It is certainly not a record to celebrate for New Delhi. The Indian metropolis and capital "wins" for the third consecutive year the title of world's most polluted capital, awarded by the Swiss institute IQAir in its 2020 World Air Quality Report, based on atmospheric concentrations of PM2.5 (particles fine enough to penetrate all the way to the bronchi).

Ranking	City	Country	Average PM2.5 concentration
1	New Delhi	India	84.1
2	Dhaka	Bangladesh	77.1
3	Ulaanbaatar	Mongolia	46.6
4	Kabul	Afghanistan	46.5
5	Doha	Qatar	44.3
6	Bishkek	Kyrgyzstan	43.5
7	Sarajevo	Bosnia-Herzegovina	42.5
8	Manama	Bahrain	39.7
9	Jakarta	Indonesia	39.6
10	Kathmandu	Nepal	39.2

Air quality in New Delhi is disastrous

It is impossible not to notice that, scrolling through the top fifty places in the ranking of the most polluted cities, 49 are located in Bangladesh, China, India and Pakistan. The levels of atmospheric particulate matter recorded in India are staggering. Although all monitored cities saw an improvement compared to 2018, and 63 per cent compared to 2019, 22 of the 30 most polluted cities in the world are Indian.

In the past year, farmers resorted particularly intensively to the practice — formally prohibited — of burning stubble in order to convert plantations more quickly during the transition from one season to another. From the fields of Punjab alone comes between 20 and 40 per cent of the air pollution that chokes New Delhi, the world's most polluted capital. In November, PM2.5 levels reached a daily average of 144 μg per cubic metre, and in December as high as 157; for context, the World Health Organization (WHO) sets an annual average target of 10 μg per cubic metre.

According to a study conducted by IQAir together with Greenpeace Southeast Asia, as many as 54,000 premature deaths recorded in the Indian capital in 2020 can be linked to exposure to PM2.5. Including Mexico City, São Paulo, Shanghai and Tokyo, the total reaches 160,000 people.

The effects of lockdown on fine particulate matter

The 2020 data were significantly affected by the containment measures introduced during the coronavirus pandemic. Compared to the previous year, an improvement in air quality is observed in 65 per cent of the monitored cities. However, since these are entirely exceptional circumstances, the researchers stress, these gains will be short-lived.

Moreover, while motorways and offices emptied, unprecedented fires — also influenced by climate change — blazed across California, Australia, Siberia and South America. Meanwhile, Indonesian and African forests were set alight to make way for agricultural land. The result was very high levels of fine particulate matter that spread across surrounding areas, at least partly cancelling out the effects of the lockdown.