To rank the most air-polluted countries in the world, we consulted the IQAir World Air Quality Ranking. This database provided us with a list of countries and information on the annual average measured concentration of particulate matter (PM2.5). PM2.5 is widely available and considered the most hazardous air pollutant impacting human health. PM2.5 is measured by micrograms per cubic meter (µg/m³). We used data available for the latest year in their dataset, which is for the year 2022.