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Local Air Quality

In terms of public perception, local air quality rates a poor third in the list of impacts that airports have on the environment: most complaints are in respect of noise, while the greatest strategic concern is aviation’s contribution to global climate change.  Nevertheless, the control of local air quality can be a legal constraint to the growth of airports and may be of some relevance to the health of people living nearby.  The odors generated by aircraft (e.g. kerosene vapor or tire smoke) may also be a local nuisance.


Air quality was a key issue for the proposed third runway at Heathrow.  The EU limit value for long-term NO2 concentrations in the public environment is 40 μg m-3; measured concentrations at some sites around Heathrow already exceed 50 μg m-3.  Given this situation, it was clearly difficult to justify an extra runway.  Most of the public opposition to the extension arose from concerns about noise, demolition of homes etc., but the EU air quality standards represented a hard legal constraint that would have led to any planning consent being called in for judicial review.  Predictions of the impact of the new runway depended critically upon numerical modeling of pollution emission dispersion; CATE was deeply involved in this process.


As it happens, the EU limit on NO2 is probably unrealistically low: the equivalent limit in the US is 100 μg m-3.  In effect, NO2 is being used as a surrogate for general air quality, and it is incontrovertible that poor air quality, particularly in the form of fine urban aerosol (PM2.5), is still killing our fellow-citizens in large numbers.  The current PM2.5 concentrations around Heathrow are only ~15 μg m-3 – well within current regulatory guidelines and substantially less than near busy roads in central London.   Nevertheless, epidemiological studies suggest that an extra 10 μg PM2.5 m-3, can increase general urban mortality by ~16%, this corresponding to a reduction in life expectancy of ~2 years.  We should be very careful, however, in assuming that the urban PM2.5 from the epidemiological studies is equivalent to that around an airport.  Not all fine aerosol is the same – particles can vary by size, shape, composition and toxicity – and CATE has worked on the characterization of some of the aviation-related sources, in particular tyre smoke and engine emissions.


CATE has the use of a substantial range of experimental methods to characterize emissions and their dispersion in the atmosphere.  We also have experience in the use of regulatory dispersion models (ADMS, LASPORT).

Research Studies

Clearly, a robust understanding of the factors underlying local air quality is essential if airports are to be further developed, or if their existing impact is to be abated.  CATE has been involved in a number of projects on both of these aspects:

  •  Air Quality in Airport Approaches: Impact of Emissions from Aircraft in Ground Run and Flight (2004 – 2007) This project involved a series of field campaigns at Heathrow and Manchester airports, principally using the scanning Lidar, to characterize the dispersion of the exhaust emissions from commercial aircraft.         These measurements were then used to develop a numerical model of aircraft plume dispersion. EPSRC grant reference EC/C514920/1; also some DfT and European Commission funding.


  • Aviation Emissions and their Impact on Air Quality (2007-2009) This project, undertaken in collaboration with the FAAM aircraft at Cranfield (FAAM) and with groups from Cambridge, Reading, Oxford and Leeds, extended over four field trials.  The work was used to develop a range of novel technologies to characterize the atmospheric emissions from the aircraft (NO2/NOx ratios in the exhaust gases; composition of tyre smoke). Omega grant.
  • A Study of Practical Abatement Techniques for Exhaust Jets from Commercial Aircraft (2009-2012) This study uses the theoretical understanding of dispersion gained in the earlier trials to develop a system to abate the local environmental impact of exhaust emissions.   By making the field surface aerodynamically rough, we can encourage the emissions to rise buoyantly away from the ground.  EPSRC grant reference EP/H002987/1


  • Impact of Airspace Closure on Local Air Quality at Airports  (2010) In April 2010, the eruption of Eyjafjallajökull led to European airspace being closed for several days.  This provided a unique opportunity to test the predictions of the regulatory dispersion models.  A statistical analysis demonstrated the impact of the airport on NO2 concentrations at Heathrow and Schiphol.  Funded by Aeronet.


Bennett M and Christie S (2006) ‘Optical measurements of pollution dispersion at commercial airports’, Photon06, Manchester, 4-7 September 2006.

Bennett M and Christie S (2007) ‘An application of backscatter Lidar to model the odour nuisance arising from aircraft tyre smoke.’ Proc. 11th Int. Conf. on Harmonization within Atmospheric Dispersion Modeling for Regulatory Purposes. Cambridge, UK,  2-5 July 2007

Bennett M, Christie S, Graham A and Raper D (2010) ‘Lidar observations of aircraft exhaust plumes’, J. Atmospheric and Oceanic Technology, 10, 1638-1651.  Available online at

Bennett M and Christie S (2011) ‘An application of backscatter Lidar to model the odour nuisance arising from aircraft tyre smoke’, Int. J. Environ. & Poll., 44, 316-328.

Bennett M, Christie SM, Graham A, Thomas B S, Vishnyakov V, Morris K, Peters D M,  Jones R and Ansell C (2011) ‘The composition of tyre smoke from landing aircraft’, Environ. Sci & Technol.

Bennett M and Hoolhorst A (2010) ‘Control of Local Air Quality at European Airports’, Report to European Commission, ECATS/D5000.02.365.

Bennett M and Raper D (2010) ‘Impact of airports on local air quality’, in Encyclopedia of Aerospace Engineering, R Blockley and W Shyy (eds). John Wiley & Sons Ltd., 3661-3670. DOI: 10.1002/9780470686652.eae350

Christie S, Bennett M, Graham A and Raper D W (2006) ‘Lidar monitoring of aircraft emissions for environmental air quality’, Photon06, Manchester, 4-7 September 2006.

Cruz-Jimate I and Bennett M (2006) ‘Application of a FTUV system to measure ambient pollution in central Manchester and at Manchester Airport’, Photon06, Manchester, 4-7 September 2006.

Graham A and Bennett M (2011) ‘Buoyant release from an accelerating ground source. Part I: Theory’, Submitted to  Environ. Fluid Mech.

Graham A, Bennett M, Christie S and Raper D (2011) ‘Buoyant release from an accelerating ground source. Part II: Application to aircraft in takeoff’, Submitted to Environ. Fluid Mech.

Graham A, Bennett M and Christie S (2008) ‘Representing the dispersion of emissions from aircraft on runways’, Proc. 12th Int. Conf. on Harmonization within Atmospheric Dispersion Modelling for Regulatory Purposes. Cavtat, Croatia,  6-9 October 2008.

Graham A, Raper D W, Christie S and Bennett M (2005) Lidar Study Report, ‘Air quality at Heathrow Airport: impact of emissions from aircraft in ground run and flight’. Annex 7 (pp. 312-332) of  Project for the Sustainable Development of Heathrow: Air Quality Technical Report. Department for Transport. (December 2005)