The air in London, Beijing, San Francisco — and 16 other cities — is measurably, substantially cleaner than it was a decade ago. A major new study published in March 2026 by Breathe Cities and the C40 Cities network documented reductions of more than 20% in two of the most harmful pollutants since 2010, with some cities cutting toxic air by nearly half.
The analysis examined air quality trends across nearly 100 cities between 2010 and 2024, identifying 19 cities that achieved remarkable reductions in both fine particulate matter (PM2.5) and nitrogen dioxide (NO2).
The Numbers
Beijing led with a 48% cut in PM2.5 — the most dramatic transformation. The Chinese capital was once synonymous with toxic smog so thick schools closed and residents wore masks. The improvement comes from coal-fired heating plants replaced, older vehicles scrapped, and electric vehicles rolled out at unprecedented scale.
London cut NO2 by 38% and PM2.5 by 28%, primarily through the Ultra Low Emission Zone, expanded cycling infrastructure, and phasing out diesel buses.
San Francisco was the only US city in the 19 to achieve cuts over 20% in both pollutants, thanks to California emission standards and aggressive electrification incentives.
The Policy Playbook
What actually worked across all 19 cities: restricting the most polluting vehicles, expanding cycling and walking infrastructure, transitioning public transport to electric or hydrogen, and investing in district heating to replace individual gas boilers.
"Cities can achieve what was once thought impossible: cutting toxic air pollution by 20-45% in a little over a decade," said Cecilia Vaca Jones, executive director of Breathe Cities.
Air pollution kills an estimated 6.7 million people annually worldwide. The 80 other cities in the study that have not yet achieved the same reductions have a clear blueprint now.
Sources: Breathe Cities, C40 Cities, The Guardian (March 12, 2026)
