Children’s Health in London and Luton (CHILL) cohort: a 12-month natural experimental study of the effects of the Ultra Low Emission Zone on children’s travel to school oleh Christina Xiao, James Scales, Jasmine Chavda, Rosamund E. Dove, Ivelina Tsocheva, Helen E. Wood, Harpal Kalsi, Luke Sartori, Grainne Colligan, Jessica Moon, Esther Lie, Kristian Petrovic, Bill Day, Cheryll Howett, Amanda Keighley, Borislava Mihaylova, Veronica Toffolutti, Jonathan Grigg, Gurch Randhawa, Aziz Sheikh, Monica Fletcher, Ian Mudway, Sean Beevers, W. James Gauderman, Christopher J. Griffiths, Esther van Sluijs, Jenna Panter