Abstract:

Reactive oxygen species (ROS) are key drivers of adverse health impacts of airborne particulate matter (PM), yet their concentrations and reactivity from different emission sources remain poorly understood. Deposition of ROS in the lungs can lead to oxidative stress and a variety of health effects. ROS can be formed through redox cycling from environmentally persistent free radicals (EPFRs), which are long-lived radicals. Using electron paramagnetic resonance (EPR) spectroscopy, this work characterizes the formation of ROS and EPFRs in PM from biomass burning in sub-arctic regions, and from non-exhaust emissions. Studying wintertime pollution in cities such as Fairbanks is particularly important because it represents regions where prolonged wintertime pollution and indoor air quality challenges pose distinct public health risks. Non-tailpipe emissions are emerging as a dominant pollution source of traffic PM due to increased vehicle electrification and lack of regulations surrounding them. The first study examines ROS and EPFR formation in outdoor and indoor PM in wintertime Fairbanks, Alaska. Oxidative potential, which is used as a health relevant metric, was also assessed using multiple acellular assays. The second study discusses radical formation from laboratory‑generated brake wear particles under different braking regimes. The third study explores EPFR and ROS formation from PM samples collected along freeways in Long Beach and Santa Ana, California, and compares them to laboratory-generated brake wear particles, road dust, and tire-tread samples. Together, these studies offer source-specific insight into radical formation and oxidative potential from ambient and non-tailpipe PM, helping understand their health-relevant properties.