People in London have been breathing significantly cleaner air since the expansion of the ultra low emission zone (Ulez), a study has found.
Levels of deadly pollutants that are linked to a wide range of health problems – from cancer to impaired lung development, heart attacks to premature births – have dropped, with some of the biggest improvements coming in the capital’s most deprived areas.
Sadiq Khan had faced severe opposition to the 2023 expansion of Ulez to outer London boroughs. But on Friday as the report was published, the mayor of London said the scheme had driven down pollution, taken old polluting cars off the roads and brought cleaner air to millions more people.
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.”
Several outer London councils mounted unsuccessful legal challenges to the Ulez rollout, and Keir Starmer blamed it for Labour’s defeat in the Ruislip and Uxbridge byelection and called for Khan to “reflect” on his plans.
But Friday’s report, published by the Greater London Authority with findings extensively reviewed by an independent advisory group of experts, said Ulez had had a positive impact and that London’s air quality had improved across the board and at a faster rate than that of the rest of the country.
The report covers the first year since the zone’s expansion and is the fullest analysis of its impact yet conducted.
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 found London’s air quality was improving at a faster rate than that of the rest of England. It said this was particularly notable in outer London, where concentrations had improved more rapidly over recent years and were now similar to the average for the rest of England.
Climate-heating gases have been substantially reduced, with carbon dioxide emissions equivalent to nearly 3m one-way passenger trips between Heathrow and New York saved.
Maria Neira, the director of 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.”
Friday’s report also found:
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Roadside nitrogen dioxide (NO2) levels, a toxic gas that exacerbates asthma, impedes lung development and raises the risk of lung cancer, have decreased by 27% across London since Ulez was introduced in 2019.
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Small-particle emissions (PM2.5) from vehicle exhausts were 31% lower in outer London in 2024 than they would have been had Ulez not been expanded in 2023.
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Air quality has improved at 99% of monitoring sites across London since 2019.
The first section of London’s Ulez scheme was launched in 2019 in the central part of the city. The zone was expanded across inner London boroughs in 2021 and enlarged again to cover the whole of the capital in August 2023.
Under the rules, the most polluting cars must normally pay a £12.50 charge each day they are driven inside the Ulez zone. A small minority of cars on the road are affected, with most petrol cars under 19 years old and diesel cars under nine years old exempt. The latest figures show 97% of vehicles in the capital are now compliant and do not pay anything.
About 4,000 premature deaths a year in London were previously attributed to air pollution. Studies show that toxic air affects every organ in the body and increases the risk of developing a wide range of health problems, from asthma to lung cancer, heart disease to strokes, cognitive development in children to dementia.
The report found some of London’s poorest communities were experiencing some of the biggest benefits. It found that for the most deprived communities living near London’s busiest roads, there was an estimated 80% reduction in people exposed to illegal levels of pollution in 2023 – this increased to 82% in outer London, compared with a scenario without the 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.”