Any expansion of Heathrow Airport is likely to be “undeliverable” because of associated pollution, according to a new report.
Nitrogen dioxide levels at the airport are already in breach of the EU Air Quality Directive, although management blame traffic on the M4.
Environmental experts have now concluded, in a report, that building a third runway or extending an existing one at Heathrow would delay the UK's ability to comply with NO2 limits, subjecting the government to potential fines.
The report - titled Current and Future Air Quality around Heathrow Airport – Implications for its Further Development - has been commissioned by rival Gatwick Airport and written by consultancy firm Environmental Resources Management (ERM).
The report said: “If the [Airports] Commission were to select one of the Heathrow schemes, there must be a significant risk that it may subsequently prove to be undeliverable.”
The Airports Commission has been tasked with advising the next government on whether to expand Gatwick or Heathrow in order to increase flight capacity in south-east England.
Gatwick CEO Stewart Wingate said: “The air quality around Heathrow is critical to the airport’s development plans.
“If legal standards cannot be met around Heathrow, then expansion there would be unlawful.”
Heathrow blames some of the NO2 attributed to it on traffic unrelated to the airport and says improved rail links will reduce emissions.
A spokeswoman added: “Heathrow’s expansion will only go ahead if it is meets strict environmental limits on local air quality, and with a comprehensive surface access strategy that will allow airport expansion without increasing airport related road traffic.
"We will incentivise staff and passengers to use our enhanced public transport network, that will include Crossrail, Western and Southern Rail Access and improved tube services, reduce staff car parking spaces, and look at a potential congestion charge to help reduce the number of people travelling to the airport by car.”
Gatwick says it has guaranteed not to breach EU and UK air quality limits if chosen for a second runway.
The move comes after Gatwick began distributing 400,000 leaflets across west London, outlining the noise impact that building a third runway at Heathrow would have.