Atmospheric microplastics deposition assessment in a countryside municipality in Southeastern Brazil: A case study at a state elementary school

The widespread use of plastics has revolutionized modern life, but also led to environmental pollution. Although microplastics (MPs) have been detected in various environments, their presence in the atmosphere, particularly in Brazil, is poorly studied. This research investigated atmospheric MP concentrations at Alvaro Guião School in São Carlos, Brazil, from 2021 to 2022. Outdoor MP concentrations ranged from the limit of detection (LOD) to 168.03 items m−2 day−1, and indoor concentrations ranged from LOD to 60.16 items m−2 day−1. Predominantly, these MPs were fragments, even in the indoor environment, suggesting abundant sources, such as resuspension. Seasonal variations were not observed for outdoor fragments and fibers, nor for indoor fragments. However, indoor fiber concentrations were higher during the dry season (p > 0.05), likely due to winter clothing and reduced ventilation. Fragment sizes were mainly