Drop in Air Pollution Across Greater London as ULEZ Expansion Takes Effect

London’s air is significantly cleaner, and its residents breathe easier—thanks to the expanded Ultra Low Emission Zone (ULEZ). A newly released study confirms what advocates have long predicted: pollution levels have plummeted, particularly in the city’s most deprived areas, bringing far-reaching health benefits to millions.

The report highlights a dramatic reduction in deadly air pollutants—those linked to severe health conditions such as cancer, heart disease, impaired lung development, and even premature births. Since ULEZ’s 2023 expansion to outer London, pollution levels have fallen at an accelerated rate, surpassing improvements seen across the rest of the UK.

Despite fierce opposition, Mayor Sadiq Khan stood firm on ULEZ expansion, arguing it would drive down emissions, retire old polluting vehicles, and improve public health. As the latest findings were unveiled on Friday, he reaffirmed his stance, emphasizing that the scheme is delivering on its promises.

He 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.”

The ULEZ expansion wasn’t without controversy. Outer London councils attempted legal challenges—unsuccessfully. Meanwhile, Keir Starmer blamed the policy for Labour’s loss in the Uxbridge and Ruislip byelection, urging Khan to reconsider. However, the latest data suggests that the improvement in air quality is undeniable.

Khan said: “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.”

The report, published by the Greater London Authority and vetted by an independent panel of experts, provides the most comprehensive analysis of ULEZ’s impact. It found that outer London, in particular, has seen remarkable progress, with pollution levels aligning more closely with national averages.

Beyond improving air quality, ULEZ has also slashed carbon emissions. The report estimates that nearly 3 million one-way passenger flights between Heathrow and New York worth of CO₂ emissions have been saved. Other key findings include:

• Roadside nitrogen dioxide (NO₂) levels—a toxic gas that worsens asthma and raises lung cancer risk—have dropped 27% across London since 2019.

• PM2.5 emissions from vehicle exhausts are 31% lower in outer London in 2024 than they would have been without the 2023 expansion.

• Air quality has improved at 99% of monitoring sites across the city since ULEZ’s introduction.

Maria Neira, the director of the environment, climate change, and health at the World Health Organization (WHO), praised London’s efforts, which she said would “contribute to a healthier and more sustainable urban environment.”

She said: “Improving air quality through initiatives like Ulez 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.”

Launched in central London in 2019, ULEZ expanded across inner boroughs in 2021 before its most recent citywide enlargement in August 2023. Under its rules, the most polluting vehicles must pay a £12.50 daily charge. However, the vast majority—97% of cars—now comply and are exempt.

Before ULEZ, an estimated 4,000 premature deaths per year in London were linked to air pollution. The evidence is clear: toxic air affects every organ in the body, increasing the risk of asthma, strokes, dementia, and heart disease. However, the benefits of ULEZ are not evenly distributed—the most considerable improvements have been seen in London’s most deprived communities.

For those living near the capital’s busiest roads, exposure to illegal pollution plummeted by 80% in 2023—rising to 82% in outer London compared to a scenario without ULEZ.

Dr Gary Fuller, a clean air expert from 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.”

Simon Birkett, the director of the Clean Air in London campaign, said it was “particularly pleasing [that the report] has shown again that these big solutions work.”

He said: “In fact, together with related measures such as cleaner buses and taxis, they have almost single-handedly helped London to slash nitrogen dioxide concentrations by two-thirds near busy roads and nearly comply with legal limits and the WHO’s 2005 air quality guidelines … probably ahead of smaller UK cities.”