Microplastic pollution across the Brazilian coastline: Evidence from the MICROMar project, the largest coastal survey in the Global South

Microplastic (MP) pollution in coastal environments poses a significant threat to biodiversity and ecosystem services, with potential implications for human health, particularly in the Global South, where data on large-scale impacts are scarce. As part of the MICROMar project, we conducted the most extensive standardized survey of MPs in tropical beach sediments, analyzing 4134 samples from 1024 beaches along approximately 7500 km of Brazil's coastline. MPs (from 300 μm to <5 mm) were extracted, quantified, and characterized by morphology, color, type, and chemical composition. MP occurrence varied widely across states (16.5 %-90.6 %), with 69.3 % of beaches contaminated. 24,549 MPs, mostly irregular fragments dominated by white, green, and blue colors, were identified. The most common polymers were polyethylene (PE), expanded polystyrene (EPS), and polypropylene (PP), among 21 types of polymers. Concentrations ranged from 0 to 3483.4 MP/kg, with hotspots in Paraná, Sergipe, São Paulo, and Pernambuco. A national baseline of 27.09 MP/kg was estimated. Pollution, hazard, and ecological risk indices identified priority zones. Predictive models revealed that the state, municipality, proximity to sewage discharge, rivers, urbanization, and the Plastic Pressure and Risk Index (PPRI) significantly influenced the distribution of MP. Our findings provide robust scientific support for monitoring and mitigation efforts, offering one of the most comprehensive coastal MP datasets in the Global South.