Bangladesh, Pakistan and India exceed the maximum annual concentration of PM₂,₅ set by the World Health Organization by more than ten times. Only seven of the 127 countries in the world analyzed by the Swiss IQAir company complied in 2023 with the new safety limits for suspended particles less than 2.5 microns in diameter.

These particles are linked in part to fossil fuels and which are linked to around one million premature deaths each year in the World. The study also classifies capital cities based on poor air quality.