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Spatiotemporal Variability in the Oxidative Potential of Ambient Fine Particulate Matter in Midwestern United States
HAORAN YU, Joseph V Puthussery, Yixiang Wang, Vishal Verma, University of Illinois Urbana-Champaign
Abstract Number: 148
Working Group: Health-Related Aerosols
Abstract
Oxidative potential (OP) of fine particulate matter (PM2.5) has been proposed as an important mechanism for many PM2.5-related health outcomes. The spatiotemporal profile of PM2.5 OP could be extremely helpful in assessing the regional health effects of PM2.5, and such profiles have been developed from many geographical regions of the world. However, no prior studies have investigated the spatiotemporal distribution of PM2.5 OP in the Midwestern United States (Midwest US). Here, we conducted the first study on assessing the OP of both water-soluble and methanol-soluble fractions of ambient PM2.5 in the Midwest US. PM2.5 samples (N = 241) were sampled from five sites located in urban, rural, and roadside environments of Illinois, Indiana, and Missouri within a year. We used five acellular endpoints, including the consumption rate of ascorbic acid and glutathione in a surrogate lung fluid (SLF) (OPAA and OPGSH, respectively), dithiothreitol (DTT) depletion rate (OPDTT), and ∙OH generation rate in SLF and DTT (OPOH-SLF and OPOH-DTT, respectively), for analyzing the OP of all PM2.5 samples. Compared to the homogeneously distributed PM2.5 mass concentrations, all OP endpoints showed substantial variability both spatially and temporally. In general, both water-soluble and methanol-soluble OP showed elevated levels during summer. The roadside site had the highest activities for most OP endpoints. The distribution trends between mass- and volume-normalized OP were similar for most endpoints indicating only a minor role of mass in controlling the OP. Higher levels were observed in methanol-soluble OP than water-soluble OP, indicating a better efficiency of methanol to extract the redox-active components in PM2.5. Correlations between PM2.5 mass concentrations and most OP endpoints were generally poor, indicating the inadequacy of mass to represent the health effects of PM2.5. Moreover, weak-to-moderate correlations were observed among different OP endpoints, showing significant differences in the intrinsic mechanisms of these endpoints for exerting oxidative stress, and thus supporting the importance for assessing the integrative OP of PM with several OP endpoints.