25 Most Polluted Cities in the World (2021 Rankings)

Air pollution is one of the leading causes of death around the world. But which cities and countries are the most polluted in the world? Smart Air analyzed 2021 air pollution data for 540 major cities from 182 countries around the world to produce the 2021 ranking of the “25 Most Polluted Cities in the World”.

Watch: Run Down of Top 5 Most Polluted Cities in the World
Top 5 Most Polluted Cities in the World (2020 Rankings)

Scroll down below for the full rundown of the world’s most polluted cities, which countries they’re in, and their annual PM2.5 levels:

Rankings: 25 Most Polluted Cities in the World in 2021

1. Lahore, Pakistan (106 µg/m3)

Lahore air pollution ranked worst in the world in 2021

2. Ghaziabad, India (90 µg/m3)

Ghaziabad air pollution ranked 2nd worst in the world in 2021

3. Delhi, India (87 µg/m3)

Old Delhi air pollution ranked 3rd worst in the world in 2021

4. Aguascalientes, Mexico (86 µg/m3)

Aguascalientes air pollution ranked 4th worst in the world in 2021

5. New Delhi, India (79 µg/m3)

New Delhi air pollution ranked 5th worst in the world in 2021

6. Lucknow, India (66 µg/m3)

Lucknow air pollution ranked 6th worst in the world in 2021

7. Muzaffarnagar, India (60 µg/m3)

Muzaffarnaga air pollution ranked 7th worst in the world in 2021

8. Dhaka, Bangladesh (55 µg/m3)

Dhaka air pollution ranked 8th worst in the world in 2021

9. Peshawar, Pakistan (55 µg/m3)

Peshawar air pollution ranked 9th worst in the world in 2021

10. Hapur, India (51 µg/m3)

Hapur air pollution ranked 10th worst in the world in 2021

11. Patna, India (48 µg/m3)

Patna air pollution ranked 11th worst in the world in 2021

12. Kampala, Uganda (47 µg/m3)

Kampala air pollution ranked 12th worst in the world in 2021

13. Kabul, Afghanistan (45 µg/m3)

Kabul air pollution ranked 13th worst in the world in 2021

14. Chandigarh, India (45 µg/m3)

Chandigarh air pollution ranked 14th worst in the world in 2021

15. Jaipur, India (44 µg/m3)

Jaipur air pollution ranked 15th worst in the world in 2021

16. Gandhinagar, India (43 µg/m3)

Gandhinagar air pollution ranked 16th worst in the world in 2021

17. Bamako, Mali (43 µg/m3)

Bamako air pollution ranked 17th worst in the world in 2021

18. Dushanbe, Tajikistan (43 µg/m3)

Dushanbe air pollution ranked 18th worst in the world in 2021

19. Baghdad, Iraq (42 µg/m3)

Baghdad air pollution ranked 19th worst in the world in 2021

20. Kolkata, India (41 µg/m3)

Kolkata air pollution ranked 20th worst in the world in 2021

21. Manama, Bahrain (41 µg/m3)

Manama air pollution ranked 21st worst in the world in 2021

22. Karachi, Pakistan (41 µg/m3)

Karachi air pollution ranked 22nd worst in the world in 2021

23. Dammam, Saudi Arabia (41 µg/m3)

Dammam air pollution ranked 23rd worst in the world in 2021

24. Hawalli, Kuwait (39 µg/m3)

Hawalli air pollution ranked 24th worst in the world in 2021

25. Visakhapatnam, India (39 µg/m3)

Visakhapatnam air pollution ranked 25th worst in the world in 2021

Read More: The 25 Least Polluted Cities of 2021?


Of the 25 most polluted cities in the world, 12 were located in India, while 3 were located in Pakistan. However, for the most polluted city in the world, Pakistan topped the list.

In comparison to the previous year, China showed improvements in its air quality ranking while India had worsened. In 2020, out of 25 cities with the worst air, 9 cities were located in China and 7 in India. In 2021, China managed to completely stay off the chart while the number of Indian cities increased by 5.

Has China’s air quality really improved? Although China’s major cities saw an overall reduction in PM2.5 by 2.5%, data shows that 6 out of 10 cities analysed saw an increase in PM2.5 and 9 out of 10 saw an increase in PM10.

Read More: Has Pollution in China’s Major Cities Increased in 2021?

All of the ranked cities had average air quality many times above the WHO recommended healthy limit. Many of the cities with the worst air quality are located in similar geographical areas on the globe. Other countries featured on the list include Kuwait, Saudia Arabia, Bahrain, Iraq, Tajikistan, Afghanistan, Bangladesh, Mexico, Mali, and Uganda.

Data bias

Some readers may note that only two cities in Africa – Kampala in Uganda, and Bamako in Mali – made the list. No cities or countries in South America were on the list. This does not mean that these cities aren’t polluted. Africa and South America lack air pollution reporting tools, so it is difficult to know the pollution levels on-the-ground in many of these cities.

The fact that so many Indian cities featured in the list is testament to the fact that they have large and wide air pollution monitoring networks set up to detect pollution levels.

Air Pollution Heat Map Paints a Clearer Picture

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 Most 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 most 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 most polluted cities are openly available to download.

How I Protect Myself

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