Air pollution has significant impacts on public health. Across the UK as many as 40,000 deaths a year are attributed to outdoor air pollution, mainly from nitrogen oxides (NOX), including nitrogen dioxide (NO2), and particulates (PM10 and PM2.5). The problem is particularly acute in London, where the mortality impact of PM2.5 and NO2 pollution in 2010 was estimated at 141,000 life years lost, or the equivalent of up to 9,400 premature deaths. Air pollution is therefore the second most significant factor impacting on public health in London, after smoking.

Key findings

  • London is breaking legal and WHO limits for NO2 and WHO limits for particulate matter. Under the existing policy regime the capital is not set to reach compliance with the legal limits on NO2 until 2025 or beyond.
  • Most air pollution in London is caused by road transport, of which diesel vehicles are the most polluting. Efforts must be made to reduce the number of diesel vehicles on the road, both by increasing the proportion of cleaner and greener vehicles and by a continued shift towards alternative forms of transport, including public transport, walking and cycling.
  • It is likely that diesel cars will have to be completely phased out on London’s roads over the next decade in order to reach compliance with safe and legal levels of air pollution. Such a shift would not be easy to achieve in such a short space of time, but it would not be impossible.


New modelling undertaken by King’s College London for this project shows the scale of the changes required. Policy will be required at European, national and local levels.

European policy changes

At the European level tighter emissions standards will be required, as well as bringing forward the ‘real world’ emissions testing regime (with conformity factor 1.5 or less) which is not currently being planned until 2021.

National policy changes

At the national level, the UK government will need to progressively reform vehicle excise duty (VED) to disincentivise diesel vehicles. If it is unwilling to go far enough at the national level to drive compliance in places with acute air pollution problems like London, the government could devolve VED rates to those cities that wish to go further. Finally, to increase the pace of transition towards a diesel-free car fleet, the government could introduce a scrappage scheme for older diesel cars across the UK or in areas of non-compliance with air pollution laws.

Local policy changes

At the local level the new mayor of London, Sadiq Khan, has already indicated a willingness to take much more radical action than his predecessor. Policy measures that are likely to be needed in order to achieve compliance with legal air pollution limits include:

  • the expansion of the new ultra low emissions zone (ULEZ) across the whole of inner London; this could be progressively tightened to eventually include all diesel cars, including Euro 6
  • the progressive tightening of emissions standards within the low emissions zone (covering the whole of London) for lorries, vans, buses and taxis, with the aim of progressively phasing out diesel buses and taxis altogether
  • the introduction of new policies to promote alternative forms of sustainable transport.