Spatial analysis and potential exposure implications of microplastic contamination in urban street dust in Urmia

Microplastics (MPs) are ubiquitous environmental contaminants detected across water, air, and soil, posing a major threat to organisms and presenting a critical global ecosystem challenge. This study assesses microplastic contamination in the street dust of Urmia city, Iran. Samples were collected from various points across the city to investigate the microplastic concentration, physical characteristics, and polymer composition. The results showed that microplastic concentration in Urmia's street dust ranged from 500 to 17,000 particles per kilogram, indicating a high level of pollution. The most common form of MPs found were fibers, with a predominant size between 100 and 500 micrometers. In terms of color, transparent (40%) and black (22%) microplastics were the most abundant types. Scanning Electron Microscope (SEM) analysis of the particles revealed irregular shapes and rough surfaces, which are typical signs of physical and mechanical degradation processes like fragmentation and weathering. The polymer composition was determined by µ-Raman, revealing common types such as PS, POM, PES, PET, PE, PP, EP and PVC. Finally, the potential exposure of microplastic ingestion were analysed. Based on the estimations, an adult in a normal scenario ingests between 37 and 1150 particles annually, while in an acute scenario, this number can reach up to 2894 particles. The observed high contamination levels, fiber predominance, and greater estimated ingestion exposure in children highlight significant microplastic presence in Urmia street dust, emphasizing the importance of local mitigation strategies and further exposure research.