The changing PM2.5 dynamics of global megacities based on long-term remotely sensed observations

Abstract

Satellite observations show that the rapid urbanization and emergence of megacities with 10 million or more residents have raised PM2.5 concentrations across the globe during the past few decades. This study examines PM2.5 dynamics for the 33 cities included on the UN list of megacities published in 2018. These megacities were classified into densely (>1500 residents per km2), moderately (300–1500 residents per km2) and sparsely (35 μg/m3). In 2016, the least polluted megacity was New York and most polluted megacity was Delhi whose average annual PM2.5 concentration of 110 μg/m3 is nearly three times the WHO’s non-attainment threshold.

Keywords

• Megacities
• Gridded population counts
• Remotely sensed PM2.5 concentrations
• Pollution burden