title: Estimating error in using ambient PM2.5 concentrations as proxies for personal exposures: a review.
abstract: BACKGROUND
  Several methods have been used to account for measurement error inherent in using ambient concentration of particulate matter < 2.5 microm/m(3) (PM(2.5)) as a proxy for personal exposure. Such methods commonly rely on the estimated correlation between ambient and personal PM(2.5) concentrations (r). However, studies of r have not been systematically and quantitatively assessed for publication bias or heterogeneity.
  
  
  METHODS
  We searched 7 electronic reference databases for studies of the within-participant correlation between ambient and personal PM(2.5).
  
  
  RESULTS
  We identified 567 candidate studies, 18 (3%) of which met inclusion criteria and were abstracted. The studies were published between 1999 and 2008, representing 619 nonsmoking participants aged 6-93 years in 17 European and North American cities. Correlation coefficients (median 0.54; range 0.09-0.83) were based on a median of 8 ambient-personal PM(2.5) pairs per participant (range 5-20) collected over 27-547 days. Overall, there was little evidence for publication bias (funnel plot symmetry tests: Begg's log-rank test, P 0.9; Egger's regression asymmetry test, P 0.2). However, strong evidence for heterogeneity was noted (Cochran's Q test for heterogeneity, P = 0.001). European locales, eastern longitudes in North America, higher ambient PM(2.5) concentrations, higher relative humidity, and lower between-participant variation in r were associated with increased r.
  
  
  CONCLUSIONS
  Characteristics of participants, studies, and the environments in which they are conducted may affect the accuracy of ambient PM2.5 as a proxy for personal exposure.
authors.affiliation: Department of Epidemiology, University of North Carolina Chapel Hill, Bank of America Center, 137 E. Franklin St., Suite 306, Chapel Hill, NC 27514. christy_avery@unc.edu
authors.forename: Christy L
authors.initials: CL
authors.lastname: Avery
authors.forename: Katherine T
authors.initials: KT
authors.lastname: Mills
authors.forename: Ronald
authors.initials: R
authors.lastname: Williams
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: McGraw
authors.forename: Charles
authors.initials: C
authors.lastname: Poole
authors.forename: Richard L
authors.initials: RL
authors.lastname: Smith
authors.forename: Eric A
authors.initials: EA
authors.lastname: Whitsel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D002648:Child; D003627:Data Interpretation, Statistical; D004781:Environmental Exposure / Q000009:adverse effects / Q000032:analysis*; D005060:Europe; D006801:Humans; D008875:Middle Aged; D009656:North America; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis*; D017594:Publication Bias / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D052638:Particulate Matter