Among world's 10 most polluted cities, 3 are from India. Check full list here

While Delhi tops the list with an average AQI of 556 as listed by the IQAir service, Kolkata ranks fourth and Mumbai sixth in the entire list. The cities with the worst AQI indices also include Lahore, in Pakistan, and Chengdu, in China.

Mounting levels of air pollution in Delhi, exacerbated by a hazardous amalgamation of smoke from farm fires in the nearby states and the city's local pollution sources such as vehicle emissions, have triggered concerns of a health emergency. Meanwhile, the air quality and pollution city tracking service from IQAir, a Switzerland-based climate group that is also a technology partner of the United Nations Environmental Program, has shown that there are as many as three cities from India on the list of ten cities with the worst air quality indices.

Vehicles ply amid low visibility due to a thick layer of smog at the Delhi- Gurugram Expressway on Friday. (Yogendra Kumar / ANI)

While Delhi tops the list with an average AQI of 556 as listed by the IQAir service, Kolkata ranks fourth and Mumbai sixth in the entire list. The cities with the worst AQI indices also include Lahore, in Pakistan, and Chengdu, in China.

Here are the ten cities with the worst air quality indicators and pollution rankings, according to IQAir:

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1. Delhi, India (AQI: 556)

2. Lahore, Pakistan (AQI: 354)

3. Sofia, Bulgaria (AQI: 178)

4. Kolkata, India (AQI: 177)

5. Zagreb, Croatia (AQI: 173)

6. Mumbai, India (AQI: 169)

7. Belgrade, Serbia (AQI: 165)

8. Chengdu, China (AQI: 165)

9. Skopje, North Macedonia (AQI: 164)

10. Krakow, Poland (AQI: 160)

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Notably, estimates from the Indian Institute of Tropical Meteorology’s (IITM) decision support system (DSS), which provide a forecast for Delhi’s air quality and identify the components of the pollution, said that on Friday, Delhi also received pollutants from other cities such as Jhajjar, Gurugram, Baghpat, Ghaziabad, and Sonepat.

The DSS analysis showed that on Friday, paddy stubble fires contributed to 15 per cent of Delhi’s PM 2.5 (ultrafine particulate matter with diameter less than 2.5 micrometres), local vehicular emissions had a share of 25 per cent, emissions from households contributed to 7 per cent of the particulate levels and industries in Delhi and its peripheries made up 9-10 per cent of the city’s pollution profile.

SAFAR, the Union ministry of earth sciences’ air quality monitoring station, said the stubble fires accounted for at least 35 per cent of pollutants in the air on Friday.