Key information
Request reference number: MGLA040322-6005
Date of response:
Summary of request
Your request
Air pollution levels in London prior to the new Ultra Low Emission Zone (ULEZ) charges, and what they are now.
Our response
Concentrations of air pollutants are significantly affected by a range of factors, particularly the impact of weather, natural seasonal variations and, for nitrogen dioxide (NO2) significant atmospheric chemistry processes involving other pollutants and sunlight. It is also the case that legal limits are set on the basis of annual mean concentrations over the calendar year. For these reasons we have not yet published detailed analyses of the impact of the ULEZ expansion on air pollution.
In December 2021 we published a report on the first month of operation of the scheme. This report focused primarily on vehicle compliance, as this can be robustly measured early on. The report found that compliance was around 92%, substantially up from the baseline of 37% in 2017. This is an early indicator that the scheme is likely to be successful in reducing pollution.
We will follow this up with reports after 6 months and 12 months of operation of the scheme. Each of these reports will be able to provide more detailed analysis of key air pollution metrics such as emissions and concentrations of pollutants.
We have published more detailed analysis of the impacts in central London of the earlier iteration of the ULEZ. This analysis found that between February 2017 and February 2020, there was a 39 micrograms per cubic metre reduction in roadside concentrations of NO2 in the central zone, a reduction of 44%, as well as a 27% reduction in Particulate Matter (PM2.5). You can read the full report here.
There is also a wide range of air pollution data that is available publicly, and I have provided some links and a description of the key information sources below.
Concentrations of air pollutants are most accurately monitored by the London boroughs, with additional monitoring provided by Transport for London, the Environment Agency and others. Data from these automatic monitors, both live data and archived historical data, can be accessed here.
In addition to this monitoring the GLA supports the Breathe London project, which uses low costs sensors to monitor air pollution at a higher spatial resolution. As the Breathe London pods are still being installed, they may not cover the full period you are interested in.
These data sources provide access to the raw data, for a bit more context the London Air Quality Network (run independently by Imperial College, on behalf of some of the London boroughs), has some helpful resources.
If you have any further questions relating to this matter, please contact us, quoting reference MGLA040322-6005.