Indoor aerosol dynamics, composition, and pathway-specific biological responses in human bronchial epithelial cells (BEAS-2B) at Rome Fiumicino International Airport (OASIS Project)

Indoor air pollution is a critical public health concern, with fine and ultrafine particulate matter inducing oxidative stress, inflammation, and xenobiotic responses in the respiratory system. The Optimizing Air Safety in Indoor Spaces (OASIS) project applies an innovative integrated framework combining biotag-based droplet mapping, real-time monitoring of indoor air pollutants and environmental parameters, with the direct exposure of air–liquid interface-grown human bronchial epithelial cells (BEAS-2B) using the portable Cultex®-RFS system. This multidisciplinary approach links aerosol dynamics, spatial dispersion, and event-driven air quality variations with pathway-specific cellular responses in a complex indoor environment selected for the campaign at Rome Fiumicino International Airport.Aerosol characterization includes gravimetric mass concentration of airborne Particulate Matter (PM10, PM2.5 and PM1), particle number size distribution, and black carbon (BC), measured using PM samplers, Optical Particle Counters, and multi-wavelength aethalometer, respectively. Indoor micro-meteorological parameters including temperature, pressure and humidity, were measured using reliable off-the-shelf sensors integrated into a cloud- and edge-based IoT platform, enabling identification of event-related indoor air quality degradation and assessment of the impacts of routine actions, such as opening/closing a door or window.To track the movement and dispersion of droplets within the indoor space, an advanced technique based on identifiable genomic sequences (Biotag) was applied to the monitored indoor space. This revealed localized hotspots of droplet persistence and concentration near the Cultex exposure module, aerosol instruments, heating, ventilation and air conditioning (HVAC) outlets, indicating that airflow patterns and instrument-induced turbulence strongly influence inhalation exposure.The toxicological response was characterised in BEAS-2B cells undergoing 24h exposure to the monitored indoor environment (for a total of 15 exposures over the period May-December 2025), and assessed by quantitative real-time PCR of genes involved in oxidative stress (HMOX1, NQO1, SOD1, SOD2, NFE2L2), xenobiotic response (AHR, CYP1A1, CYP1B1) and inflammation (IL-1β, IL-6, IL-8, IL-18, TNF-α, NLRP3). Pathway-specific biological indices were calculated as the mean standardized fold-change of genes within each pathway. Correlation analyses revealed PM size- and composition-dependent responses, with the xenobiotic response index positively associating with 0.25–0.50 µm particle number (Spearman ρ = 0.59, p = 0.024), PM2.5 mass (ρ = 0.66, p = 0.009), PM₁ mass (ρ = 0.61, p = 0.017), and black carbon (ρ = 0.57, p = 0.030). Oxidative stress and inflammatory indices exhibited more variable associations, suggesting preferential activation of xenobiotic pathways by fine, combustion-derived particles.Overall, the OASIS project provides a comprehensive mechanistic understanding of indoor aerosol behaviour and related cellular responses, integrating aerosol dynamics, spatial dispersion and pathway-specific biological effects. The results show that indoor exposure patterns and biological responses are shaped not only by indoor sources and airflow regimes, but also by outdoor air pollution infiltrating the indoor environment, particularly fine and combustion-derived particles. These findings underscore the importance of integrated indoor–outdoor air quality monitoring and targeted mitigation strategies to protect occupational and public health in complex indoor environments, supporting timely, evidence-based interventions to promote healthier indoor conditions.