Reducing traffic pollution improves children’s lung capacity, study shows
The introduction of London’s Ultra Low Emission Zone (ULEZ) has been linked to improved lung growth in children, according to a study published today in The Lancet.
The study, involving thousands of children, found that air quality improvements following the introduction of London’s ULEZ are strongly associated with accelerated lung growth in children, restoring lung growth previously stunted by exposure to air pollution. The research was led by Queen Mary University of London in collaboration with Imperial College London and the Universities of Bedfordshire, Oxford, Cambridge, Edinburgh and Southern California and funded by the National Institute for Health and Care Research (NIHR).
Working closely with schools and parents prior to the implementation of the ULEZ, 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 measured and monitored at annual school visits from 2018 to 2022 to assess the impact of air quality changes on their lung development, following the introduction of the ULEZ in London. 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.
Reviewing data collected over the five years, the team found that after the implementation of the ULEZ, London children’s lungs size and health accelerated and improved to be comparable with that of children in Luton. Most importantly, they demonstrated that these improved lung growth trajectories were strongly related to air quality improvements following the implementation of the ULEZ.
The researchers evaluated children’s lung health and development by accurately assessing their forced expiratory volume in one second (FEV1), a measurement 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.
The researchers found that within the five years after ULEZ’s introduction, London children’s exposure to NO2 fell twice as fast and more than twice as much compared to children in Luton. They then demonstrated that as NO2 exposure decreased, London children’s FEV1 increased by 10ml per year more than children in Luton. At the end of the five years, the FEV1 was the same across children in London and Luton, indicating that the London children’s lung growth had accelerated during the five years to ‘catch up’ with the control group in Luton.
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.
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. The study’s authors conclude that 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.
A growing number of clean air zones are being implemented across the world. The London ULEZ was politically controversial, with London’s mayor Sadiq Khan coming under sustained attack from political opponents on the right. This important evidence that ULEZ benefits child development and public health strengthens the case for the policy and also highlights the urgent need for generous financial support packages to enable car dependent lower income motorists to switch from older, gross polluting vehicles.
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.”
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.”
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