Investigating the impact of London’s Ultra Low Emission Zone (ULEZ) on children’s respiratory health: lung function of participants in the CHILL Study

Children are vulnerable to the effects of traffic-related air pollution (TRAP). Early exposure impairs lung growth and development and increases the risk of chronic illness. Low Emission Zones aim to reduce TRAP in urban areas. However, the evidence that such initiatives improve health requires further investigation. London’s Ultra Low Emission Zone was implemented in April 2019, delivering rapid improvements in air quality. The Children’s Health in London and Luton (CHILL) study investigates its impact on the respiratory health of children.

CHILL is a 5-year prospective two-arm parallel longitudinal cohort study of multi-ethnic children (6-9 years) attending 85 schools in central London (ULEZ site) and Luton (comparator site). We report post-bronchodilator spirometry at baseline prior to ULEZ implementation.

Of 3414 children recruited, 2577 (75.5%) successfully completed post-bronchodilator spirometry, 1255 in London and 1322 in Luton. Results (Mean ± SD) for London and Luton respectively were FEV1 (1.57 ± 0.30 vs. 1.57 ± 0.29 L), FVC (1.79 ± 0.35 vs. 1.81 ± 0.34 L), FEV1/FVC (87.8 ± 0.06 vs. 87.2 ± 0.06 %, p = 0.0135), and MMEF75/25 (2.10 ± 0.55 vs. 2.08 ± 0.53 L/s). Mean GLI z-scores in London and Luton for FEV1 (0.14 ± 1.08 vs. 0.18 ± 1.12), FVC (0.49 ± 1.07 vs. 0.72 ± 1.06), FEV1/FVC (-0.30 ± 1.04 vs. -0.47 ± 0.99, p <0.0001), and MMEF75/25 (0.30 ± 1.01 vs. 0.32 ± 1.07).

Lung function of children prior to ULEZ implementation was well-matched across the intervention ULEZ site (London) and the comparator site (Luton), providing a sound basis for analyses of the impacts of ULEZ implementation on lung function growth trajectories.