Is Delhi the most polluted city on Earth? Not quite

There’s no such thing as fresh air in the Indian capital right now, with toxic smog reaching “unbearable levels” at the weekend. 

The concentration of harmful PM 2.5 particles in the atmosphere hit 810 micrograms per cubic metre (mpcm) on Sunday morning. To provide a little context, the highest reading anywhere in London is currently 65, the recommended World Health Organisation safe daily maximum is 25, and anything above 300 is considered “hazardous”. 

Every winter, the megacity of 20 million people is blanketed by car fumes, industrial emissions and smoke from stubble burning at farms in neighbouring states. PM 2.5 refers to fine particles (2.5 micrometres or smaller in diameter), which are produced by combustion, including motor vehicles, power plants, forest fires, and some industrial processes.

“Pollution has reached unbearable levels,” Arvind Kejriwal, Delhi’s chief minister, tweeted on Sunday.

Visibility was so poor that airlines have been forced to divert flights, while cricket players were seen training in masks ahead of a Twenty20 international between India and Bangladesh. Schools were closed on Monday, construction work halted, and thousands of cars ordered off the roads. 

“It’s actually scary – you can’t see things in front of you,” a protester told an AFP reporter at a rally on Sunday calling for politicians to take action. 

Is Delhi the world's most polluted city right now?

Not quite. According to the real-time Air Quality Index, the PM 2.5 concentration in Delhi today is as high as 181mpcm. It would appear that measures to tackle the smog crisis have had some impact. Higher readings can be found right now in other Indian cities, including Kanpur (263), Lucknow (257) and Kolkata (265). 

Beyond India, several Chinese cities have unhealthy air, including Xian (254). 

Europe’s dirtiest air is currently found in Paveki, Croatia, and Kosjerić, Serbia (both 168). 

But the most hazardous readings are in Africa, with Mityana in Uganda registering 431mpcm, and Secunda in South Africa, home to the largest coal liquefaction plant in the world, a whopping 714. 

Which is the most polluted city on Earth?

While it reached crisis point at the weekend, bad air is nothing new in Delhi. According to the World Health Organisation, it is the 6th most polluted city in the world, with an average (mean) annual PM 2.5 concentration of 143 (based on the period from 2008 to 2017). Ten of the 11 most polluted cities are in India, with Kanpur topping the table.

The world's 20 most polluted cities (PM2.5)

1. Kanpur, India - 173
2. Faridabad, India - 172
3. Gaya, India - 149
4. Varanasi,  India - 146
5. Patna, India - 144
6. Delhi, India - 143
7. Lucknow, India - 138
8. Bamenda, Cameroon - 132
9. Agra, India - 131
10. Gurgaon, India - 120
11. Muzaffarpur, India - 120
12. Peshawar, Pakistan - 111
13. Rawalpindi, Pakistan - 107
14. Jaipur, India - 105
15. Kampala, Uganda - 104
16. Patiala, India - 101
17. Jodhpur, India - 98
18. Narayangonj, Bangladesh - 94
19. Baoding, China - 93
20. Doha, Qatar - 93

Lukavac in Bosnia and Herzegovina is Europe’s most polluted city (and 89th overall) with a mean PM 2.5 reading of 64. In Beijing it is 73, in Mumbai 63, in Shanghai 45, in Johannesburg 41, in Krakow 31, in Paris 16, and in London it is 12. 

Levels of coarser dust particles (PM10), the result of crushing or grinding operations and dust stirred up by vehicles, are actually highest in the Pakistani city of Peshawar – with Delhi in sixth. 

The world's 20 most polluted cities (PM10)

1. Peshawar, Pakistan - 540
2. Rawalpindi, Pakistan - 448
3. Kanpur, India - 319
4. Hamad Town, Bahrain - 318
5. Faridabad, India - 316
6. Delhi, India - 292
7. Karachi, Pakistan - 290
8. Gaya, India - 275
9. Patna, India - 266
10. Varanasi, India - 260
11. Ma’ameer, Bahrain - 257
12. Lucknow, India - 255
13. Riyadh, Saudi Arabia - 251
14. Ras Hayan, Bahrain - 250
15. Nabih Saleh, Bahrain - 244
16. Muzaffarpur, India - 221
17. Islamabad, Pakistan - 217
18. Narayangonj, Bangladesh - 205
19. Lahore, Pakistan - 198
20. Ulaanbaatar, Mongolia - 197

The world's most polluted countries

Pinpointing them is a little more problematic. The WHO tracks air quality at more than 1,600 locations in nearly 100 countries – but all are urban areas. So while Pakistan, Egypt and Mongolia are among the most polluted countries according to 2018 World Air Quality Report, this only refers to pollution in cities. Air quality in the Karakoram mountain range or the Gobi Desert will, of course, be pristine. 

Bangladesh’s urban areas are, on average, the world's most polluted, followed by Pakistan and India. Europe’s most polluted cities are found in Bosnia and Herzegovina, North Macedonia and Kosovo.

The 20 countries with the most polluted urban areas

1. Bangladesh - average PM 2.5 concentration: 97
2. Pakistan - 74
3. India - 73
4. Afghanistan - 62
5. Bahrain - 60
6. Mongolia - 59
7. Kuwait - 56
8. Nepal - 54
9. UAE - 50
10. Nigeria - 45
11. Indonesia - 42
12. China - 41
13. Uganda - 41
14. Bosnia and Herzegovina - 40
15. North Macedonia - 35
16. Uzbekistan - 34
17. Vietnam - 33
18. Sri Lanka - 32
19. Kosovo - 30
20. Kazakhstan - 30

The 20 countries with the least polluted urban areas

Of the 73 countries to feature in the report, Iceland has the least polluted urban areas, followed by Finland and Australia. The UK just misses out on the top 10, coming 13th.

1. Iceland - average PM 2.5 concentration: 5
2. Finland - 6.6
3. Australia - 6.8
4. Estonia - 7.2
5. Sweden - 7.4
6. Norway - 7.6
7. New Zealand - 7.7
8. Canada - 7.9
9. USA - 9.1
10. Portugal - 9.4
11. Ireland - 9.5
12. Spain - 10.3
13. UK - 10.8
14. Malta - 11
15. Luxembourg - 11.2
16. Russia - 11.4
17. Switzerland - 11.6
18. Netherlands - 11.7
19. Japan - 12
20. Germany - 13