title: Urban ambient particle metrics and health: a time-series analysis.
abstract: BACKGROUND
  Epidemiologic evidence suggests that exposure to ambient particulate matter is associated with adverse health effects. Little is known, however, about which components of the particulate mixture (size, number, source, toxicity) are most relevant to health. We investigated associations of a range of particle metrics with daily deaths and hospital admissions in London.
  
  
  METHODS
  Daily concentrations of particle mass (PM10, PM2.5, and PM(10-2.5)), measured using gravimetric, tapered-element-oscillating, and filter-dynamic-measurement-system samplers, as well as particle number concentration and particle composition (carbon, sulfate, nitrate and chloride), were collected from a background monitoring station in central London between 2000 and 2005. All-cause and cause-specific deaths and emergency admissions to hospital in London for the same period were also collected. A Poisson regression time-series model was used in the analysis.
  
  
  RESULTS
  The results were not consistent across the various outcomes and lags. Particle number concentration was associated with daily mortality and admissions, particularly for cardiovascular diseases lagged 1-day; increases in particle number concentration (10,166 n/cm3) were associated with 2.2% (95% confidence interval = 0.6% to 3.8%) and 0.6% (-0.4% to 1.7%) increases in cardiovascular deaths and admissions, respectively. Secondary pollutants, especially nonprimary PM2.5, nitrate and sulfate, were more important for respiratory outcomes.
  
  
  CONCLUSIONS
  This study provides some evidence that specific components of the particle mixture for air pollutants may be relevant to specific diseases. Interpretation should be cautious, however, in particular because exposures were based upon data from a single centrally located monitoring site. There is a need for replication with more comprehensive exposure data, both in London and elsewhere.
authors.affiliation: Division of Community Health Sciences and MRC-HPA Centre for Environment and Health, St. George's, University of London, London, United Kingdom. atkinson@sgul.ac.uk
authors.forename: Richard W
authors.initials: RW
authors.lastname: Atkinson
authors.forename: Gary W
authors.initials: GW
authors.lastname: Fuller
authors.forename: H Ross
authors.initials: HR
authors.lastname: Anderson
authors.forename: Roy M
authors.initials: RM
authors.lastname: Harrison
authors.forename: Ben
authors.initials: B
authors.lastname: Armstrong
mesh_terms: D000397:Air Pollution / Q000009:adverse effects / Q000032:analysis / Q000706:statistics & numerical data; D002318:Cardiovascular Diseases / Q000139:chemically induced / Q000453:epidemiology / Q000401:mortality; D016001:Confidence Intervals; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008131:London / Q000453:epidemiology; D009026:Mortality; D052638:Particulate Matter / Q000009:adverse effects* / Q000032:analysis; D016012:Poisson Distribution; D012044:Regression Analysis; D013997:Time Factors; D014504:Urban Health / Q000706:statistics & numerical data*
chemical_list: D052638:Particulate Matter