Air Quality Assessment in Iran During 2016–2021: A Multi-Pollutant Analysis of PM2.5, PM10, NO2, SO2, CO, and Ozone

Air pollution has emerged as one of the most critical public health challenges globally, with an astonishing 96% of the world’s population breathing air below the health standards. This study investigates the amount and distribution of six major air pollutants, PM10, PM2.5, O3, SO2, NO2, and CO, at numerous air monitoring stations across Iran from 2016 to 2021. The primary objectives were to identify the cities with the highest pollution levels, and to assess the spatiotemporal evolution of air pollution across the country, aiming to provide a comprehensive overview and climatology of air quality. The results indicate that cities such as Zabol and Ahvaz consistently rank among the most polluted, with annual average PM10 concentrations exceeding 190 µg m−3 and PM2.5 reaching alarming levels up to 116.7 µg m−3. Furthermore, O3 and SO2 amounts were high in Zabol too, classifying it as the most polluted city in Iran. In addition, Tehran exhibits high NO2, SO2, and CO concentrations due to high industrial activity and vehicular emissions. Seasonal analysis reveals significant variations in pollutant levels, with PM concentrations peaking during specific months over various parts of the country, particularly driven by local and distant dust events. By integrating MERRA-2 reanalysis pollution data and ground measurements, this research provides a robust framework for understanding pollution dynamics, thereby facilitating more effective policy-making and public health interventions. The results underscore the necessity for immediate action to mitigate the adverse effects of air pollution on public health, particularly in areas prone to industrial activities (i.e., Tehran, Isfahan) and dust events (Zabol, Ahvaz).