A thick layer of smog is seen over the city skyline, at Chowpatty, on Sunday. PIC/SHADAB KHAN
Mumbai's air quality has remained in the 'moderate' category -- which poses a risk to those with respiratory illnesses, heart problems, and asthma -- throughout the first week of December, continuing with the moderate AQI (Air Quality Index) streak that began on November 7. The first week of November recorded an AQI in the satisfactory category. Annually, Mumbai records its worst air quality in the winter months of December and January.
However, despite consistently bad air quality, December's average AQI stood around 122 during the first week, which is much lower than the average AQI during the same time in 2024, which was around 148, according to data from the Central Pollution Control Board (CPCB). Last year, AQI peaked at 174 during this time due to ozone -- the secondary pollutant contributing to smog -- and particulate matter, and December 2024's worst reading was 199. This year, AQI has peaked at 138 in December so far, and nitrogen dioxide (NO2) is the worst pollutant -- the primary pollutant contributing to smog -- which can come from construction and industrial emissions, apart from other contributors.