title: Can air pollution negate the health benefits of cycling and walking?
abstract: Active travel (cycling, walking) is beneficial for the health due to increased physical activity (PA). However, active travel may increase the intake of air pollution, leading to negative health consequences. We examined the risk-benefit balance between active travel related PA and exposure to air pollution across a range of air pollution and PA scenarios. The health effects of active travel and air pollution were estimated through changes in all-cause mortality for different levels of active travel and air pollution. Air pollution exposure was estimated through changes in background concentrations of fine particulate matter (PM2.5), ranging from 5 to 200μg/m3. For active travel exposure, we estimated cycling and walking from 0 up to 16h per day, respectively. These refer to long-term average levels of active travel and PM2.5 exposure. For the global average urban background PM2.5 concentration (22μg/m3) benefits of PA by far outweigh risks from air pollution even under the most extreme levels of active travel. In areas with PM2.5 concentrations of 100μg/m3, harms would exceed benefits after 1h 30min of cycling per day or more than 10h of walking per day. If the counterfactual was driving, rather than staying at home, the benefits of PA would exceed harms from air pollution up to 3h 30min of cycling per day. The results were sensitive to dose-response function (DRF) assumptions for PM2.5 and PA. PA benefits of active travel outweighed the harm caused by air pollution in all but the most extreme air pollution concentrations.
authors.affiliation: UKCRC Centre for Diet and Activity Research, MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge, UK. Electronic address: mkt27@medschl.cam.ac.uk.
authors.forename: Marko
authors.initials: M
authors.lastname: Tainio
authors.affiliation: Centre for Environmental Policy, Imperial College London, London, UK.
authors.forename: Audrey J
authors.initials: AJ
authors.lastname: de Nazelle
authors.affiliation: Physical Activity and Health Unit, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Götschi
authors.affiliation: Physical Activity and Health Unit, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
authors.forename: Sonja
authors.initials: S
authors.lastname: Kahlmeier
authors.affiliation: Center for Research in Environmental Epidemiology (CREAL), Barcelona, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain; Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Rojas-Rueda
authors.affiliation: Center for Research in Environmental Epidemiology (CREAL), Barcelona, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain; Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Nieuwenhuijsen
authors.affiliation: Centre for Epidemiological Research in Nutrition and Health, School of Public Health, University of São Paulo, São Paulo, Brazil.
authors.forename: Thiago Hérick
authors.initials: TH
authors.lastname: de Sá
authors.affiliation: Physical Activity for Health Research Centre (PAHRC), University of Edinburgh, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Kelly
authors.affiliation: UKCRC Centre for Diet and Activity Research, MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge, UK.
authors.forename: James
authors.initials: J
authors.lastname: Woodcock
mesh_terms: D000397:Air Pollution / Q000009:adverse effects*; D001642:Bicycling / Q000706:statistics & numerical data*; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D015444:Exercise; D006801:Humans; D052638:Particulate Matter / Q000032:analysis; D018570:Risk Assessment; D016138:Walking / Q000502:physiology*
chemical_list: D052638:Particulate Matter
keywords: Air pollution; Bicycling; Health Impact Assessment; Mortality; Physical activity; Risk–Benefit Assessment; Walking