Mumbai ranks second most polluted city in IQAir list with AQI of 167

Mumbai has been named the world's second most polluted city in the latest assessment by IQAir, an independent air quality monitoring organisation based in the United States. The city's Air Quality Index (AQI) was recorded at 167, meaning Mumbai has moved well up the list within a week.

The ranking covered 122 cities worldwide. Lahore is at the top with an AQI of 179. Kolkata and Delhi also recorded an AQI of 167, level with Mumbai. PM2.5 was the main pollutant in all three cities.

The ranking comes exactly a week after Mumbai stood fifth on the global list. However, data from government monitoring stations showed a different AQI reading. According to the Central Pollution Control Board (CPCB), Mumbai's AQI on Wednesday, October 21, was 113.

Twenty air quality monitoring stations are operational in the city, and 13 of them reported unhealthy air quality levels. The highest AQI was 161 at Navy Nagar in Colaba. It was 142 at Kherwadi and 140 at Bhandup Complex.

Additional Municipal Commissioner Avinash Dhakne said platforms such as IQAir use hourly averages to track changes in pollution levels. In this method, sudden spikes in pollution show up more sharply in the readings. Some private monitoring systems also use sensors that measure air quality in small areas.

Government agencies, on the other hand, measure ambient air quality at fixed monitoring stations. Platforms combine the readings from government stations with data from other sources. They then average the hourly AQI readings to calculate city-level figures.

For this reason, private platforms and government agencies can report different AQI figures for the same city. Officials have said the readings reflect different measurements, so a direct comparison between the two could be misleading.

Experts have also linked Mumbai's worsening air quality to El Nino. Low wind speeds and warm, humid weather have pulled down the city's air quality, and pollution is trapped close to the ground.