Atmospheric Dust and Air Quality over large-cities and megacities of the World

Abstract. Urbanization is accelerating, with over 55 % of the global population residing in urban areas as of 2018, projected to reach 60 % by 2030. This growth intensifies environmental pressures, notably air quality degradation, which adversely affects human health and socioeconomic systems. Among air pollutants, atmospheric mineral dust plays a critical role in Earth’s climate system and poses direct health risks. This study assesses the mass concentration of atmospheric dust within the planetary boundary layer (PBL)—the atmospheric region where most anthropogenic activity occurs—across global large cities and megacities (population >5 million). Using the European Space Agency’s LIdar climatology of Vertical Aerosol Structure (LIVAS) climate data record, which offers multiyear, four-dimensional Earth Observation-based dust mass concentration data, we analyze both fine-mode and coarse-mode dust components. Results show that current dust levels exceed World Health Organization (WHO) annual mean air quality guidelines (AQGs) for PM_2.5 and PM₁₀ in 49.4 % and 87.7 % of urban areas studied, respectively, exposing approximately 701.4 million people to hazardous dust concentrations. Regions particularly affected include the Middle East, Indian subcontinent, East Asia, North Africa, and the Sahel. Projections indicate a 21.7 % increase in the exposed population by 2030, totaling 856.5 million, despite a general decline in dust severity in over 70 % of cities. Epidemiological models are employed to estimate associated health risks. This work provides essential insights for evidence-based air quality management and public health strategies, supporting mitigation efforts in the face of urban expansion and climate change.