Investigating the impact of London’s Ultra Emission Zone (ULEZ) on children’s physical activity and travel patterns: baseline data from the CHILL Study

Introduction: London’s Ultra Low Emission Zone (ULEZ) is a global exemplar of a city wide public health programme to improve respiratory health by reducing traffic related air pollution. The Children’s Health in London and Luton (CHILL) physical activity study aims to establish whether the ULEZ improves respiratory health by encouraging healthier travel choices. CHILL is a two arm prospective parallel cohort study of 3414 children in Central London (intervention) and Luton (control). We report physical activity and travel choices in the year prior to the implementation of the ULEZ in April 2019.

Methods: Objective measures of daily physical activity (MVPA) were recorded by accelerometery collected over seven days in a subgroup of 2427 children aged 6-9 across both sites. Analysis was performed via multilevel modelling, adjusting for sex, ethnicity, age, school and total wear time. Categorical data was assessed via Chi squared testing.

Results: Children in London were more likely to use active travel methods to school, (88% Vs 59%, p<0.001) than control. Participants traveling to school by private car (mean, 95%-CI) engage in less daily MVPA activity (56.5[54.7, 58.2] min) than those who use active travel (61.8[60.9,62.7]min) or public transport (61.2[59.1, 63.2]min, p<0.001).

Conclusions: The control group (Luton) is comparable the UK national average for active travel methods, while the London group are more likely to use active travel to school. We are following the cohort longitudinally to evaluate whether the ULEZ instigates a shift to more active travel.