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
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)
2. Ghaziabad, India (90 µg/m3)
3. Delhi, India (87 µg/m3)
4. Aguascalientes, Mexico (86 µg/m3)
5. New Delhi, India (79 µg/m3)
6. Lucknow, India (66 µg/m3)
7. Muzaffarnagar, India (60 µg/m3)
8. Dhaka, Bangladesh (55 µg/m3)
9. Peshawar, Pakistan (55 µg/m3)
10. Hapur, India (51 µg/m3)
11. Patna, India (48 µg/m3)
12. Kampala, Uganda (47 µg/m3)
13. Kabul, Afghanistan (45 µg/m3)
14. Chandigarh, India (45 µg/m3)
15. Jaipur, India (44 µg/m3)
16. Gandhinagar, India (43 µg/m3)
17. Bamako, Mali (43 µg/m3)
18. Dushanbe, Tajikistan (43 µg/m3)
19. Baghdad, Iraq (42 µg/m3)
20. Kolkata, India (41 µg/m3)
21. Manama, Bahrain (41 µg/m3)
22. Karachi, Pakistan (41 µg/m3)
23. Dammam, Saudi Arabia (41 µg/m3)
24. Hawalli, Kuwait (39 µg/m3)
25. Visakhapatnam, India (39 µg/m3)
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.
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.
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.
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.
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.
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