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Mayor of London report: expanding Heathrow would create health costs up to £25 billion


The health-related costs from aircraft noise of an expanded Heathrow could reach £25 billion, while a third runway would risk EU legal air quality limits, according to a new Mayor of London report which sets out the scale of the challenge that the next Mayor would need to respond to if Heathrow is allowed to expand.

The report, Landing the Right Airport, focuses on the public health impacts of Heathrow expansion in addition to wider surface access and connectivity issues and the legal requirement to meet air quality limits. It argues that the next Mayor will be required to satisfy themselves that the noise, air quality and surface access challenges of a new runway can be met in the wider context of growth in London, before allowing expansion to proceed.

AEF does not support the Mayor’s proposed alternative of a new Thames Estuary Airport, as the only realistic way to meet the UK’s climate change commitments, we argue, is with a ‘no new runway’ policy (that would also rule out Gatwick). But the report provides some very useful analysis in relation to the noise and air pollution impacts of Heathrow expansion as outlined below.

Aircraft Noise

1) Even assuming that theoretical new flight paths can reduce numbers, the population exposed to noise is still huge

While the Airports Commission and Heathrow Airport assumed that flight paths could be rerouted to reduce the future population exposed, their modelling still shows at least half a million people exposed to significant aircraft noise. In addition, the Commission underplayed the noise impact of expansion, the Mayor’s report argues, by assuming an optimisation of future flight paths for reducing noise in an expansion scenario, but not in its ‘no expansion’ baseline.

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Map comparing the size of the noise contour for a two runway Heathrow (blue) with a three runway Heathrow (red). Image credit: Mayor of London. Click the image to enlarge


The Mayor of London report commissioned modelling of an alternative future baseline which assumed similar future flight paths to those assumed by the Airports Commission for a three runway Heathrow. Under this model, 46% more people would be exposed to aircraft noise above 55 dBA Lden at a three runway Heathrow than a two-runway airport, while 124 more schools and 43,200 more school-age children residents would be exposed to aircraft noise above 55 dBA Lden.

The report highlights that the Airports Commission used optimised flight paths to minimise the noise impacts for a three runway airport but didn’t use similarly optimised flight paths for comparing a future two runway Heathrow. This makes a significant difference to the forecast impact of a third runway.

Re-calculating the impact of the two runway base case, the Mayor of London report estimates that 46% more people would be affected by three runways than with two runways
(637,700 compared to 435,600). This contrasts with just 9% forecast by the Airports Commission (637,700 compared to 583,500).

2) A large number of people will be exposed to aircraft noise for the first time with a third runway

The Airports Commission’s modelling showed between 100,000 and 300,000 people would be exposed to significant aircraft noise for the first time with a third runway. Under the flight path scenario aimed at reducing the total number of people exposed to aircraft noise, 43% of the total number exposed are newly exposed. Even the Commission’s scenario which aims to reduce the numbers newly affected exposes around 100,000 people to noise at 55 dBA Lden for the first time, which the Mayor’s report highlights is larger than the total numbers affected at Manchester Airport, the second noisiest airport in the UK.

The question of whether it is acceptable to expose new populations to aircraft noise from changes to flight paths is one that the Government is expected to consider when it looks into possible changes to its airspace policy this year.

3) A partial night flights ban would actually mean more night flights

The report identifies that the Airports Commission’s proposed night flights ‘ban’ from 11:30 till 6 a.m. would lead to 32% more flights, compared to today, in the night period as defined by the WHO, EU and UK Government, namely 11pm to 7am. AEF’s aircraft noise and health report highlighted that the Airports Commission’s own analysis showed that the health benefits of a full night flights ban would be far greater than those associated with the proposed ban.

Comparing the number of night flights today with a third runway. Credit: Mayor of London


4) A high health cost of aircraft noise

The Mayor of London report applies the Department for Transport’s new WebTAG methodology to assess the health costs of aircraft noise, which AEF used in its aircraft noise and health report, and provides a monetary value for increased risk of heart attack, stroke, dementia alongside sleep disturbance and the health costs of annoyance. The Mayor of London report estimates the harm of an expanded Heathrow to be valued at £20-25bn over 60 years, with £6.24bn related to the third runway. This compares to the Airports Commission’s estimated economic cost of noise of £1.55bn used in the cost-benefit analysis of a third runway under a carbon traded scenario. The difference in estimated costs of £4.7bn represents 40% of the entire claimed net economic benefit. Under a carbon capped scenario the impact is negative.

Air quality

The Mayor of London report also considered the Airports Commission’s air quality assessment. It identified that additional airport specific emissions from aircraft and airport vehicles could increase concentrations of NO2 by up to 4-8μg/m³ ­–  equivalent to 10-20% of the EU limits – and that some of the measures proposed to manage noise impacts would require greater engine thrust and could therefore increase aircraft emissions. In addition, the report highlights an expanded Heathrow would increase airport and non-airport related traffic as a result of the additional passengers and freight and inducing wider traffic flows.

The report then assesses the air quality impact of expansion if the Government’s proposed air quality action plan – published several months after the Airports Commission’s final report – is delivered by 2030. Under the new plan, the Bath Road link (where, the Airports Commission found, NO2 could be the highest in the UK with Heathrow expansion), would be within 10% of EU limit values if the Government’s air quality action plan is fully implemented without a new runway.

Under the updated Government modelling, the entire Greater London area would be compliant with the legal limit by 2030. The Mayor’s report argues that with expansion, locations on the Bath Road near the third runway could witness increases of between 4 and 8μg/m³ NO2, pushing concentrations above 40μg/m3 and so rendering the Greater London zone non-compliant.

The Parliamentary Environmental Audit Committee recommended last year that Heathrow expansion should be conditional on the Government demonstrating that it would be compatible with EU air quality limits.

The Government postponed a decision on Heathrow expansion in order to complete additional environmental assessments last December and the Mayor of London report has exposed further limitations in the Airports Commission’s work.


Mayor of London report: Landing the Right Airport 

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