25 Least Polluted Cities in the World (2021 Rankings)

Air pollution is one of the leading causes of death around the world. Therefore you may be curious: “What are the least polluted cities in the world?”. Or which country has the least amount of air pollution? Smart Air analyzed 2021 air pollution data from 540 major cities spanning 182 countries in the world to create the 2021 ranking of the “25 Least Polluted Cities in the World”. So, which cities and countries had the cleanest air?

Rankings: 25 Cities with the Cleanest Air in the World

WATCH: Top 5 Least Polluted Cities, 2021

5 Things You Should Know about PM2.5 Air Pollution

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Read on for the full list of 25 cities and an analysis of what this data means.


1. Zurich, Switzerland (0.51 µg/m3)

Zurich Switzerland one of least polluted cities in the world

2. Hobart, Australia (2.73 µg/m3)

Hobart Australia one of least polluted cities in the world

3. Reykjavik, Iceland (3.68 µg/m3)

Rekjavik Iceland one of least polluted cities in the world

4. Launceston, Australia (3.68 µg/m3)

Launceston, Australia, one of least polluted cities in the world

5. Honolulu, US (4.04 µg/m3)

Honolulu, US, one of least polluted cities in the world

6. Vitoria, Brazil (4.10 µg/m3)

Vitoria, Brazil, one of least polluted cities in the world

7. Bergen, Norway (4.39 µg/m3)

Bergen, Norway, one of least polluted cities in the world

8. Wollongong, Australia (4.48 µg/m3)

Wollongong, Australia, one of least polluted cities in the world

9. Turku, Finland (4.51 µg/m3)

Turku, Finland, one of least polluted cities in the world

10. Funchal, Portugal (4.51 µg/m3)

Funchal, Portugal, one of least polluted cities in the world

11. Edinburgh, Scotland (4.62 µg/m3)

Edinburgh Scotland one of least polluted cities in the world

12. Upsala, Sweden (4.70 µg/m3)

Upsala, Sweden, one of least polluted cities in the world

13. Halifax, Canada (4.74 µg/m3)

Halifax, Canada, one of least polluted cities in the world

14. Trondheim, Norway (4.77 µg/m3)

Trondheim, Norway, one of least polluted cities in the world

15. Castellón de la Plana, Spain (4.79 µg/m3)

Castellón de la Plana, Spain, one of least polluted cities in the world

16. Tampere, Finland (4.98 µg/m3)

Tampere, Finland, one of least polluted cities in the world

17. Adelaide, Australia (5.05 µg/m3)

Adelaide, Australia, one of least polluted cities in the world

18. Vancouver, Canada (5.06 µg/m3)

Vancouver Canada one of least polluted cities in the world

19. Glasgow, Scotland (5.07 µg/m3)

Glasgow, Scotland, one of least polluted cities in the world

20. Oulu, Finland (5.13 µg/m3)

Oulu, Finland, one of least polluted cities in the world

21. Brisbane, Australia (5.19 µg/m3)

Brisbane, Australia, one of least polluted cities in the world

22. Gothenburg, Sweden (5.26 µg/m3)

 Gothenburg, Sweden, one of least polluted cities in the world

23. Surrey, Canada (5.30 µg/m3)

Surrey Canada one of least polluted cities in the world

24. Sydney, Australia (5.34 µg/m3)

Sydney, Australia, one of least polluted cities in the world

25. Newcastle, Australia (5.36 µg/m3)

Newcastle, Australia, one of least polluted cities in the world

Read More: The 25 Most Polluted Cities of 2021?

Analysis

Of the 25 least polluted cities in the world with the best air quality, Nordic countries (Finland, Sweden, Norway, Iceland) dominated the rankings. 8 out of the 25 cities with the best and cleanest air were Nordic countries. Australia topped the list as least polluted country in the world, with 7 cities in the top 25. Switzerland is ranked as one of the least polluted countries in the world. Australia, Canada, and Finland were the only countries having at least 3 cities ranking in the top 25 cities with the cleanest, least polluted air.

Comparing with the previous year, Australian cities saw an improvement in rankings with only 2 cities in 2020 to 7 in 2021. On the other hand, Nordic countries saw a drop in the number cities from 10 to 8. Zurich, Switzerland, remains top on the list for both years.

Even though these are some of the cities with the best air quality in the world, each city experienced times during 2021 where pollution was over the WHO recommended limit. Only 16 out of 25 of these cities met the new WHO air quality guidelines (AQG) levels of 5 µg/m3. This shows how serious air pollution is all across the world. There is also research that even little amounts of pollution such as those typically present in these least polluted cities can have an impact on health.

Below is a pollution heat map from the WHO. WHO research shows that over 92% of people in the world are breathing unsafe air with high air pollution levels.

Global Air Pollution Map
Image: WHO

How Air Pollution Was Measured to Find Least Polluted Cities in World

There are various pollutants (both particles and gases) that can be found in the air. One of the most commonly tracked pollutants are very small, fine particles called PM2.5.

These small pollutants are under 2.5 micrograms in width and considered to be one of the more dangerous pollutants due to their ability to enter deep into the lungs and bloodstream. The above rankings of the least polluted cities in the world were ranked based on their 2021 average PM2.5 pollution levels.  

Open Data

As part of Smart Air’s open data pledge, the raw PM2.5 AQI 2021 world pollution data used for the rankings of the world’s least polluted cities are openly available to download. 


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Smart Air is a social enterprise that creates simple, no-nonsense air purifiers and provides free education to protect people’s health from the effects of air pollution. We are proud to be the only certified B-Corp dedicated to fighting air pollution.