Abstract
Much of human exposure to particulate matter (PM) of ambient origin occurs indoors. While the oxidative potential (OP) of PM is an emerging indicator of the intrinsic toxicity of PM, little is known about the OP of indoor PM of ambient origin. Here we characterize the OP of indoor and outdoor size-resolved PM in an unoccupied apartment unit in Chicago, IL, free from indoor emission sources, to explore how the transport of ambient PM from outdoors affects OP indoors. Simultaneous measurements were conducted in both indoor and outdoor locations for at least 5 consecutive days during 11 separate sampling campaigns spanning all seasons. OP was assessed by the dithiothreitol (DTT) assay. Indoor PM2.5 concentrations were consistently lower than outdoor PM2.5 concentrations, with an average (±standard deviation, SD) indoor/outdoor (I/O) PM2.5 mass concentration ratio of 0.36 ± 0.10. The volume-normalized (or extrinsic) OP of the particles was much higher for the outdoor for PM2.5 samples across all size-ranges, with an average (±SD) indoor-to-outdoor ratio (I/O) of 0.54 ± 0.57. However, the mass-normalized (or intrinsic) OP of indoor PM2.5 samples was greater than concurrent outdoor PM2.5 samples during 7 of the sampling periods and had an overall average ± SD I/O of 1.38 ± 0.97. The extent of enhancement in intrinsic OP of ambient-infiltrated indoor PM2.5 was positively correlated with differences in indoor and outdoor temperature and relative humidity (RH). We hypothesize that changes in the intrinsic OP of ambient PM as it infiltrates indoors may be influenced by transformation processes such as size-resolved penetration, indoor deposition, evaporation of volatile chemical components with lower OP, and/or temperature/RH-dependent partitioning of redox-active substances to indoor-infiltrated PM. However, further investigations, including chemical analyses of the size-segregated indoor and outdoor PM samples and the effect of environmental factors on this chemical composition, will be needed to confirm these hypotheses.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
