Every breath matters. But for most people on earth, every breath also carries a hidden cost. The IQAir 2025 World Air Quality Report, released this year by Swiss-based air quality technology company IQAir, paints a stark picture of a planet still struggling to clean up its act. Covering 9,446 cities across 143 countries, regions and territories , the most comprehensive dataset in the report's history, it finds that only 14% of cities worldwide met the World Health Organisation's annual air quality guideline for PM2.5 in 2025, down from 17% in 2024. PM2.5 refers to tiny particles in the air, smaller than the width of a human hair, that can enter the bloodstream and damage the heart, lungs and brain.
