Association of PILS-based and filter-based particle-bound reactive oxygen species with urban nanoparticles, secondary organic aerosols, and in-vitro oxidative responses

Exposures to fine particulate matter (PM1) have been associated with health impacts, but our understanding of PM1 concentration–response (PM1-CR) relationships remains incomplete. This study investigates the association between particulate-bound reactive oxygen species (PB-ROS) and cellular oxidative stress responses induced by urban nanoparticles. PB-ROS were measured using the DCFH assay, both on PTFE filters (24-hour resolution, PB-ROSfilter) and PB-ROS measured using a Particle-Into-Liquid Sampler (2-hour resolution, PB-ROSPILS). We compared these with oxidative stress markers in BEAS-2B human cell lines exposed directly to ambient air at the air–liquid interface. A comparative analysis of PB-ROSfilter and PB-ROSPILS revealed significant differences in the types of PB-ROS detected, mainly due to the temporal resolution of sampling and the measurement techniques. In most cases, PB-ROSfilter levels were reduced by more than 90% compared to PB-ROSPILS. PB-ROSfilter predominantly identified long-lived species, which are more stable and indicative of aged aerosols. In contrast, PB-ROSPILS provided insights into transient PB-ROS, which correlated with urban nanoparticles. A low condensation sink played a decisive role, suggesting atmospheric conditions in which condensable compounds (including ROS) did not rapidly deposit onto pre-existing accumulation-mode particles but instead bound to nanoparticles. Finally, we demonstrate that gene expression patterns for oxidative stress in BEAS-2B human cell lines correlate with PB-ROSPILS, but not with PB-ROSfilter.