| Summary: | Indoor and outdoor air pollution is related to adverse human health effects, especially in children due to their ongoing physical development. This study assesses airborne microplastics (MP) concentrations and associated inhalation risks in a school in Estarreja, Portugal, near a large industrial complex producing polyvinylchloride (PVC). PM10 samples were collected over two campaigns (winter and spring) in four classrooms (ages 3–11 years) and adjacent outdoor areas. Airborne MP were determined by pyrolysis–gas chromatography coupled to Orbitrap-mass spectrometry (Pyr-GC-Orbitrap-MS) targeting ten common polymers. Six polymers, including polymethyl methacrylate, nylon-6,6, polypropylene, nitrile butadiene rubber, polyvinyl chloride and polystyrene were identified. Indoor MP average concentrations (21.8 ± 16.3 ng/m3, n = 35) were significantly higher than outdoor levels (13.4 ± 13.6 ng/m3, n = 36). Seasonal differences were observed, with higher MP concentrations in spring compared to winter. Based on the concentrations detected indoors, the daily inhalation dose was evaluated and revealed a median daily exposure to MP in children of 1.57 ± 0.93 ng kg bw-1 d-1. Additionally, a non-targeted chemometric method using Regions of Interest-Multivariate Curve Resolution-Alternating least squares (ROIMCR) identified co-occurring pollutants such as phthalates, pesticides, and nicotine. This is the first study to apply Pyr-GC-Orbitrap-MS combined with ROIMCR for simultaneous targeted and untargeted analysis of airborne MP in a school setting. The findings reveal continuous exposure of children to a complex mixture of MP and hazardous additives, emphasizing the need to include these compounds in indoor air quality assessments and to protect sensitive populations in educational environments.
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