Microplastics in the indoor air of subway station in Istanbul

Microplastics (MPs) have emerged as significant airborne pollutants, yet their presence in enclosed public transport environments remains understudied. This research investigates the occurrence, characteristics, and potential human exposure to MPs in the indoor air of a subway station in Istanbul. Airborne MPs were collected using both passive deposition and active air sampling methods for deposited and airborne MPs, respectively over seven days at a high-traffic metro station. Deposited MP concentrations ranged from 278,571 to 865,714 MPs/m²/day, while airborne MP concentrations varied between 0.4 and 2.93 MPs/m³. Inhalation exposure estimates indicate that passengers in different age groups may inhale between 0.24 and 0.30 MPs during a 15-minute wait on the platform. Microscopic and Raman spectroscopy analyses revealed that over 70% of MPs were fibers, predominantly composed of polyethylene (PE, 25%) and polyethylene terephthalate (PET, 21%). The majority of airborne MPs measured < 100 μm, whereas deposited MPs were predominantly 200–400 μm in size. These findings underscore the presence of MPs in enclosed transport systems and their potential contribution to indoor air pollution. Given the widespread public reliance on subway transport, further studies are necessary to assess the health risks associated with chronic inhalation of MPs and to develop mitigation strategies for reducing indoor MP exposure.