Exposure to fine particulate matter (PM1) has been associated with health impacts, but understanding PM1 concentration–response (PM1-CR) relationships remains incomplete, especially at low PM1 levels. Here, we present data related to the RHAPS experiment carried out in the Po Valley in 2019 [Costabile et al., 2023].

This study investigated the association between particle-bound reactive oxygen species (PB-ROS) and in vitro pro-oxidative responses. To mimic exposure of the lungs to ambient air, we employed an Air–Liquid Interface (ALI) model using cultures of human bronchial epithelial cells (BEAS-2B). PB-ROS were measured using the DCFH assay via two approaches: offline 24-hour resolution measurements from PTFE filters (PB-ROS_filter) and semi-continuous (2-hour resolution) measurements using a Particle-Into-Liquid Sampler (PILS) (PB-ROS_PILS).

A comparative analysis of the PB-ROS_filter and PB-ROS_PILS measurements showed significant differences in the types of ROS detected, primarily driven by the sampling resolution. The PB-ROS_filter measurements predominantly identified long-lived species, which are more stable and indicative of aged aerosols, associated with secondary organic aerosols (SOAs). In contrast, PB-ROS_PILS measurements revealed transient PB-ROS related to urban nanoparticles, which are abundant during the day due to traffic emissions and photochemical processes. Statistically significant correlations suggest that transient PB-ROS are influenced by fresh traffic nanoparticles, with the Condensation Sink (CS) playing a decisive role in their persistence in the atmosphere. The CS having a low value indicates atmospheric conditions in which condensable compounds (including ROS) do not sink rapidly into pre-existing accumulation-mode particles and may form nanoparticles [Costabile et al., 2023].

Finally, this study highlights a positive correlation between the mass-normalized PB-ROS_PILS and oxidative stress gene expression, underscoring the potential health implications of short-lived ROS. Limitations of this study relate to the limited temporal coverage of the PILS and the absence of fully online ROS detection methods for characterizing highly reactive species, which may pose immediate health risks in urban environments with fresh emissions.