Air quality in London has improved significantly since the expansion of the Ultra-Low-Emission Zone – an area within the city where polluting vehicles must pay a fee to enter.
The ULEZ was first established under current London Mayor Sadiq Khan in 2019, was expanded in 2021 and 2023, and now covers all of Greater London, where around 9 million people live. The zone is intended to reduce pollution, while the congestion charge is intended to reduce traffic (though it also reduces pollution).
The ULEZ restrictions are not all that strict: most diesel- and gasoline-powered cars made in the last 10 and 20 years, respectively, qualify, although they still emit significant tailpipe pollution. There are also exemptions for buses, delivery vehicles, and so on.
Results
Nevertheless, a recent report from the City of London shows how well the ULEZ has reduced pollution in London and improved public health. The report points out that nitrogen oxides and PM2.5, two of the most dangerous components of vehicle emissions, have dropped by almost a third compared with what would have happened without the ULEZ.
Some areas, like Central London, the most densely populated area, have seen even more significant declines – a 54% drop in NO2 levels. In ‘deprived communities,’ which tend to see the most pollution in the first place, there’s been an 80% reduction in people exposed to illegal levels of pollution. All in all, 99% of air quality monitors across London have shown a reduction in pollution, so the new rules have benefited everyone.
Children’s lungs
More information supporting the health effects of the ULEZ came out in a study this week from Queen Mary University of London. The study compared children’s lung function in London before and after the ban.
It also compared the children in London to those in Luton, a smaller, though still substantial, city just on the edge of the London metropolitan area, which is not subject to a similar low-emissions zone. Children have less-developed lungs and tend to be more affected by air pollution than adults.
Researchers recruited 3,414 children aged 6-9 before the ULEZ was introduced, 1,664 in London and 1,750 in demographically comparable Luton, which had no clean-air zone. Lung function was repeatedly measured using spirometry.
Before the zone’s implementation, children in Luton had significantly better lung function than children in London. Still, just four years after the zone was implemented, London’s children had caught up with Luton’s. Both areas saw improved lung function, but London got better, faster.
Other cities and countries
Other cities and countries have made similar moves, and each time, they seem to work quite well, resulting in less traffic, lower pollution, and easier trips. When Paris (France) kicked cars out and increased walkability and transportation options during the Olympics, the transformation received rave reviews.
Belgium actually has one of Europe’s more interesting independent LEZ evaluations. A 2025 peer-reviewed quasi-experimental study in Environment International analyzed data from 420,007 people, comparing Antwerp and Brussels with 17 Belgian control cities, as well as areas around the zones.
The study concluded that concentrations of PM2.5, PM10, NO₂, and black carbon fell significantly faster in Antwerp and Brussels than in the control cities. Importantly, there was also a ‘spillover’ benefit extending up to several kilometers beyond the zones, rather than evidence of pollution being displaced elsewhere.
However, the latest VMM (Vlaamse MilieuMaatschappij) assessment is more nuanced. In Antwerp, the agency says the LEZ has accelerated fleet renewal and caused an additional reduction in black-carbon concentrations. Still, the current LEZ has had a considerably smaller effect on NOx. Traffic still accounted for 68% of NOx emissions in 2024.
The Flemish LEZ rules have primarily removed old, soot-heavy diesels. Newer diesels admitted to the zone can still emit considerable NOx in real-world driving.
The planned tightening would have tackled this more aggressively, but it was canceled by the Flemish government in November 2025. VMM now estimates that Antwerp is unlikely to comply with the 2030 EU NO₂ limit across the board without additional measures.
In the Netherlands, there is no comparable study that directly tracks health before and after the implementation of a low-emission zone. Today’s Amsterdam passenger-car zone still only prohibits diesel Euro 4 and older.
Euro 5 diesels remain permitted, which is far less demanding than London’s ULEZ (which requires Euro 6 for diesels), and therefore helps explain the difference.
London
London now looks like one of Europe’s strongest LEZ cases, not because London invented the concept, but because the combination is unusually powerful: a huge geographical area, Euro 6 diesel requirement, 24/7 enforcement, and a £12.50 daily charge, large enough to change behavior. So it’s unsurprising to see London’s ULEZ working well, but it’s nice to have confirmation, particularly given the controversy around it at the time.
London’s ULEZ has produced measurable air-quality improvements, and there is now increasingly convincing evidence that these translate into real health benefits, particularly for children.
