Children who grew up in London after the Ultra Low Emission Zone (Ulez) was introduced now have measurably larger and better functioning lungs than those who lived in the city before the scheme began. The finding comes from a new study that tracked thousands of primary school children across the capital, making it one of the clearest signs yet that cutting traffic pollution can directly improve young bodies.
A natural experiment in the capital
The Ulez, which charges older, more polluting vehicles to drive in central London, was expanded in 2019 and again in 2021. Researchers saw this as a rare chance to study the health effects of a real-world policy shift. They compared lung measurements from children aged 6 to 9 who attended schools inside the zone with those from children in other parts of the city, before and after the scheme was tightened.
The study, led by Queen Mary University of London, used data from more than 4,000 children. It found that children exposed to the Ulez had a 5% greater increase in lung volume and a 4% improvement in airflow, compared with children who were not exposed. The effects were strongest among children who had attended the same school for at least two years, suggesting that sustained exposure to cleaner air matters.
Why local families should care
For parents in London, the results offer a concrete answer to a question many have asked: does a clean air zone actually help my child breathe better? The answer, according to this study, is yes. The improvements were not huge, but they were consistent and statistically significant. And because lung function in childhood is a known predictor of respiratory health in adulthood, the gains could have long-term benefits.
The study's authors noted that the Ulez was not designed as a health experiment, but the data shows it has worked as one. The children who benefited were mostly from lower income families, who are more likely to live near busy roads and suffer from air pollution. That makes the finding particularly important for social equity, as cleaner air may help narrow health gaps between rich and poor.
The study was published in the journal The Lancet Planetary Health. It adds to a growing body of evidence that low emission zones, which have been introduced in cities across Europe, can have measurable health benefits. But it is one of the first to show such a clear link in children's lungs.
A breath of fresh evidence
The significance of this study goes beyond London. It provides a model for how cities can evaluate their own clean air policies. By using routine health data, researchers can track whether a scheme is working, and for whom. The findings also suggest that the benefits of Ulez may have been underestimated, because they appear in children who are still growing and developing.
No policy is without costs, and the Ulez has been controversial, with some drivers complaining about the charges. But this study offers a different kind of balance sheet: one measured in lung capacity and airflow. For the children of London, the air they breathe today is measurably better than it was before, and their bodies are showing it.
