Comparison of short-term variations (15-minute averages) in outdoor and indoor PM2.5 concentrations

Gurumurthy Ramachandran, John L. Adgate, Nicholas Hill, Ken Sexton, Gregory C. Pratt, Donald Bock

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Measurements of 15-min average PM2.5 concentrations were made with a real-time light-scattering instrument at both outdoor (central monitoring sites in three communities) and indoor (residential) locations over two seasons in the Minneapolis-St. Paul metropolitan area. These data are used to examine within-day variability of PM2.5 concentrations indoors and outdoors, as well as matched indoor-to-outdoor (I/O) ratios. Concurrent gravimetric measurements of 24-hr average PM2.5 concentrations were also obtained as a way to compare real-time measures with this more traditional metric. Results indicate that (1) within-day variability for both indoor and outdoor 15-min average PM2.5 concentrations was substantial and comparable in magnitude to day-to-day variability for 24-hr average concentrations; (2) some residences exhibited substantial variability in indoor aerosol characteristics from one day to the next; (3) peak values for indoor short-term (15-min) average PM2.5 concentrations routinely exceeded 24-hr average outdoor values by factors of 3-4; and (4) relatively strong correlations existed between indoor and outdoor PM2.5 concentrations for both 24-hr and 15-min averages.

Original languageEnglish (US)
Pages (from-to)1157-1166
Number of pages10
JournalJournal of the Air and Waste Management Association
Issue number7
StatePublished - Jul 2000

Bibliographical note

Funding Information:
This research was supported by a grant from the Academic Health Center, University of Minnesota, for “Interdisciplinary Research on the Health Effects of Airborne Particulate Matter.” We also benefited from synergy with a related research project funded by EPA through grant number R825241-01-0 to the Minnesota Pollution Control Agency. We are grateful for the technical support of Dr. Avula Sreenath, currently at TSI, Inc., and Mr. Rick Strassman of the Minnesota Pollution Control Agency. We especially thank the study participants for their patience and members of the field team for their perseverance.

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