New Delhi is most polluted capital, Byrnihat in Meghalaya tops list of cities

In fact, between 2018 and 2024, New Delhi has topped the list — except in 2022 when N’Djamena edged past it.

PM (Particulate Matter) 2.5, which remains suspended in the air, has significant adverse effects on health, causing and worsening respiratory illnesses as well as leading to an increased risk of cardiovascular diseases.

While the World Health Organization (WHO) annual guideline for PM 2.5 is 5 micrograms per cubic metre (µg/m3), India’s Central Pollution Control Board has set it at 40 µg/m3.

Major sources of PM 2.5 include combustion engines, power generation, industrial activities, crop burning and agricultural practices, and wood and coal burning.

According to the latest report, prepared by Swiss air quality technology company IQAir, 13 of the world’s 20 most polluted cities are in India, with Byrnihat topping the chart with an annual average PM 2.5 concentration of 128.2 µg/m3.

The other cities are Mullanpur (Punjab), Faridabad, Loni, Gurgaon, Ganganagar, Greater Noida, Bhiwadi, Muzaffarnagar, Hanumangarh, Noida, New Delhi (Central Delhi) and Delhi (average for the rest of the city).

India is the fifth most polluted country, with an average PM 2.5 of 50.6 µg/m3 — 10 times higher than the WHO annual PM 2.5 guideline value of 5 µg/m3.

In 2023, India was the third most polluted country.

The report has relied on data from over 40,000 air quality monitoring stations at 8,954 locations in 138 countries, territories and regions. It was analysed by IQAir’s air quality scientists.

Data shows that PM 2.5 concentration levels in Delhi have seen a slight improvement but the NCR region is still heavily polluted.

“India saw a 7% decline in PM 2.5 concentrations in 2024, averaging 50.6 µg/m³ compared to 54.4 µg/m³ in 2023. Yet six of the world’s 10 most polluted cities are in India. The capital, New Delhi, maintained consistently high pollution levels, with an annual average of 91.6 µg/m³, nearly unchanged from 92.7 µg/m³ in 2023,” the report said.

“Air pollution remains a significant health burden in India, reducing life expectancy by an estimated 5.2 years,” it said.

Only seven countries met the WHO guidelines for annual average PM2.5 level. They are Australia, Bahamas, Barbados, Estonia, Grenada, Iceland, and New Zealand. Oceania is the cleanest region, with 57% of the regional cities meeting the WHO guideline value. The region comprises three countries — Australia, French Polynesia and New Zealand.

No city in East Asia, South East Asia and West Asia met the WHO guidelines, the report said.

Other key findings of the report are:

• Only 17% of cities across the world met WHO air pollution guidelines.
• Out of the 138 countries and regions, 126 (91.3%) exceeded the WHO annual PM 2.5 guideline value of 5 µg/m3.
• Central and South Asia were home to the top seven most polluted cities in the world.
• The most polluted major city in the US was Los Angeles.