Novel Approach to Assess the Toxicity of PM 2.5 on a Subway Platform Using a Mobile Air–Liquid Interface System and Submerged Exposure

High Resolution Image Download MS PowerPoint Slide Subway stations are enclosed environments that can have elevated concentrations of PM 2.5 (particulate matter with an aerodynamic diameter of <2.5 μm). These particles are primarily generated by mechanical wear from trains and are therefore rich in transition metals and suspected to affect health upon inhalation. To simulate real-world inhalation scenarios, this study aimed to assess the toxicity of airborne subway PM 2.5 using a mobile air–liquid interface (ALI) exposure system directly on the platform, using monoculture (A549) and coculture (A549 + dTHP-1) cell models, alongside laboratory submerged exposures. In ALI exposures, a dose of 0.12 ± 0.07 μg/cm 2 could not induce any change in cell viability or inflammatory markers after 24 h of incubation. In submerged experiments, a higher dose was applied than in ALI, inducing a decrease in cell viability in both A549 and dTHP-1 cells. A549 cells exhibited increased IL-6 and TNF-α release at the highest dose (100 μg/mL). In dTHP-1 cells, IL-8 release was significantly elevated even at the lowest dose (10 μg/mL), and all four cytokines (IL-8, IL-6, IL-1β, and TNF-α) were significantly increased at 100 μg/mL. These findings highlight the critical role of exposure conditions in toxicological studies and support the use of both in situ and laboratory-based approaches. Moreover, longer in situ exposures may be necessary to achieve doses comparable to those in a laboratory setup for comparison.