NEW research has found that children in London experienced faster lung function growth than children in Luton following introduction of the Ultra Low Emission Zone (ULEZ), with lung development differences between the two groups no longer apparent after four years.
The prospective parallel cohort study followed children aged six to nine years in central London and Luton, a comparator area without a clean air zone. Researchers recruited 3,414 children before ULEZ implementation and measured lung function annually over five years.
A total of 3,209 children were included in the primary forced expiratory volume in 1 s (FEV1) analysis. At baseline, adjusted FEV1 was 38 mL lower among children in London than those in Luton (95% CI: –58 to –18; p=0.0002).
However, lung function growth subsequently increased by 10 mL/year more in London than in Luton (95% CI: 5–15; p=0.0002), reaching 233 mL/year compared with 223 mL/year, respectively.
At baseline, annual modelled residential exposure to nitrogen dioxide (NO2), described by the researchers as the pollutant most reflective of exhaust emissions, was 18.95 μg/m3 higher in London than in Luton (95% CI: 18.51–19.38; p<0.0001).
During follow-up, estimated NO2 exposure decreased more rapidly in London, falling by 3.77 μg/m3 per year compared with 1.77 μg/m3 per year in Luton (p<0.0001).
After four years, mean FEV1 was similar between the groups, at 2283 mL in London and 2282 mL in Luton. The proportion of children with clinically impaired lung function also decreased over follow-up in both locations, from 14% to 9% in London and from 9% to 7% in Luton.
The researchers interpreted the findings as evidence that ULEZ introduction was associated with improved lung function growth trajectories among children in London compared with those in Luton, suggesting that earlier differences in lung development were restored.
The authors said the results support wider implementation of clean air zones as a public health intervention. However, the study was designed as a natural experiment comparing two locations rather than a randomised trial, and the findings therefore describe an association between the policy change, pollution exposure and lung function growth.
Reference
Wood H et al. Impact of the Ultra Low Emission Zone on lung function growth in children in London, UK: a prospective parallel cohort study. Lancet Public Health. 2026;11:e733-43.
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