Oxidized and Unsaturated: Key Organic Aerosol Traits Associated with Cellular Reactive Oxygen Species Production in the Southeastern United States

Exposure to ambient fine particulate matter (PM2.5) is associated with millions of premature deaths annually. Oxidative stress through overproduction of reactive oxygen species (ROS) is a possible mechanism for PM2.5-induced health effects. Organic aerosol (OA) is a dominant component of PM2.5 worldwide, yet its role in PM2.5 toxicity is poorly understood due to its chemical complexity. Here, through integrated cellular ROS measurements and detailed multi-instrument chemical characterization of PM in urban southeastern United States, we show that oxygenated OA (OOA), especially more-oxidized OOA, is the main OA type associated with cellular ROS production. We further reveal that highly unsaturated species containing carbon-oxygen double bonds and aromatic rings in OOA are major contributors to cellular ROS production. These results highlight the key chemical features of ambient OA driving its toxicity. As more-oxidized OOA is ubiquitous and abundant in the atmosphere, this emphasizes the need to understand its sources and chemical processing when formulating effective strategies to mitigate PM2.5 health impacts.

Automated summary

Exposure to PM2.5 is associated with millions of premature deaths annually. The overproduction of reactive oxygen species (ROS) through oxidative stress is a possible mechanism for PM2.5-induced health effects. In this study, the authors found that oxygenated organic aerosol (OOA), particularly more-oxidized OOA, is the main type of organic aerosol associated with cellular ROS production. They also identified highly unsaturated species with carbon-oxygen double bonds and aromatic rings in OOA as major contributors to cellular ROS production. These findings highlight the importance of understanding the sources and chemical characteristics of ambient OA in formulating strategies to mitigate the health impacts of PM2.5.