Air quality improves across London following ULEZ expansion

London’s City Hall has published evidence showing measurable improvements in the capital’s air quality following the first year of the expanded Ultra Low Emission Zone (ULEZ).

In April 2019, the Mayor of London launched the world’s first 24-hour Ultra Low Emission Zone (ULEZ) in central London. The zone was expanded across inner London in 2021, and all London boroughs In August 2023.

The peer reviewed analysis shows air quality has improved at 99% of monitoring sites across London since 2019 and with the full ULEZ expansion, London’s air quality is now improving at a faster rate than the rest of England. Around 4,000 premature deaths per year in the capital were previously attributed to toxic air.

Notably roadside Nitrogen Dioxide (NO2) levels, a toxic gas that exacerbates asthma, impedes lung development, and raises the risk of lung cancer, have decreased by a record 27% across the entire capital. While the biggest reductions in NO2 levels have been in central London (54%), there have also been substantial reductions in inner London (29%) and outer London (24%)

Particle emissions (PM 2.5) from vehicle exhausts, are 31% lower in outer London in 2024 than they would have been without the ULEZ expansion.

The reduction in carbon emissions has also been substantial, equivalent to nearly three million one-way passenger trips between Heathrow and New York saved. Data from the report indicates that the ULEZ expansion has not impacted footfall or retail and leisure spending in either outer London or London as a whole.

The Mayor of London, Sadiq Khan, said, “When I was first elected, evidence showed it would take 193 years to bring London's air pollution within legal limits if the current efforts continued. However, due to our transformative policies we are now close to achieving it this year. This report shows that ULEZ works, driving down levels of pollution, taking old polluting cars off our roads and bringing cleaner air to millions more Londoners.

“The decision to expand the ULEZ was not something I took lightly, but this report shows it was the right one for the health of all Londoners. It has been crucial to protect the health of Londoners, support children's lung growth, and reduce the risk of people developing asthma, lung cancer and a host of other health issues related to air pollution.  

TfL data also shows that Londoners have upgraded their vehicles to cleaner models with 97% of vehicles seen driving in London now ULEZ compliant, up from 92% in June 2023 and 39% in February 2017, when changes associated with the ULEZ began. Van compliance in outer London is over 90% for the first time. In February 2017, just 12% of vans met the ULEZ standards, demonstrating the schemes’ impact on reducing the number of more polluting older vans driving in London.

Dr Maria Neira, Director, Department of Environment, Climate Change and Health at the World Health Organization said, "Improving air quality through initiatives like the Ultra Low Emission Zone in London is crucial for protecting public health and reducing the burden of disease. Cleaner air leads to healthier communities, lower rates of respiratory and cardiovascular illnesses, and a better quality of life for all residents. The World Health Organization commends the efforts of cities like London in implementing measures to reduce emissions from vehicles and improve air quality, which ultimately contribute to a healthier and more sustainable urban environment."

Anne Hidalgo, Mayor of Paris, said, “Reducing car traffic is one of our greatest opportunities to address the climate emergency. Under the leadership of Mayor Khan, London is showing us what safer, healthier, and greener communities look like, and the results of London's clean air zone speaks for itself. I commend Mayor Khan for his commitment, leadership and vision to addressing the climate crisis and protecting the lives and health of city residents. London is demonstrating once again that cities lead the fight against climate change.”

Christina Calderato, TfL’s Director of Strategy, said, “Bold and ambitious environmental schemes like the ULEZ are pivotal to making tangible long-term air quality improvements to tackle a public health crisis, as shown in this new report. Everyone in the capital is now breathing cleaner air because of ULEZ.

“It is great to see it making a real difference to the air Londoners breathe, and together with our efforts to decarbonise the public transport network, will see generations to come reaping the benefits of a greener, cleaner London.”

Dr Gary Fuller, Imperial College London, and Chair of the ULEZ Advisory Group, said, “Each phase of the ULEZ has led to clear improvements in the air pollution next to London’s roads. This is good news for the current and future health of Londoners, as well as those who travel to London for work or leisure.  

“The analysis in this report benefited from an international advisory group of scientists, all with experience in assessing the impacts of urban clean air policies. We worked with the Mayor’s team to stress-test key parts of the analysis and concluded that the core methodology used in this report, and in previous ULEZ reports, was appropriate and robust. The ULEZ is one of over 300 such schemes across the UK and Europe, and many cities are looking to London's ULEZ results to inform their own plan.”