Air quality improvements following the introduction of London's Ultra Low Emission Zone (ULEZ) are strongly associated with improvements to children's lung health and function.
These are the findings of a five-year study involving thousands of children in England, which suggest that improvements in air quality helped restore lung growth previously stunted by exposure to air pollution.
Researchers found that within the five years of the introduction of ULEZ, children's exposure to nitrogen dioxide (NO2) fell rapidly, and the proportion of children with clinically impaired lung function also declined.
According to the team, the findings demonstrate the benefits of such clean air policies on children's respiratory health.
Dr Ian Mudway, Associate Professor in the School of Public Health at Imperial College London and joint senior author said: "Air pollution is a global issue. If we want to improve the lives of children living in high-traffic urban environments, we need bold and ambitious measures. Our data demonstrates that clean air zones can be an effective public health intervention to prevent damage to developing lungs."
The study, funded by the National Institute of Health cand Care Research (NIHR), is published in the journal The Lancet Public Health.
Children's Lung Health
The Children's Health in London and Luton (CHILL) study set out to determine if air quality improvements following the introduction of the ULEZ could improve impaired lung growth of children living in London.
Researchers from Queen Mary University of London, Imperial College London and the Universities of Bedfordshire, Oxford, Cambridge, Edinburgh and Southern California (USA), recruited over 3,400 children aged 6-9 from 84 primary schools in London and Luton – with Luton acting as a comparison (control) site with a similar mix of traffic pollutants but no clean air zone.
Lung size and health were measured and monitored at annual visits from 2018 to 2022 to assess the impact of air quality changes. Initial lung capacity measurements taken before the ULEZ was introduced showed that children in London had significantly smaller lungs compared to children living in Luton, a finding consistent with the team's previous work.
Analysis showed that over the study period, London children's lungs size and health accelerated 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.
The team evaluated children's lung health and development by accurately assessing FEV1 – a measure of how much air can be forcefully exhaled from the lungs in one second following maximal inhalation – in relation to exposure to nitrogen dioxide (NO2), the pollutant most reflective of exhaust pollution.
Within the five-year period, London children's exposure to NO2 fell twice as fast and more than twice as much compared to children in Luton. At the end of the five years, FEV1 was the same across both groups. Also, over the course of the study, the team noted that 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.
Stunted lung growth in children increases the risk respiratory diseases such as asthma and COPD, cardiovascular and metabolic disease, and premature death in adulthood. The researchers say their findings, which show that deficits in children's lung growth and health can be restored, therefore have major implications for improving the long-term health of children.
Professor Chris Griffiths, Professor of Primary Care at the University of Oxford and at Queen Mary University of London, and joint senior author, said: "Traffic pollution in cities damages children's health and development. We provide the strongest evidence yet on how these harms can be prevented. Ambitious clean air zones should be considered a priority for cities globally with traffic-related air pollution."
Dr Helen Wood, Research Fellow at Queen Mary 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 really 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 Gurch Randhawa, Professor of Public Health at the University of Bedfordshire, and joint senior author said: "The findings provide evidence of the health benefits for children living in a clean air zone. This will be of interest to Luton and Bedfordshire as they plan for future development and regeneration."
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."
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'Impact of the Ultra Low Emission Zone on lung function growth in children in London, UK: a prospective parallel cohort study' by Helen Wood, Hajar Hajmohammadi, Rosamund Dove, et al. is published in The Lancet Public Health.
This article is based on materials from Queen Mary University of London.
