Role of meteorological variables in shaping airborne microplastic concentrations: Evidence from two metropolitan areas in Brazil

Airborne microplastics (MPs) are emerging atmospheric contaminants of growing environmental and health concern. However, knowledge gaps persist concerning their abundance, sources and drivers across many regions, including Latin America. This research targets this gap by reporting MP data collected using filter-based measurements in two Brazilian cities (Curitiba and Londrina) characterised by distinct socio-economic and environmental profiles. MPs were identified by optical microscopy and μ-FTIR, with their heterogeneity quantified using the Microplastic Diversity Integrated Index (MDII). Mean MP concentrations (number per m 3 , expressed as n/m 3 ) exhibited marked differences, between 0.14 and 0.54 n/m 3 in Curitiba (mean ± SD: 0.32 ± 0.14 n/m 3 ) and 1.26–37.13 n/m 3 in Londrina (9.70 ± 11.40 n/m 3 ). The Mann–Whitney test revealed that meteorological conditions differed significantly between the cities: Londrina was drier, warmer and windier than Curitiba. The intercity disparity in MP concentrations suggests that higher rainfall in Curitiba likely enhanced particle removal. Spearman correlation analysis revealed significant positive correlations between MP concentrations and air temperature and pressure, indicating that thermal turbulence likely facilitated particle resuspension. In contrast, MP correlations with wind speed, relative humidity and rainfall were not statistically significant. Fragments (74–79%) and fibres (21–26%) were the primary morphologies, with sizes predominantly <100 μm in both cities. Main petrochemical MPs were polyethylene in Curitiba (65%) and polyamide in Londrina (61%). MP diversity was higher in Londrina (MDII: 0.54) than in Curitiba (MDII: 0.47), driven by broader polymeric and size distributions. These results highlight that even within the same region, contrasting weather patterns can lead to divergent plastic footprints.