title: Exposure to ambient and nonambient components of particulate matter: a comparison of health effects.
abstract: BACKGROUND
  Numerous epidemiologic studies report associations between outdoor concentrations of particles and adverse health effects. Because personal exposure to particles is frequently dominated by exposure to nonambient particles (those originating from indoor sources), we present an approach to evaluate the relative impacts of ambient and nonambient exposures.
  
  
  METHODS
  We developed separate estimates of exposures to ambient and nonambient particles of different size ranges (PM2.5, PM10-2.5 and PM10) based on time-activity data and the use of particle sulfate measurements as a tracer for indoor infiltration of ambient particles. To illustrate the application of these estimates, associations between cardiopulmonary health outcomes and the estimated exposures were compared with associations computed using measurements of personal exposures and outdoor concentrations for a repeated-measures panel study of 16 patients with chronic obstructive pulmonary disease conducted in the summer of 1998 in Vancouver.
  
  
  RESULTS
  Total personal fine particle exposures were dominated by exposures to nonambient particles, which were not correlated with ambient fine particle exposures or ambient concentrations. Although total and nonambient particle exposures were not associated with any of the health outcomes, ambient exposures (and to a lesser extent ambient concentrations) were associated with decreased lung function, decreased systolic blood pressure, increased heart rate, and increased supraventricular ectopic heartbeats. Measures of heart rate variability showed less consistent relationships among the various exposure metrics.
  
  
  CONCLUSIONS
  These results demonstrate the usefulness of separating total personal particle exposures into their ambient and nonambient components. The results support previous epidemiologic findings using ambient concentrations by demonstrating an association between health outcomes and ambient (outdoor origin) particle exposures but not with nonambient (indoor origin) particle exposures.
authors.affiliation: Department of Environmental and Occupational Health, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, USA.
authors.forename: Stefanie T
authors.initials: ST
authors.lastname: Ebelt
authors.forename: William E
authors.initials: WE
authors.lastname: Wilson
authors.forename: Michael
authors.initials: M
authors.lastname: Brauer
mesh_terms: D000368:Aged; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis*; D001794:Blood Pressure / Q000187:drug effects; D001955:British Columbia; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008875:Middle Aged; D010316:Particle Size; D029424:Pulmonary Disease, Chronic Obstructive; D012119:Respiration / Q000187:drug effects
chemical_list: D000393:Air Pollutants