Mumbai leaves Delhi behind, ranks as world's second-most polluted city

Mumbai has overtaken Delhi to become the world’s second-most polluted city in terms of the global Air Quality Index (AQI). According to Switzerland-based air quality monitoring tech company IqAir, Sarajevo in Bosnia has been ranked as the world's most polluted city for the period between January 29 and February 8.   

As per the AQI data on the IqAir website, Mumbai has an AQI of 163, which falls under the unhealthy category.  

Lahore is in the third position. Delhi is in the sixth spot with 155 US AQI, while Kolkata is in the 17th position with a US AQI of 135. 

As per past records of IqAir, Mumbai at the 10th position on the most polluted list on January 29. It rose to the top on February 2, following which the air quality improved marginally around February 8.  

But on February 13, it surpassed Delhi to become the second most polluted city in the world for air quality. IQAir has joined hands with United Nations Environment Programme (UNEP) and Greenpeace to measure the air quality in India. Its studies are based on data from the Central Pollution Control Board (CPCB).  

Why Mumbai’s air quality is falling 

During the peak winter months of November to January in 2022-23, air quality in India’s financial hub, Mumbai, has noticeably fallen due to various factors. Experts have blamed the dust due to roads and construction activities and smoke from vehicles for the high pollution levels in Mumbai. A 2020 study by NEERI and IIT-B has stated that road or construction dust is the main source of air pollution in Mumbai as there is a heavy concentration (about 71 per cent) of the particulate matter in Mumbai's air. The remaining comes from industrial and power units, airports, and garbage dumps. 

The above factors combined with lowered wind speed across the west coast due to the La Nina effect have immensely contributed to the deteriorating air quality. 

Delhi vs Mumbai air quality 

Air quality falls mainly due to emissions and particulate matter. The weather or climate cannot generate emissions. Cities like Delhi are in a disadvantageous position as it is landlocked for all sides.    

In comparison, Mumbai is a coastal city and naturally has the advantage of natural cleansing. Stronger surface winds blow away air pollutants from the land and bring in the fresh air.  

But scientists have noticed that in recent times that even in coastal areas, the air quality is suffering due to climate change patterns. The temperatures are high and there are more incidences of extreme weather.  

The La Nina phenomenon in Mumbai this year delayed cleaner sea wind reversal in the city and surrounding areas. This affected the natural cleansing mechanism of the city and there was more concentration of particulate matter due to high-flying dust emissions. Besides, the import of transboundary pollution from more polluted regions due to wind pattern changes has added to Mumbai’s falling air quality.