Atmospheric dust and air quality over large-cities and megacities of the world

Abstract. According to the United Nations (UN) more than 55 % of the global population resided in urban areas in 2018, a number projected to increase to an estimated 60 % of the world's population by 2030. As urbanization accelerates, degradation of air quality becomes an increasing environmental pressure to human welfare and health. To date, epidemiological studies reveal a strong connection between airborne dust and adverse health effects. This study investigates the fine-mode and coarse-mode dust particulate matter levels within the planetary boundary layer (PBL) over major cities and megacities of the world (population > 5 million), leveraging on the European Space Agency (ESA) – “LIdar climatology of Vertical Aerosol Structure” (LIVAS) multiyear satellite-based dust climate data record. Results show that current dust levels exceed World Health Organization (WHO) annual-mean air quality guidelines (AQGs) for PM2.5 and PM10 in 49.4 % and 87.7 % of the cities considered, respectively, exposing ∼ 700 million people to hazardous dust concentrations. Moreover, according to the outcomes of the study, this number is expected to increase to ∼ 850 million individuals (∼ 22 % increase) by 2030s, though due to the general declining dust tendencies the health hazard is projected to be diminished in severity. Particularly affected are cities in the regions of Middle East, Indian subcontinent, East Asia, North Africa, and the Sahel. Epidemiological models are employed to estimate associated health risks. The study provides an informative mitigation and adaptation tool to support observational-based policymaking, air quality management, and public health planning to protect human health in the context of accelerating urbanization.