London’s Ultra-Low Emission Zone (ULEZ) expansionwhich came into effect across the entire Greater London area on August 29 in 2023, has significantly cut pollution levels, according to new data from TfL.
The figures show that the expansion is having a real impact on air quality, particularly in outer London boroughs, where pollution from vehicles has historically been a major issue.
In 11 outer London boroughs – Barking and Dagenham, Bexley, Bromley, Croydon, Enfield, Harrow, Havering, Hillingdon, Kingston, Merton, and Suttonthere have been noticeable reductions in harmful emissions.
Since the ULEZ expansion, nitrogen oxides (NOx) emissions have dropped by 15%, fine particulate matter (PM2.5) by 32%, and carbon dioxide (CO₂) by 1%.
What’s particularly interesting is that some of these boroughs, such as Bexley, Bromley, Harrow, and Hillingdonhad strongly opposed the expansion. They even took legal action to try and block it but were ultimately unsuccessful. Now, despite their resistance, these areas are seeing some of the biggest improvements in air quality.
Beyond just the outer boroughs, the impact of ULEZ can be seen across the entire city. The reduction in NOx emissions has contributed to an average 4.8% drop in nitrogen dioxide (NO₂) levels within the newly expanded ULEZ area. On a citywide scale, NO₂ levels are now 27% lower compared to a scenario where no ULEZ measures had been introduced.
The improvements are important because NO₂ is a dangerous pollutant linked to respiratory problems like asthma, lung infections, and even an increased risk of lung cancer. The World Health Organization (WHO) has long warned about the dangers of NO₂ and other pollutants, and London’s ULEZ is one of the biggest steps taken to tackle the issue.
Mayor Sadiq Khan has commissioned a full study to explore how and when London can meet WHO air quality guidelines for both NO₂ and PM2.5. The results of this study are expected to be published in 2025 and could influence future policies to improve air quality even further.
Some campaigners and environmental groups have been calling for stricter ULEZ rules, arguing that vehicle emission standards should be tightened to reduce pollution even more. However, Mayor Khan has said that, for now, there are “no plans” to change the existing ULEZ requirements.
One major concern he has raised is the potential expansion of Heathrow Airportparticularly the proposed third runway. He warned that if the new runway is built, it could reverse some of the air quality improvements made by ULEZ, as increased air traffic and related road congestion would likely push pollution levels back up.
As London continues to push for cleaner air, the next few years will be crucial in determining whether additional measures, such as further restrictions on high-emission vehicles or incentives for electric cars, will be needed to meet long-term environmental targets.
