title: Short-term associations between particle oxidative potential and daily mortality and hospital admissions in London.
abstract: Particulate matter (PM) from traffic and other sources has been associated with adverse health effects. One unifying theory is that PM, whatever its source, acts on the human body via its capacity to cause damaging oxidation reactions related to its content of pro-oxidants components. Few epidemiological studies have investigated particle oxidative potential (OP) and health. We conducted a time series analysis to assess associations between daily particle OP measures and numbers of deaths and hospital admissions for cardiovascular and respiratory diseases.
  
  
  
  During 2011 and 2012 particles with an aerodynamic diameter less than 2.5 and 10μm (PM2.5 and PM10 respectively) were collected daily on Partisol filters located at an urban background monitoring station in Central London. Particulate OP was assessed based on the capacity of the particles to oxidize ascorbate (OP(AA)) and glutathione (OP(GSH)) from a simple chemical model reflecting the antioxidant composition of human respiratory tract lining fluid. Particulate OP, expressed as % loss of antioxidant per μg of PM, was then multiplied by the daily concentrations of PM to derive the daily OP of PM mass concentrations (% loss per m(3)). Daily numbers of deaths and age- and cause-specific hospital admissions in London were obtained from national registries. Poisson regression accounting for seasonality and meteorology was used to estimate the percentage change in risk of death or admission associated with an interquartile increment in particle OP.
  
  
  
  We found little evidence for adverse associations between OP(AA) and OP(GSH) and mortality. Associations with cardiovascular admissions were generally positive in younger adults and negative in older adults with confidence intervals including 0%. For respiratory admissions there was a trend, from positive to negative associations, with increasing age although confidence intervals generally included 0%.
  
  
  
  Our study, the first to analyse daily particle OP measures and mortality and admissions in a large population over two years, found little evidence to support the hypothesis that short-term exposure to particle OP is associated with adverse health effects. Further studies with improved exposure assessment and longer time series are required to confirm or reject the role of particle OP in triggering exacerbations of disease.
authors.affiliation: Population Health Research Institute and MRC-PHE Centre for Environment and Health, St George's, University of London, Cranmer Terrace, London SW17 0RE, UK. Electronic address: atkinson@sgul.ac.uk.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Atkinson
authors.affiliation: Department of Hygiene, Epidemiology and Medical Statistics, Medical school, University of Athens, 75 Mikras Asias Str, 115 27 Athens, Greece.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Samoli
authors.affiliation: Department of Hygiene, Epidemiology and Medical Statistics, Medical school, University of Athens, 75 Mikras Asias Str, 115 27 Athens, Greece.
authors.forename: Antonis
authors.initials: A
authors.lastname: Analitis
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Fuller
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: David C
authors.initials: DC
authors.lastname: Green
authors.affiliation: Population Health Research Institute and MRC-PHE Centre for Environment and Health, St George's, University of London, Cranmer Terrace, London SW17 0RE, UK; MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: H Ross
authors.initials: HR
authors.lastname: Anderson
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: Esme
authors.initials: E
authors.lastname: Purdie
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: Chrissi
authors.initials: C
authors.lastname: Dunster
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: Layla
authors.initials: L
authors.lastname: Aitlhadj
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Kelly
authors.affiliation: MRC-PHE Centre for Environment and Health, King's College London, London, UK.
authors.forename: Ian S
authors.initials: IS
authors.lastname: Mudway
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D000975:Antioxidants / Q000737:chemistry; D001205:Ascorbic Acid / Q000737:chemistry; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D004784:Environmental Monitoring; D005978:Glutathione / Q000737:chemistry; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008131:London / Q000453:epidemiology; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000032:analysis / Q000737:chemistry; D010084:Oxidation-Reduction; D010126:Ozone / Q000032:analysis / Q000737:chemistry; D052638:Particulate Matter / Q000032:analysis* / Q000737:chemistry; D012140:Respiratory Tract Diseases / Q000453:epidemiology*; D013458:Sulfur Dioxide / Q000032:analysis / Q000737:chemistry; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D000975:Antioxidants; D052638:Particulate Matter; D013458:Sulfur Dioxide; D010126:Ozone; D005978:Glutathione; D001205:Ascorbic Acid; D009585:Nitrogen Dioxide
keywords: Environmental epidemiology; Hospital admissions; Mortality; Oxidative potential; Particles; Time series