Pakistan had the most polluted air in the world overall in 2025, and Delhi was the most polluted capital for the seventh time in the last eight years of reporting by the Swiss-based IQAir.  A town bordering India’s capital is the world’s most polluted place. Despite covering nearly 9,500 cities, pollution data gaps leave millions of people exposed to unhealthy air out of the count.

Air pollution worsened in 2025, with the share of cities globally that met the World Health Organisation’s guideline of safe air quality falling to 14% from 17% the previous year. Progress on air quality progress stalled as wildfire smoke and climate change intensified air pollution concentrations, accordinig to the latest global ranking report by IQAir, released today. 

The report by the Swiss-based air quality technology firm ranked 143 countries and territories, as well as almost 9,500 cities by annual average PM2.5 levels, drawn from a continuous real-time data base, accessible to users worldwide.  

It also flags vast data gaps, especially in Africa and West Asia, which saw setbacks in air quality monitoring coverage last year. One particular blow was the Trump administration’s decision to halt the public reporting on air quality from US Embassy and Consulate locations worlwide in March 2025, depriving many cities of their trusted primary data source. As a result, monitoring efforts in 44 countries were weakened, and six were left without any monitoring, according to the new IQAir report.