EIR - Heathrow third runway [Aug 2026]

I am writing to seek clarification regarding what appears to be an important public-policy question concerning the relationship between London's environmental objectives and the Government's proposal to expand Heathrow Airport.

London residents and businesses are required to comply with measures such as the Ultra Low Emission Zone and the Congestion Charge, both of which are presented as contributing to improved air quality, reduced pollution and the protection of public health.

At the same time, the Government is consulting on proposals to expand Heathrow Airport through a third runway, increasing aircraft movements and the associated emissions from aviation.

I would therefore be grateful if you could clarify the following questions.

1. How are London's environmental and public-health objectives reconciled with proposals to increase aircraft movements at Heathrow?
2. Has the Greater London Authority undertaken any assessment comparing the objectives of London's air-quality policies with the anticipated effects of Heathrow expansion?
3. If aviation emissions remain outside the Mayor's direct regulatory powers, has the Greater London Authority formally raised concerns with the Government regarding the consistency of these two policy approaches?
4. Has any assessment been undertaken of the cumulative effect of increased aviation emissions, including nitrogen oxides and particulate pollution, on London residents living beneath Heathrow's flight paths?
5. Has any assessment considered the potential long-term public-health implications of prolonged exposure to increased aviation emissions, including respiratory diseases such as chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis where relevant?
6. If London asks residents and businesses to reduce pollution through local environmental measures, what equivalent environmental accountability applies to increased aviation activity?
7. Has the Greater London Authority received evidence from the Government demonstrating that Heathrow expansion is consistent with London's wider environmental and public-health objectives?
8. If such evidence exists, is it publicly available?
9. Has the Greater London Authority assessed whether Heathrow expansion could undermine the environmental improvements sought through London's clean-air policies?
10. Has any assessment been made of the long-term costs to London's health services and local authorities arising from additional aircraft movements?
11. How has the impact on communities already affected by aircraft noise and air pollution been balanced against the projected economic benefits of expansion?
12. Does the Greater London Authority consider that the Heathrow consultation sufficiently addresses the relationship between London's environmental policies and national aviation policy?
13. If not, what further assessment or clarification does the Greater London Authority believe should be undertaken before any final decision is made?

Our response

Although we have handled your request under the provisions of the Freedom of Information Act, Some of your questions are invalid for this purpose because your question is seeking an opinion/explanation of a word rather than a request for recorded information held by the GLA. However, under our duty to advise and assist, we have attempted to provide a response to questions 6, 11and 13.

The Mayor has been clear in his opposition to a third runway at Heathrow, based on the severe impact it would have on noise, air pollution and our ability to meet climate change targets. He is also concerned about the significant knock-on effects that Heathrow expansion would have on London’s transport infrastructure.

The Department for Transport is currently consulting on a draft Heathrow Expansion National Policy Statement (HENPS), which sets out the objectives the Heathrow expansion should seek to achieve and the criteria that promoters would need to meet in order for a planning application to be approved, including on air quality, noise and carbon emissions. The Mayor will be responding to this consultation in due course to make his views clear.

1. How are London's environmental and public-health objectives reconciled with proposals to increase aircraft movements at Heathrow?

The Mayor's environmental policies, including measures such as the Ultra Low Emission Zone (ULEZ), seek to reduce harmful emissions from sources within the Mayor's powers and improve air quality and public health in London. Decisions relating to airport expansion and aviation policy are primarily matters for Government and the relevant planning processes. Any proposal to expand Heathrow would need to be assessed against applicable legal and policy requirements, including environmental, air quality, climate change and public health considerations.

2. Has the Greater London Authority undertaken any assessment comparing the objectives of London's air-quality policies with the anticipated effects of Heathrow expansion?

The GLA has previously reviewed and responded to proposals relating to Heathrow expansion and has considered issues including air quality, climate change and surface transport impacts. The GLA does not hold a single assessment specifically framed as a comparison between London's air-quality policies and Heathrow expansion.

3. If aviation emissions remain outside the Mayor's direct regulatory powers, has the Greater London Authority formally raised concerns with the Government regarding the consistency of these two policy approaches?

The Mayor has, on a number of occasions, expressed concerns regarding the environmental and climate impacts associated with Heathrow expansion. These concerns have formed part of representations made through consultation and planning processes.

4. Has any assessment been undertaken of the cumulative effect of increased aviation emissions, including nitrogen oxides and particulate pollution, on London residents living beneath Heathrow's flight paths?

Environmental assessments associated with Heathrow expansion proposals have included consideration of air quality impacts, including emissions of nitrogen oxides and particulate matter. Detailed assessment of these impacts forms part of the statutory processes led by Heathrow Airport Limited and are examined by relevant decision makers.

5. Has any assessment considered the potential long-term public-health implications of prolonged exposure to increased aviation emissions, including respiratory diseases such as COPD and pulmonary fibrosis where relevant?

The GLA is aware that public health impacts associated with air pollution are considered within environmental and health evidence used in airport expansion assessments. The GLA does not hold a specific assessment focused solely on the long-term incidence of particular diseases arising from Heathrow expansion.

6. If London asks residents and businesses to reduce pollution through local environmental measures, what equivalent environmental accountability applies to increased aviation activity?

Aviation activity is subject to a separate regulatory framework set by Government and the Civil Aviation Authority, including environmental assessment requirements, planning controls, aviation regulation and relevant national carbon and air-quality obligations.

7. Has the Greater London Authority received evidence from the Government demonstrating that Heathrow expansion is consistent with London's wider environmental and public-health objectives?

GLA does not hold a document specifically designated as evidence from Government demonstrating consistency with all of London's environmental and public health objectives.

8. If such evidence exists, is it publicly available?

Information relating to Heathrow expansion has generally been published through Government consultations, planning documentation and associated environmental assessments. Relevant documents can be found through Government and Heathrow Airport consultation and planning websites.

9. Has the Greater London Authority assessed whether Heathrow expansion could undermine the environmental improvements sought through London's clean-air policies?

The GLA has previously considered the potential implications of Heathrow expansion for air quality, climate change and related environmental objectives. Concerns regarding potential impacts on environmental outcomes have been raised during previous consideration of expansion proposals.

10. Has any assessment been made of the long-term costs to London's health services and local authorities arising from additional aircraft movements?

The GLA does not hold a specific assessment quantifying the long-term costs to health services and local authorities arising from additional aircraft movements associated with Heathrow expansion.

11. How has the impact on communities already affected by aircraft noise and air pollution been balanced against the projected economic benefits of expansion?

This consideration forms part of the Government's decision-making and planning processes for nationally significant infrastructure projects. Relevant decision makers are required to consider economic, environmental, health and community impacts when assessing such proposals. The Mayor has been clear that he does not believe Heathrow expansion can be delivered without serious negative impacts including related to air pollution and noise.

12. Does the Greater London Authority consider that the Heathrow consultation sufficiently addresses the relationship between London's environmental policies and national aviation policy?

The Mayor's previous responses concerning Heathrow expansion have highlighted the importance of ensuring that national aviation policy is compatible with air quality, environmental and climate objectives.

13. If not, what further assessment or clarification does the Greater London Authority believe should be undertaken before any final decision is made?

Any major infrastructure proposal should be supported by robust evidence on its environmental, public health, climate and community impacts, and the Mayor would expect decision makers to consider such evidence before reaching a final decision.

For more detail on the Mayor’s view on the latest Heathrow expansion proposals, see the Mayor of London and Transport for London’s submission to the current Transport Select Committee inquiry on the draft Heathrow Expansion National Policy Statement. This can be found under the Written Evidence section of the Committee’s website: https://committees.parliament.uk/work/9865/scrutiny-of-the-draft-heathrow-expansion-national-policy-statement/publications/written-evidence/?page=4.