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Key Findings

  • Only 14% of global cities met the World Health Organization (WHO) annual PM2.5 guideline of 5 µg/m³, down from 17% the previous year.
  • Only thirteen countries and territories met the WHO annual PM2.5 guideline: French Polynesia, Puerto Rico, U.S. Virgin Islands, Barbados, New Caledonia, Iceland, Bermuda, Réunion, Andorra, Australia, Grenada, Panama and Estonia.
  • 130 out of 143 countries, regions and territories (91%) did not meet the WHO annual PM2.5 guideline value.
  • The five most polluted countries were Pakistan (67.3 µg/m³), Bangladesh (66.1 µg/m³), Tajikistan (57.3 µg/m³), Chad (53.6 µg/m³) and the Democratic Republic of the Congo (50.2 µg/m³).
  • Loni, India, was the most polluted city, recording an annual average PM2.5 concentration of 112.5 µg/m³ - a nearly 23% increase from 2024 and more than 22 times the WHO guideline.
  • Nieuwoudtville, South Africa, was the world’s cleanest city, with an annual average PM2.5 concentration of 1.0 µg/m³.
  • The world’s 25 most polluted cities were all located in India, Pakistan and China, with India home to three of the four most polluted.
  • The most polluted major U.S. city was El Paso, Texas. Southeast Los Angeles, California was the most polluted region in the United States. Seattle, Washington was the cleanest major U.S. city.
  • 2025 marked the second consecutive year in which no cities in East Asia met the WHO PM2.5 guideline. Pollution patterns in China indicate a westward shift in elevated concentrations.
  • Europe saw mixed air pollution trends in 2025, with 23 countries recording higher PM2.5 concentrations and 18 seeing declines, while winter wood burning, summer transboundary smoke from Canadian wildfires and Saharan dust worsened seasonal pollution.
  • In Latin America and the Caribbean, air quality trends were largely positive: 208 cities recorded decreases in annual PM2.5 concentrations, 95 increased and nine remained unchanged.
  • Oceania remained one of the world’s cleanest regions with 61% of cities meeting the WHO guideline, though record-breaking cold in New South Wales, Australia in June 2025 led to seasonal PM2.5 spikes.

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