title: Ambient gas concentrations and personal particulate matter exposures: implications for studying the health effects of particles.
abstract: BACKGROUND
  Data from a previous study conducted in Baltimore, MD, showed that ambient fine particulate matter less than 2.5 mum in diameter (PM2.5) concentrations were strongly correlated with corresponding personal PM2.5 exposures, whereas ambient O3, NO2, and SO2 concentrations were weakly correlated with their personal exposures to these gases. In contrast, many of the ambient gas concentrations were reasonable surrogates of personal PM2.5 exposures.
  
  
  METHODS
  Personal multipollutant exposures and corresponding ambient air pollution concentrations were measured for 43 subjects living in Boston, MA. The cohort consisted of 20 healthy senior citizens and 23 schoolchildren. Simultaneous 24-hour integrated PM2.5, O3, NO2, and SO2 personal exposures and ambient concentrations were measured. All PM2.5 samples were also analyzed for SO4 (sulfate). We analyzed personal exposure and ambient concentration data using correlation and mixed model regression analyses to examine relationships among (1) ambient PM2.5 concentrations and corresponding ambient gas concentrations; (2) ambient PM2.5 and gas concentrations and their respective personal exposures; (3) ambient gas concentrations and corresponding personal PM2.5 exposures; and (4) personal PM2.5 exposures and corresponding personal gas exposures.
  
  
  RESULTS
  We found substantial correlations between ambient PM2.5 concentrations and corresponding personal exposures over the course of time. Additionally, our results support the earlier finding that summertime gaseous pollutant concentrations may be better surrogates of personal PM2.5 exposures (especially personal exposures to PM2.5 of ambient origin) than they are surrogates of personal exposures to the gases themselves.
  
  
  CONCLUSIONS
  Particle health effects studies that include both ambient PM2.5 and gaseous concentrations as independent variables must be analyzed carefully and interpreted cautiously, since both parameters may be serving as surrogates for PM2.5 exposures.
authors.affiliation: Department of Environmental and Occupational Health, Rollins School of Public Health of Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, USA. jsarnat@sph.emory.edu
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Sarnat
authors.forename: Kathleen W
authors.initials: KW
authors.lastname: Brown
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.forename: Brent A
authors.initials: BA
authors.lastname: Coull
authors.forename: Petros
authors.initials: P
authors.lastname: Koutrakis
mesh_terms: D000368:Aged; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis*; D015142:Baltimore; D001900:Boston; D002648:Child; D006801:Humans; D010316:Particle Size; D012044:Regression Analysis; D012621:Seasons
chemical_list: D000393:Air Pollutants