Study finds improvements in children's lung health after ULEZ introduction
A study led by Queen Mary University of London (QMUL) has found that improvements in air quality following the 2019 introduction of London's Ultra Low Emission Zone (ULEZ) were associated with improved lung health in children. The research, published in The Lancet Public Health, tracked more than 3,400 children aged 6 to 9 from 84 schools in London and Luton between 2018 and 2022.
The ULEZ introduced a 24-hour, seven days a week charge of £12.50 ($17) for vehicles that do not meet emissions standards. Initially covering the inner city, it was expanded in August 2023 to outer boroughs.
Key findings
Initially, children in London had significantly smaller lung capacity than those in Luton, a control town with a similar mix of traffic pollutants but no clean air zone. After ULEZ came into force, the London children's lung function improved until they were comparable with those in Luton.
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. Within five years, London children's exposure to nitrogen dioxide fell twice as fast and twice as much as that of the Luton children.
Luton did not introduce a clean air zone, but its local council took other actions to improve air quality during the study period, including reducing speed limits and developing cycling and walking networks.
Reactions and context
Mayor Sadiq Khan, who introduced the ULEZ in 2019, called it "my hardest decision as mayor of London." Health minister Karin Smyth said the study was "a powerful reminder of the impact that air quality has on children's lung health."
Researchers said the findings were a vindication of the policy, which had been criticised as a burden on motorists. "We provide the strongest evidence yet on how these harms can be prevented," said Chris Griffiths, joint senior author, in comments reported by The Guardian.
The study is the first evidence that clean air zones may benefit child development, according to the researchers. Children whose lungs fail to develop fully by early adulthood face an increased risk of respiratory conditions such as asthma and COPD, cardiovascular and metabolic disease, and premature death, previous research has shown.
Expert skepticism
Some statisticians urged caution. Stephen Burgess, a professor of biostatistics at the University of Cambridge, told the Science Media Centre that the findings were "striking" but questioned whether the improvement could be attributed to ULEZ, suggesting alternative explanations such as the Covid pandemic. Kevin McConway, emeritus professor of applied statistics at the Open University, said the study does not prove a link and was limited to two geographical areas.
Despite these caveats, joint senior author Ian Mudway said that clean air zones can be an effective public health intervention to prevent damage to developing lungs.