BY THE OPTIMIST DAILY EDITORIAL TEAM
For years, researchers knew that air pollution stunts lung development in children. What they hadn’t been able to show was whether cleaning up the air could actually change that trajectory.
A study published in The Lancet Public Health suggests it can. Scientists at Queen Mary University of London followed more than 3,400 children aged 6 to 9 over several years, tracking their lung development as London’s Ultra Low Emission Zone took effect. The ULEZ restricts or charges drivers of more polluting vehicles to encourage cleaner transport, and it handed researchers something they rarely get: a natural experiment.
By comparing children in central London to a similar group in Luton, where no clean-air zone existed, they could isolate what the policy actually did.
What the data demonstrates
Nitrogen dioxide levels, closely linked to vehicle exhaust, fell roughly twice as fast in central London as in Luton: about 3.8 micrograms per cubic metre per year in London, compared with 1.8 in Luton. Both cities improved, but not at the same pace.
Lung function moved with it. Researchers measured how much air each child could forcefully exhale in one second, a standard test of lung capacity. Before the ULEZ, London children had slower lung growth than those in Luton. As pollution fell, that changed. London children’s lung function grew by an average of 233 millilitres per year, versus 223 in Luton. After four years, the gap was gone. The London children had caught up entirely.
The share of central London children with impaired lung function fell from 14 percent to nine percent over that same stretch.
Why childhood lungs are different
Lungs aren’t fully developed at birth. They keep growing through childhood and into early adulthood, and what happens during those years shapes a person’s respiratory health for the rest of their life. Children whose lungs don’t develop fully face higher lifetime risks of asthma and other conditions. This is the first study to connect a clean-air zone directly to faster lung growth: a change measurable in children’s bodies, not just in air quality readings.
The political context
The ULEZ hasn’t been without pushback. Its cameras have been vandalized or stolen, according to the Metropolitan Police, and the 2023 expansion across all London boroughs was challenged in court by several local councils before the High Court let it proceed. The science is now adding some weight to one side of that fight.
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