Long-term spatiotemporal trends and population-weighted exposure to PM2.5 in Greater Cairo (2000–2020)

Fine particulate matter (PM₂.₅) pollution poses significant environmental and health risks in urban areas, such as Greater Cairo (GC). To provide the first high-resolution, two-decade assessment (2000–2020) of chronic exposure, this study integrates 1 km satellite-derived PM₂.₅ concentrations with comprehensive population distribution dynamics (LandScan Global). Trends were assessed using the Mann–Kendall test, and Sen’s slope was also calculated. We utilized advanced exposure metrics: the Population-Weighted Mean Concentration (PWMC) and Total Exposure (TE). A multi-level classification based on the five World Health Organization (WHO) Interim Targets and Guideline Value (IT-1, IT-2, IT-3, IT-4, and the Guideline of 5 µg/m³) was used to quantify the health significance of exposure evolution rigorously. PWMC consistently violated strict international health standards, remaining 7 to 10 times higher than the WHO Guideline (5 µg/m³) over the entire period, indicating a 100% population exposure risk. Concentrations exhibited a non-linear temporal pattern, peaking around 2010 (domain-averaged peak at 45.6 µg/m³) before showing a decline through 2020. Crucially, analysis revealed that high population growth increased the overall health burden (TE), actively counteracting localized improvements in pollution intensity (PWMC). Robust K-means clustering confirmed that the highest exposure burdens persisted in dense urban cores and industrial corridors. These findings provide quantitative evidence essential for targeted air quality management, demonstrating the urgent need for integrated urban planning and localized policies to reduce the cumulative health burden in this megacity.