Investigating the impact of London's Ultra Low Emission Zone on children's health: Children's Health in London and Luton (CHILL): Protocol for a prospective parallel cohort study

Colligan, G.; Tsocheva, I.; Scales, J.; Chavda, J.; Dove, R.; Kalsi, H.; Wood, H.; Cross, L.; Newby, C.; Hall, A.; Keating, M.; Petrovic, K.; Day, B.; Chrichlow, C.; Keighley, A.; Thomson, A.; Tomini, F.; Balkwill, F.; Mihaylova, B.; Grigg, J.; van Sluijs, E.; Fletcher, M.; Mon-Williams, M.; Wright, J.; Beevers, S.; Randhawa, G.; Eldridge, S.; Sheikh, A.; Gauderman, J.; Kelly, F.; Mudway, I. S.; Griffiths, C. J.

Introduction: Air pollution harms health across the life course. Children are at particular risk of adverse effects during development, which may impact on health in later life. Interventions that improve air quality are therefore urgently needed not only to improve public health now, but to prevent longer-term increased vulnerability to chronic disease. Low Emission Zones are a public health policy intervention aimed at reducing traffic-derived contributions to urban air pollution, but evidence that they deliver clear health benefits is lacking. We established a natural experiment design study (CHILL: Children's Health in London and Luton) to evaluate the impacts of the introduction of London's Ultra Low Emission Zone (ULEZ) on childrens health. Methods and analysis: CHILL is a prospective two-arm parallel longitudinal cohort study of children aged 6-9 years, attending primary schools in Central London (the focus of the first phase of the ULEZ) and Luton (a comparator site). The primary goal of the study is to examine the impact of changes in annual air pollutant exposures as oxides of nitrogen, nitrogen dioxide, particulate matter less than 2.5microns and 10microns (NOx, NO2, PM2.5, PM10 respectively) across the two sites on lung growth, measured as forced expiratory volume in one second (FEV1) and forced vital capacity (FVC), over four consecutive years. Secondary outcomes being investigated include a range of respiratory health indicators as well as inequality and health economic measures. Ethics and dissemination: Ethics approval has been given by Queen Mary University of London Research Ethics Committee (ref 2018/08). Dissemination will target audiences through a variety of channels, including research papers, conference and media presentations, web summaries and social media. CHILL is funded by National Institute for Health Research (NIHR) Public Health Research (Ref 16/139/09) with additional funding by Natural Environment Research Council, NIHR CLAHRC North Thames, NIHR ARC North Thames, and the Mayor of London. ClinicalTrials.gov: NCT04695093