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 PM10–2.5), 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.
From the aDivision of Community Health Sciences and MRC-HPA Centre for Environment and Health, St. George's, University of London, London, United Kingdom; bEnvironmental Research Group, MRC-HPA Centre for Environment and Health, King's College London, London, United Kingdom; cDivision of Environmental Health and Risk Management, University of Birmingham, Birmingham, United Kingdom; and dPublic and Environmental Health Research Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Submitted 26 February 2009; accepted 6 November 2009.
Supported by the Department for Environment, Food and Rural Affairs (DEFRA) in partnership with the Scottish Executive, Welsh Assembly Government and the DoE in Northern Ireland (Contract number AQ05515/CPEA 30).
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Correspondence: Richard W. Atkinson, Division of Community Health Sciences and MRC-HPA Centre for Environment and Health, 6th Floor, Hunter Wing, St. George's, University of London, Cranmer Terrace, London SW17 0RE. E-mail: firstname.lastname@example.org.