Children had lung function tests every year
Scientists say they have been "stunned" by how quickly young children's lungs began to recover and grow after pollution restrictions were brought in where they lived.
Researchers found that children in London whose lung growth had been stunted by pollution showed impressive improvements after the introduction of an Ultra Low Emission Zone (Ulez) in 2019 reduced emissions.
The study followed more than 3,400 primary school children in London and Luton and provides what scientists believe is the strongest evidence yet that local clean air zones could help reduce some of the harm caused by pollution during childhood.
But independent researchers caution that other factors must also be considered.
Air pollution can stunt the growth of young children's lungs leaving them at an increased risk of asthma, heart disease, diabetes and even premature death.
Children are also more vulnerable to pollution because their lungs and immune systems are still developing. And when outside, they tend to be closer to the ground and nearer sources of exhaust fumes, for example.
In 2020 Ella Adoo-Kissi-Debrah, a nine-year-old girl from London who died following an asthma attack in 2013, became the first person in the UK to have air pollution listed as a cause of death.
In the study, researchers recruited six to nine-year-olds attending primary schools in London's ultra low emission zone and followed the same children for five years, comparing them to similar children (in terms of socio-economic background, physical activity and ethnicity) in Luton.
Children in the study had annual lung function and capacity tests in the year before Ulez came in and for four years after.
Initial results showed children's lungs in London were smaller in capacity than those in Luton, which is less polluted than London but has a similar mix of pollutants.
At the end of the study the children's lung capacity reached near identical levels in both groups.
"While we would expect children's lungs to grow year on year, our results indicate that the London children's lung growth had accelerated during the four years to 'catch up' with the control group in Luton to reach similar levels of lung capacity," researchers say.
"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC.
"The speed of catch up in lung capacity in the London group was surprising and impressive.
