Searches for the best air quality cities or worst air quality cities often ask for a live AQI answer. This ranking uses a different, more stable measure: annual PM2.5 concentration in micrograms per cubic meter. IQAir's 2025 World Air Quality Report describes PM2.5 data from 9,446 cities across 143 countries, regions, and territories, using data from regulatory monitoring stations and low-cost sensors that IQAir validates, calibrates, and harmonizes. [1]
Data note: These are 2025 annual PM2.5 rankings, not live AQI. Annual PM2.5 can show fine-particle pollution patterns across cities, but it is not a route-level reading, personal exposure measurement, or medical recommendation. Air Quality Router uses estimated AQI, route timing, and freshness labels for planning context inside the app.
Top 10 cleanest cities by annual PM2.5
The cleanest list below reverses the lowest 2025 PM2.5 rows from IQAir's paginated city ranking. IQAir's press kit also names Nieuwoudtville, South Africa, as the world's cleanest city in 2025 with annual average PM2.5 of 1.0 µg/m³. [3] [4]
| Clean-air rank | City | Country or territory | 2025 annual PM2.5 | IQAir global rank | WHO guideline context | Visual |
|---|---|---|---|---|---|---|
| 1 | Nieuwoudtville | South Africa | 1.0 µg/m³ | 9446 | Meets 5 µg/m³ annual guideline | |
| 2 | Utö | Finland | 1.3 µg/m³ | 9445 | Meets 5 µg/m³ annual guideline | |
| 3 | Lihue | USA | 1.4 µg/m³ | 9444 | Meets 5 µg/m³ annual guideline | |
| 4 | Honokaa | USA | 1.4 µg/m³ | 9443 | Meets 5 µg/m³ annual guideline | |
| 5 | Muonio | Finland | 1.4 µg/m³ | 9442 | Meets 5 µg/m³ annual guideline | |
| 6 | Dexter | USA | 1.5 µg/m³ | 9441 | Meets 5 µg/m³ annual guideline | |
| 7 | Hiouchi | USA | 1.5 µg/m³ | 9440 | Meets 5 µg/m³ annual guideline | |
| 8 | Papeete | French Polynesia | 1.5 µg/m³ | 9439 | Meets 5 µg/m³ annual guideline | |
| 9 | Ainaloa | USA | 1.6 µg/m³ | 9438 | Meets 5 µg/m³ annual guideline | |
| 10 | Haines | USA | 1.6 µg/m³ | 9437 | Meets 5 µg/m³ annual guideline |
Clean annual averages do not make every street or hour clean. Smoke, traffic, weather, and local monitoring coverage can change the air on a particular day. A city ranking is a useful starting point, while route planning still needs local source freshness and timing.
Top 10 most polluted cities by annual PM2.5
IQAir's 2025 city table ranks Loni, India, first among the most polluted cities, followed by Hotan, China, and Byrnihat, India. The same press kit notes that the 25 most polluted cities in the 2025 ranking were located in India, Pakistan, and China. [2] [4]
| Pollution rank | City | Country | 2025 annual PM2.5 | WHO guideline context | Visual |
|---|---|---|---|---|---|
| 1 | Loni | India | 112.5 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 2 | Hotan | China | 109.6 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 3 | Byrnihat | India | 101.1 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 4 | Delhi | India | 99.6 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 5 | Faisalabad | Pakistan | 98.8 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 6 | Rahim Yar Khan | Pakistan | 92.6 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 7 | Ghaziabad | India | 89.2 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 8 | Lahore | Pakistan | 88.9 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 9 | Sukkur | Pakistan | 88.6 µg/m³ | Over 10 times the 5 µg/m³ annual guideline | |
| 10 | Ula | India | 86.8 µg/m³ | Over 10 times the 5 µg/m³ annual guideline |
What the rankings can teach
Our World in Data describes air pollution as a major health and environmental problem, with outdoor and indoor pollution linked to several leading causes of death and disease. State of Global Air publishes country-level and city-level air-quality and health-impact resources for broader public-health context. These sources explain why PM2.5 rankings matter, but they do not turn an annual city average into individual advice. [5] [6]
For everyday walking and jogging, the useful lesson is narrower: air quality changes by place and time. A high annual PM2.5 city may still have better and worse hours. A low annual PM2.5 city can still have wildfire smoke, traffic corridors, or stale readings. The app-level job is not to promise a health outcome; it is to keep estimated AQI, timing, route options, and data freshness together before heading out.
Compare cleaner-hour AQI context before a route starts
Before heading out, Air Quality Router compares walking and jogging routes with estimated AQI, route timing, and freshness labels. Download Air Quality Router on the Apple App Store to keep cleaner-hour planning context beside the route decision.
Download on the Apple App StoreSources
- IQAir 2025 World Air Quality Report: annual PM2.5 report scope, units, monitoring-source context, PM2.5 legend, and global city-ranking method.
- IQAir World's most polluted cities: 2025 city table used for the top 10 most polluted annual PM2.5 rows.
- IQAir city ranking final page: lowest 2025 annual PM2.5 city rows used for the top 10 cleanest table.
- IQAir 2025 World Air Quality Report press kit: key findings naming Nieuwoudtville as the cleanest city and Loni as the most polluted city.
- Our World in Data air pollution overview: health and environmental context for air pollution and PM2.5 relevance.
- State of Global Air: global air-quality and health-impact reporting context.
Air Quality Router is an informational planning tool, not medical advice. Personal health decisions belong with qualified care guidance.