How does infiltration behavior modify the composition of ambient PM2.5 in indoor spaces? An analysis of RIOPA data.
The indoor environment is an important venue for exposure to fine particulate matter (PM2.5) of ambient (outdoor) origin. In this work, paired indoor and outdoor PM2.5 species concentrations from three geographically distinct cities (Houston, TX, Los Angeles County, CA, and Elizabeth, NJ) were analyzed using positive matrix factorization (PMF) and demonstrate that the composition and source contributions of ambient PM2.5 are substantially modified by outdoor-to-indoor transport. Our results suggest that predictions of "indoor PM2.5 of ambient origin" are improved when ambient PM2.5 is treated as a combination of four distinct particle types with differing infiltration behavior (primary combustion, secondary sulfate and organics, secondary nitrate, and mechanically generated PM) rather than as a "single internally mixed entity". Study-wide average infiltration factors (i.e., fraction of ambient PM2.5 found indoors) for Relationship of Indoor, Outdoor, and Personal Air (RIOPA) study homes were 0.51, 0.78, and 0.04 (consistent with P = 0.6, 0.9, and 0.09; k = 0.2, 0.1, and 0.6 h(-1)) for PM2.5 associated with primary combustion, secondary formation (excluding nitrate), and mechanical generation, respectively. Modification of the composition, properties, and source contributions of ambient PM2.5 in indoor environments has important implications for exposure mitigation strategies, development of health hypotheses, and evaluation of exposure error in epidemiological studies that use ambient central-site PM2.5 as a surrogate for PM2.5 exposure.
Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901, USA.
Qing Yu
QY
Meng
Barbara J
BJ
Turpin
Jong Hoon
JH
Lee
Andrea
A
Polidori
Clifford P
CP
Weisel
Maria
M
Morandi
Steven
S
Colome
Junfeng
J
Zhang
Thomas
T
Stock
Arthur
A
Winer
D000393:Air Pollutants / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis*; D002244:Carbon / Q000032:analysis; D004784:Environmental Monitoring; D006798:Housing; D015141:Los Angeles; D008670:Metals / Q000032:analysis; D009515:New Jersey; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012623:Seawater; D012825:Silicon / Q000032:analysis; D012987:Soil; D013781:Texas
D000393:Air Pollutants; D008670:Metals; D052638:Particulate Matter; D012987:Soil; D002244:Carbon; D012825:Silicon