraft auxiliary power units emissions during idle, approach, climb out and take off, aircraft fuelling, aircraft ground handling and traffic etc.) and takes flight timetables into account.
  • A detailed dispersion modelling exercise – this takes account of all the identified emission sources to predict concentrations associated with the airport.
  • A model verification exercise - to ensure the detailed dispersion results correlate with concentrations observed at the monitoring location (established as part of the overall monitoring strategy).  
  • Mitigation measures - we’ll propose mitigation measures based on the data from the detailed modelling exercise (including source apportionment, emissions inventories and predicted concentrations). 
  • An options appraisal study - Using the latest modelling software, we can provide advice on the various mitigation options, and estimate levels of improvement for implementing each option.
  • An air quality action plan - a bespoke airport plan highlighting how specific measures could be implemented, and details of how any further measures to improve air quality could be developed.

Without doubt, the levels of toxic air in the vicinity of UK airports don’t just suggest, but shout out the need for urgent and decisive action. Our expertise in clean air – whether in our cities or AQMAs, ensures that airports can rely on us to create and deliver a roadmap for dramatic and clear improvements to their users, as well as those who live, work, and travel nearby.

Augmenting governmental pressures and industrial regulations, combined with ever-increasing environmental concerns from consumers, mean those airports which take action now will have a fighting chance of remaining operational and relevant as we step out of the pandemic crisis, and enter the next phase of aviation travel.

Written by


Dr Xiangyu Sheng

Director of Climate Change and Air Quality, GL Hearn (part of Capita Plc)

Dr Sheng is leading our air quality and climate change team to provide solutions to the most complex challenges. She has over 25 years' experience and is a Fellow of the Meteorological Society (FRMets), a Chartered Engineer (CEng), a Chartered Physicist (CPhys), a Chartered Scientist (CSci) and a Chartered Environmentalist (CEnv).


Ruairi Martin BEng (Hons) DIS CEng MIStructE

Aviation Director, Capita Real Estate and Infrastructure

As Aviation Director for Capita Real Estate and Infrastructure and a Chartered Structural Engineer, Ruairi is passionate about promoting our expertise to the Aviation Industry, both nationally and globally and in using cross sector innovation to provide environmentally sustainable solutions. Ruairi has over 30 years experience in the construction industry and has involved in major projects in the Middle East, Asia Pacific and South America as well as in the UK and Europe.

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