Explained: Why Mumbai’s air quality is so poor

Bandra Reclamation is shrouded in haze on Saturday afternoon. Pic/Ashish Raje

The city's air quality continues to decline, with a dense layer of haze blanketing numerous areas and reducing visibility. Experts warn that as temperatures are likely to drop in the coming days, there may be no immediate improvement in current conditions. Poor visibility in the city has prompted many netizens to post videos and photos of the smog blanket on social media.

on Sunday evening, the Environment Ministry's SAMEER app recorded Mumbai's overall Air Quality Index (AQI) at 180 (classified as ‘moderate'), marking the fourth consecutive day of thick smog. Earlier this week, the AQI briefly climbed to 198, entering the ‘poor' category.

Smog seen at Gorai Beach on Sunday morning. Pic/Nimesh Dave

Five air quality monitoring stations reported ‘poor' AQI levels, while others indicated ‘moderate' readings.

The worst-affected areas included Borivli East (268), Navy Nagar in Colaba (268), Malad West (262), Mazagaon (244), Kandivli West (233), and Deonar (208).

A hazy Saturday at Bandra Reclamation. Pic/Ashish Raje

According to the AQI scale, readings from 0 to 50 are considered good, 51 to 100 satisfactory, 101 to 200 moderate, 201 to 300 poor, 301 to 400 very poor, 401 to 450 severe, and above 450 severe-plus.

The city's deteriorating air quality has drawn scrutiny from the Bombay High Court. On Friday, the average 24-hour AQI in most parts of Mumbai hovered around or exceeded 200, prompting a bench led by Chief Justice D K Upadhyaya and Justice G S Kulkarni to question whether authorities are taking adequate measures to address the alarming pollution levels.

Hazy skyline in Wadala on Saturday. Pic/Shadab Khan

Dr Gufran Beig, chair-professor at the National Institute of Advanced Sciences (NIAS), provided insights into the haze and reduced visibility. "Normally, when Mumbai's humidity is high, particulate matter attaches to moisture droplets and remains close to the ground, worsening air quality. Currently, moisture levels are low, and strong horizontal and vertical winds propel pollutants upward until they encounter an inversion layer that prevents them from rising further.

As a result, the pollution lingers just below this layer, creating the hazy, smoggy conditions observed from below."

Meteorologists have predicted cooler weather starting from Monday. The IMD's Santacruz observatory recorded a minimum temperature of 20.0 degrees Celsius on Sunday, while the Colaba observatory recorded a minimum of 21.5 degrees Celsius.

Independent weather enthusiast Rushikesh Agre, known for his social media handle ‘Mumbai Rains' on X, wrote: "Cold morning ahead for Mumbai...! Monday and Tuesday seem to be cooler mornings in the next week as WNW (west-northwest) winds will impact Mumbai and Konkan. Borivli-Andheri and Thane-Mulund will be the coolest places in Mumbai. Many areas will record low temperatures."

180
Mumbai's overall AQI on Sunday

268
AQI reported at Borivli on Sunday