Estimating error in using residential outdoor PM2.5 concentrations as proxies for personal exposures: a meta-analysis.
BACKGROUND
Studies examining the health effects of particulate matter <or= 2.5 microm in aerodynamic diameter (PM2.5) commonly use ambient PM2.5 concentrations measured at distal monitoring sites as proxies for personal exposure and assume spatial homogeneity of ambient PM2.5. An alternative proxy-the residential outdoor PM2.5 concentration measured adjacent to participant homes-has few advantages under this assumption.


OBJECTIVE
We systematically reviewed the correlation between residential outdoor PM2.5 and personal PM2.5 (-rj) as a means of comparing the magnitude and sources of measurement error associated with their use as exposure surrogates.


METHODS
We searched seven electronic reference databases for studies of the within-participant residential outdoor-personal PM2.5 correlation.


RESULTS
The search identified 567 candidate studies, nine of which were abstracted in duplicate, that were published between 1996 and 2008. They represented 329 nonsmoking participants 6-93 years of age in eight U.S. cities, among whom -rj was estimated (median, 0.53; range, 0.25-0.79) based on a median of seven residential outdoor-personal PM2.5 pairs per participant. We found modest evidence of publication bias (symmetric funnel plot; pBegg = 0.4; pEgger = 0.2); however, we identified evidence of heterogeneity (Cochran's Q-test p = 0.05). Of the 20 characteristics examined, earlier study midpoints, eastern longitudes, older mean age, higher outdoor temperatures, and lower personal-residential outdoor PM2.5 differences were associated with increased within-participant residential outdoor-personal PM2.5 correlations.


CONCLUSIONS
These findings were similar to those from a contemporaneous meta-analysis that examined ambient-personal PM2.5 correlations (rj = median, 0.54; range, 0.09-0.83). Collectively, the meta-analyses suggest that residential outdoor-personal and ambient-personal PM2.5 correlations merit greater consideration when evaluating the potential for bias in studies of PM2.5-mediated health effects.
Avery
Christy L
CL
Department of Epidemiology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27514 , USA. christy_avery@unc.edu
Mills
Katherine T
KT
Williams
Ronald
R
McGraw
Kathleen A
KA
Poole
Charles
C
Smith
Richard L
RL
Whitsel
Eric A
EA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D004782:Environmental Health; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000008:administration & dosage* / Q000633:toxicity*; D014481:United States; D055815:Young Adult
D052638:Particulate Matter