London’s ULEZ linked to improved lung growth in children

19 August 2026

The five-year Children’s Health in London and Luton (CHILL) study aimed to determine whether air quality improvements following the introduction of the ULEZ improved impaired lung growth of children living in London. Working with schools and parents prior to the ULEZ implementation, researchers recruited over 3,400 children aged 6-9 from 84 primary schools in London and Luton, with Luton acting as a control site (with a similar mix of traffic pollutants, but no clean air zone).

The children’s lung size and health were monitored at annual school visits from 2018-2022, to assess the impact of air quality changes on lung development. Initial lung capacity measurements taken before the ULEZ was introduced showed that children in London had significantly smaller lungs compared with those living in Luton.

Data collected over five years show that, after the implementation of the ULEZ, lung size and health accelerated in London children, and improved to be comparable with that of children in Luton. The improved lung growth trajectories were strongly related to air quality improvements following the implementation of the ULEZ. Over the course of the study, the proportion of children with clinically impaired lung function fell from 14% to 9% in London, compared with a fall from 9% to 7% in Luton.

Failure to reach fully developed lungs by early adulthood increases the risk of children experiencing respiratory diseases such as asthma and COPD, cardiovascular and metabolic disease, and premature death as adults. These findings, showing that deficits in children’s lung growth and health can be restored, have major implications for improving the long-term health of children.

The study results present the first evidence that clean air zones may benefit child development, and endorses their place as an important public health policy. Authors say that consideration should be given to implementing ambitious clean air zones more widely to protect and promote children’s lifelong health.

Dr Helen Wood, WIPH Research Fellow and lead author, said:

“We already knew that the ULEZ reduced air pollution, but now we know that children’s lung health has improved at the same time, which is a very important finding for children and parents living in London. However, we must not be complacent; air pollution in both London and Luton (as well as other cities across the UK) remains above WHO guideline levels, so there is still work to be done.”

Professor Lucy Chappell, Chief Scientific Adviser at the Department of Health and Social Care (DHSC) and Chief Executive Officer of the NIHR, said:

“This research, funded by NIHR, will provide crucial evidence on real-life interventions that deliver life-changing health benefits for children. I would like to thank the 3,400 children and their families who took part. Research can only take place with the input and support of participants, and this study is a great example of how the UK's vibrant research sector is working with communities to transform lives.”

Health Minister Karin Smyth said:

"This study is a powerful reminder of the impact that air quality has on children's lung health, and will help to improve our understanding of how reductions in air pollution can restore normal lung growth among children, reduce the risk of respiratory illnesses in adulthood, and support our goal to give every child the best start in life.”

The study, published in The Lancet Public Health, was led by researchers from Queen Mary University of London in collaboration with Imperial College London and the Universities of Bedfordshire, Oxford, Cambridge, Edinburgh and Southern California, and was funded by the National Institute for Health and Care Research (NIHR).

Wood HE, Hajmohammadi H, Dove RE, Scales J, Tsocheva I, Chavda J, Kalsi HS, Cross L, Colligan G, Sartori L, Mitchell JE, Moon J, Lie E, Petrovic K, Keating M, Le J, Day B, Keighley A, Crichlow C, Mallari J, Beddows A, Assareh N, Stewart G, Dajnak D, Beevers S, Toffolutti V, Fletcher M, Mihaylova B, Balkwill F, Grigg J, Raine R, Mon-Williams M, van Sluijs E, Kelly FJ, Newby C, Stuart B, Gauderman WJ, Sheikh A, Randhawa G, Mudway IS, Griffiths CJ. Impact of the Ultra Low Emission Zone on lung function growth in children in London, UK: a prospective parallel cohort study. Lancet Public Health. 2026 Aug 18:S2468-2667(26)00163-5. doi: 10.1016/S2468-2667(26)00163-5. Epub ahead of print. PMID: 42612665.