London Children's Lungs Are Growing Faster Since the Ultra Low Emission Zone Began

London children's lungs are catching up. A five-year study of 3,414 children aged six to nine has found that their lung capacity grew roughly 10 millilitres per year faster than children in Luton, a nearby town without a clean air zone.

That figure is an association, not a lab measurement of cause and effect. Researchers built the comparison as a "natural experiment" — testing what happens to children's bodies when a government changes the air around them, rather than modelling the effect in a laboratory — the University of Oxford, which co-led the project, said in its August 19, 2026 summary.

A study built to test one question

The research, known as the CHILL study, tracked children from 84 primary schools before and after London's Ultra Low Emission Zone took effect in 2019, comparing them against children in Luton, a town chosen because it had no equivalent low-emission scheme.

Before the zone was introduced, children in central London had measurably smaller lungs than their peers in Luton, according to Oxford's summary. Nitrogen dioxide, the pollutant most closely tied to traffic exhaust, fell by approximately 22% in London between 2018 and 2022, according to data cited in a BMJ report published August 19, 2026. That report did not specify whether the reduction was measured at roadside monitors or through modelled personal exposure — a distinction that matters for comparing it directly with Luton. The National Institute for Health and Care Research reported the same day that NO2 exposure in London fell twice as fast, and more than twice as much, as it did in Luton over the same period.

The gap that disappeared

At the study's outset, London children were measured with a -38 milliliter gap in forced expiratory volume in one second, or FEV1 — the standard spirometry measure of how much air a person can forcefully exhale — compared with children in Luton. An analysis published by AJMC (The American Journal of Managed Care) on August 20, 2026, which included 3,209 children with at least one FEV1 measurement, found that gap closed entirely within four years of the zone's introduction.

Queen Mary University of London's own summary of the same project dates the closure differently, saying the gap had "effectively disappeared" only by the end of the full five-year study. The two accounts do not agree on when the recovery was complete, and neither institution's published material reconciles the difference.

The shift also shows up in a separate measure of impairment. The proportion of London children with clinically impaired lung function fell from 14% to 9% over the five years, the NIHR reported on August 19, 2026. Luton's control group saw a smaller decline, from 9% to 7%, over the same period.

What researchers are saying

Professor Chris Griffiths, a joint senior author on the study, told The Guardian that the research provides "the strongest evidence yet" on how the harms of traffic pollution can be prevented through ambitious clean-air zones.

Dr. Ian Mudway of Imperial College London, another joint senior author, described the scale of the recovery as "remarkable" in comments reported by the BMJ on August 19, 2026, comparing it favorably to the limited lung recovery typically seen in adults who quit smoking. Mudway separately told Imperial College London, in a statement published the same day, that clean air zones are an effective public health intervention for preventing damage to developing lungs.

Why the comparison to smokers matters: children's lungs are still being built, and a stunted lung at age nine tends to stay stunted for life, which is why researchers have spent decades trying to establish whether pollution-linked damage can be undone rather than merely halted.

A longer story than one policy

The London findings echo research from another polluted city a generation earlier. Inside Climate News, in a report published August 26, 2026, compared the CHILL study to the Southern California Children's Health Study from 2001, which found that children who physically moved to areas with cleaner air saw their lung function improve. Ed Avol, a professor emeritus at the University of Southern California, called the new London results consistent with those earlier findings on restorative lung growth.

The California study showed that individual families could get cleaner air for their children through a move. The London study shows a government policy achieved something similar for an entire city's worth of children who never had to move at all.

Before the zone existed, London children were breathing nearly double the NO2 levels of their counterparts in Luton, according to a summary of the underlying Lancet Public Health research published by the European Lung Foundation on August 20, 2026. That summary notes researchers used spirometry tests at annual school visits over the full five-year study period to track how children's lungs developed year by year, rather than relying on a single before-and-after snapshot.

The Science Media Centre, gathering independent expert reaction on August 18, 2026, noted that the study's design cannot rule out other differences between London and Luton that changed over the same period, from housing to household income. Researchers involved in the project have said the size of the effect, and its consistency across separate measures of lung size and lung impairment, makes traffic pollution the most plausible explanation. The CHILL team's own published material does not identify a competing explanation that fits the data as well.

What the study does establish, on the numbers its authors have published, is that a city-wide policy change coincided with a measurable narrowing of a lung-health gap between two groups of children who started five years apart in very different places.

Sources

This article was reported from the following sources.

1. Impact of ULEZ on children's lung function growth, 2026 — Queen Mary University of London, 2026-08-18

2. Ulez led to better lung size and function among London children, study finds — The Guardian, 2026-08-18

3. Introducing London's ULEZ linked to improved child lung growth — NIHR (National Institute for Health and Care Research), 2026-08-19

4. Child lung health in London has improved since ULEZ was introduced, study claims — BMJ, 2026-08-19

5. Introduction of London's ULEZ linked to improved lung growth in children — Imperial College London, 2026-08-19

6. Study of 3400 children links London's Ultra Low Emission Zone with improved lung growth — University of Oxford, 2026-08-19

7. ULEZ and lung function in children in London — Science Media Centre, 2026-08-18

8. Cleaner Air Associated With Faster Lung Growth in London Children — AJMC (The American Journal of Managed Care), 2026-08-20

9. Clean air zones improve children's lung health: evidence from London's Ultra Low Emission Zone — European Lung Foundation, 2026-08-20

10. London's Ulez linked to healthier lung growth in children — Positive News, 2026-09-01

11. ULEZ Reverses Pollution-Linked Lung Deficits in London Children — EMJ (European Medical Journal), 2026-08-24

12. Clean Air Policies Help Kids Breathe and Think Better — Inside Climate News, 2026-08-26

13. In London, Children's Lungs Grow Faster as Traffic Pollution Falls — Good News Network, 2026-08-31

All source links verified at time of publication.