Chemical, Oxidative, and Toxicological Profiles of Fine Ambient Particulate Matter in Alaska
OLUCHI NWEKE, P. S. Ganesh Subramanian, Sudheer Salana, Anastasia Hewitt, Raghu Betha, Vishal Verma, University of Illinois, Urbana Champaign
Abstract Number: 192
Working Group: Health-Related Aerosols
Abstract
Oxidative potential (OP) is a metric that quantifies the ability of particulate matter (PM) to induce oxidative stress in humans and is widely used as a surrogate for PM toxicity. During winter, surface-based temperature inversions due to low solar insolation in Alaska, limits the dispersion of PM2.5, predominantly emitted from residential wood-burning, and leads to higher ambient PM2.5 concentrations. However, currently, there is limited research on the health effects and toxicological properties of Alaskan PM2.5. In this study, we quantified the chemical composition and OP of PM2.5 collected in the City of North Pole, Alaska during winter 2022–23 and compared them with wintertime PM2.5 from the Midwest US. We evaluated the toxicity of PM2.5 using four different metrics: 3 acellular OP endpoints — dithiothreitol (OPDTT), glutathione (OPGSH), and hydroxyl radical generation (OPOH), and 1 cellular endpoint — cytotoxicity (CT) in A549 cells using crystal violet assay.
Our results revealed that wintertime ambient PM2.5 concentrations in Alaska (39.1 μg/m3) were 223.1% higher than Midwest USA (12.1 μg/m3). The water-soluble and water-insoluble organic carbon (WSOC and WIOC) fractions in wintertime Alaskan PM2.5 (17.0% and 13.3%, respectively) were 2 to 4 times that of Midwestern PM2.5. However, the elemental carbon (EC) fractions in Alaska (3.2%) were similar to the Midwest. The average OPDTT, OPGSH, and OPOH in Alaskan were 33.1±6.9, 18.7±6.4, and 0.14±0.12 pmol/(min.μg), respectively, translating to 1.68, 2.54, and 0.38 times of those reported for Midwestern PM2.5. The average CT levels were also 60% higher in Alaska (2.68%/μg) compared to the Midwest (1.69%/μg). Strong intercorrelations (r > 0.4) were observed among the different endpoints, except between OPOH and CT. Both OC and EC were strongly correlated (r > 0.5) with OPDTT, OPGSH and CT, but metals were not correlated (r < 0.1) with any of the OP assays. Collectively, these results indicate that the higher carbon fraction in Alaskan PM2.5 may be driving its OP and could possibly explain the higher intrinsic OP in Alaska, as compared to the Midwest US, necessitating further research into the toxicological properties of air pollutants and subsequent health effects in Alaska.