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 day, and indoor concentrations ranged from LOD to 60.16 items m day. 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 <60 μm, while fibers ranged from <60 μm to 3000-5000 μm. Polyester was the primary MP component (83-100% outdoors and 29-100% indoors), followed by ethylene vinyl acetate (EVA, 0-17% outdoors and 0-57% indoors), common in synthetic clothing and school supplies, respectively. Other plastics, found in packaging and bottles, like polyethylene (0-14%) and polyethylene terephthalate (0-6%), were also identified indoors. This study not only enhances the current understanding, but also pioneers analyses within a school environment. Despite being a work in progress, this study has already shown the presence of plastic particles in environments where children, one of the most susceptible groups to air pollution, spend a significant portion of their time. Furthermore, it can assist in developing an assessment of acceptable levels and guidelines.