title: The temporal lag structure of short-term associations of fine particulate matter chemical constituents and cardiovascular and respiratory hospitalizations.
abstract: BACKGROUND
  In air pollution time-series studies, the temporal pattern of the association of fine particulate matter (PM2.5; particulate matter ≤ 2.5 µm in aerodynamic diameter) and health end points has been observed to vary by disease category. The lag pattern of PM2.5 chemical constituents has not been well investigated, largely because daily data have not been available.
  
  
  OBJECTIVE
  We explored the lag structure for hospital admissions using daily PM2.5 chemical constituent data for 5 years in the Denver Aerosol Sources and Health (DASH) study.
  
  
  METHODS
  We measured PM2.5 constituents, including elemental carbon, organic carbon, sulfate, and nitrate, at a central residential site from 2003 through 2007 and linked these daily pollution data to daily hospital admission counts in the five-county Denver metropolitan area. Total hospital admissions and subcategories of respiratory and cardiovascular admissions were examined. We assessed the lag structure of relative risks (RRs) of hospital admissions for PM2.5 and four constituents on the same day and from 1 to 14 previous days from a constrained distributed lag model; we adjusted for temperature, humidity, longer-term temporal trends, and day of week using a generalized additive model.
  
  
  RESULTS
  RRs were generally larger at shorter lags for total cardiovascular admissions but at longer lags for total respiratory admissions. The delayed lag pattern was particularly prominent for asthma. Elemental and organic carbon generally showed more immediate patterns, whereas sulfate and nitrate showed delayed patterns.
  
  
  CONCLUSIONS
  In general, PM2.5 chemical constituents were found to have more immediate estimated effects on cardiovascular diseases and more delayed estimated effects on respiratory diseases, depending somewhat on the constituent.
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington 98105, USA. puha0@uw.edu
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Peel
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hannigan
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Dutton
authors.forename: Lianne
authors.initials: L
authors.lastname: Sheppard
authors.forename: Maggie L
authors.initials: ML
authors.lastname: Clark
authors.forename: Sverre
authors.initials: S
authors.lastname: Vedal
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D002318:Cardiovascular Diseases / Q000139:chemically induced* / Q000503:physiopathology; D003120:Colorado; D006760:Hospitalization; D006801:Humans; D010316:Particle Size; D012140:Respiratory Tract Diseases / Q000139:chemically induced* / Q000503:physiopathology
chemical_list: D000393:Air Pollutants