title: Long-term exposure to ambient ozone and mortality: a quantitative systematic review and meta-analysis of evidence from cohort studies.
abstract: OBJECTIVE
  While there is good evidence for associations between short-term exposure to ozone and a range of adverse health outcomes, the evidence from narrative reviews for long-term exposure is suggestive of associations with respiratory mortality only. We conducted a systematic, quantitative evaluation of the evidence from cohort studies, reporting associations between long-term exposure to ozone and mortality.
  
  
  METHODS
  Cohort studies published in peer-reviewed journals indexed in EMBASE and MEDLINE to September 2015 and PubMed to October 2015 and cited in reviews/key publications were identified via search strings using terms relating to study design, pollutant and health outcome. Study details and estimate information were extracted and used to calculate standardised effect estimates expressed as HRs per 10 ppb increment in long-term ozone concentrations.
  
  
  RESULTS
  14 publications from 8 cohorts presented results for ozone and all-cause and cause-specific mortality. We found no evidence of associations between long-term annual O3 concentrations and the risk of death from all causes, cardiovascular or respiratory diseases, or lung cancer. 4 cohorts assessed ozone concentrations measured during the warm season. Summary HRs for cardiovascular and respiratory causes of death derived from 3 cohorts were 1.01 (95% CI 1.00 to 1.02) and 1.03 (95% CI 1.01 to 1.05) per 10 ppb, respectively.
  
  
  CONCLUSIONS
  Our quantitative review revealed a paucity of independent studies regarding the associations between long-term exposure to ozone and mortality. The potential impact of climate change and increasing anthropogenic emissions of ozone precursors on ozone levels worldwide suggests further studies of the long-term effects of exposure to high ozone levels are warranted.
authors.affiliation: Population Health Research Institute and MRC-PHE Centre for Environment and Health, St George's, University of London, London, UK.
authors.forename: R W
authors.initials: RW
authors.lastname: Atkinson
authors.affiliation: Population Health Research Institute and MRC-PHE Centre for Environment and Health, St George's, University of London, London, UK.
authors.forename: B K
authors.initials: BK
authors.lastname: Butland
authors.affiliation: Environmental Change Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Oxon, UK.
authors.forename: C
authors.initials: C
authors.lastname: Dimitroulopoulou
authors.affiliation: School of Chemistry, University of Edinburgh, Edinburgh, UK.
authors.forename: M R
authors.initials: MR
authors.lastname: Heal
authors.affiliation: RICARDO-AEA, Harwell IBC, Didcot, Oxfordshire, UK.
authors.forename: J R
authors.initials: JR
authors.lastname: Stedman
authors.affiliation: Environment Department, University of York, York, UK.
authors.forename: N
authors.initials: N
authors.lastname: Carslaw
authors.affiliation: National Heart & Lung Institute, Imperial College London and MRC-PHE Centre for Environment & Health, Imperial College London, London, UK.
authors.forename: D
authors.initials: D
authors.lastname: Jarvis
authors.affiliation: Environmental Change Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Oxon, UK.
authors.forename: C
authors.initials: C
authors.lastname: Heaviside
authors.affiliation: Environmental Change Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Oxon, UK.
authors.forename: S
authors.initials: S
authors.lastname: Vardoulakis
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: H
authors.identifier: http://orcid.org/0000-0002-9252-3962
authors.initials: H
authors.lastname: Walton
authors.affiliation: Population Health Research Institute and MRC-PHE Centre for Environment and Health, St George's, University of London, London, UK MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: H R
authors.initials: HR
authors.lastname: Anderson
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects*; D000397:Air Pollution / Q000009:adverse effects*; D002318:Cardiovascular Diseases / Q000401:mortality; D002423:Cause of Death; D015331:Cohort Studies; D006801:Humans; D009026:Mortality; D010126:Ozone / Q000009:adverse effects*; D012140:Respiratory Tract Diseases / Q000401:mortality; D012307:Risk Factors; D012621:Seasons; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D010126:Ozone
keywords: Air Pollution; EPIDEMIOLOGY; Mortality; Ozone; PUBLIC HEALTH; Systematic review