Airborne microplastic contamination and health risks in Greater Cairo, Egypt

Air pollution by microplastics (MPs) is an increasingly concerning environmental issue, but the presence of MPs in the atmosphere and its potential health risks has not been studied in Greater Cairo. The sites were therefore selected during the winter season from the north to the south of the Cairo metropolitan area, representing urban and residential/industrial areas in terms of population, traffic, and industrial pressure. This was achieved through a combination of quantitative MP detection, mathematical modeling, and a risk assessment approach based on total suspended particulate matter (TSP) at these sites. The TSP concentration was investigated in the air and associated MP particles. The highest MP values were found at the study sites with higher population and more traffic than at lower locations. The spatial distribution of site concentrations was from high to low. Helwan site (87 particles/m³) had the most MP, followed by Dokki (69 particles/m³) and Nasr City (60 particles/m³), and El-Nozha had the least MP during the investigation (30 particles/m³). The morphology, composition, and size of these MPs in the samples were determined by scanning electron microscopy (SEM) and gas chromatography-mass spectrometry (GC-MS). Various MP forms have been identified in these sites, including fibers, fragments, films, and pellets, with fragments being the most common. Three different MP polymers (PE, PP, and PS) were identified. The potential health risks posed by airborne MPs cannot be ignored when exposed to outdoor airborne substances at maximum annual levels. This study confirms the widespread existence of the inhaled MP in the air and provides a solid basis for future studies aimed at understanding real-world conditions of inhalation exposure to MP.