Explainer: Why Mumbai recorded air quality poorer than Delhi's. All you need to know
Several measures have been taken up by the BMC to mitigate the aggravating air quality.
At a four-year high mark for October in particulate matter (PM)-10 as well as temparature, Mumbai is reeling under air pollution levels worse than that of Delhi's. The air quality index (AQI) in several places of the city had breached the 200-mark, which is considered ‘poor’ and causes serious health hazards. The condition is believed to continue for a while at a time when the city braces for the possible onslaught of cyclone Tej which is brewing in the Arabian Sea, that has now intensified into an extremely severe cyclonic storm.

Also read: Delhi vs Mumbai air pollution: Which city fares better? Take a look
Due to several factors, Delhi has been struggling to safeguard its air quality, the aggravating AQI in the financial capital has raised eyebrows. Although, this is not the first time citizens in Mumbai had to breath more polluted air than Delhiites. Between January 1 and February 17, the AQI in Mumbai remained higher than that of Delhi's for 12 days. Whereas, Mumbai's AQI during last winter registered at ‘poor’ and ‘very poor’ for 66 out of 92 days.
However, there had been variations in the data provided by SAFAR and Central Pollution Control Board (CPCB) – both centrally-run platforms – due to the difference in the strength of their monitoring stations.
Note: PM-10 and PM-2.5 are air pollutants made of a mixture of chemical species. Particles with a diameter of 10 microns or less are inhalable and can induce adverse health hazards. Particles with a diameter of 2.5 microns or less are considered fine particulate matter, which is a portion of PM-10.
What are the causes of Mumbai's substandard air quality?
While several reasons are being associated with the current situation of Mumbai's air quality, with the primary cause is believed to be the dust arising from construction sites. Other causes being climate change; road dust and its displacement; usage of unclean fuels in restaurants, dhabas, bakeries and roadside eateries; open burning of solid waste and garbage; and the industries that include those using Ready Mix Concrete (RMC) plants and casting yard plants.
Dust from construction sites:
The Brihanmumbai Municipal Corporation (BMC) earlier warned that it will stop all the government and private construction projects if they fail to meet the dust and pollution control measures. Accordint to municipal commissioner Iqbal Singh Chahal, construction is going on at a whopping 6,000 sites in the city currently.
As the city officials concluded dust from construction sites as the key contributor, Chahal listed out stringent list of dos and don’ts for developers to follow. Key mandates are to enclose all under-construction buildings in an area of one acre or more with 35-feet high iron or cloth sheets and installing sprinklers at all sites within 15 days, and smog gun system within a month.
Climate change:
The dip in La Nina – the cooling of the ocean surface and change in wind patterns – partially caused a sudden spike in the particulate matter in the coastal city. The dip in the periodic cooling of the sea surface leads to a defers the strong wind reversal from across the sea, keeping the pollutants hanging in the lower atmosphere for longer period.
Road dust:
Another cause of pollution in the city is found to be the displacement of dust particles from roads and vehicles carrying construction debris. As a result, the municipaly officials decided to operate anti-smog guns on 50 to 60 major roads.
Chahal instructed that vehicles transporting construction debris shall be covered properly with tarpaulin sheets and not carry more than the prescribed load.
The transport commissioner has also been directed to take stringent action against vehicles which are past their service life, do not have a Pollution Under Control (PUC) certificate or are overloading.
Use of unclean oils for cooking in eateries:
Cooking at several restaurants, dhabas and other eateries using unclean oils can emit ultrafine particles including oil droplets and condensed organic compounds. Unclean kitchens can also produce nitrogen di-oxide, carbon mono-oxide and formaldehyde in harmful concentrations.
In April, the BMC formed task forces to conduct weekly drive to identify those restaurants, bakeries and banquet halls those were using unclean oils as well as fuels to fire the ovens.
Open burning of solid waste and garbage and use of Ready Mix Concrete (RMC) plants and casting yard plants are among other reasons for Mumbai's poorer air quality.

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