Mumbai wakes up to thick layer of haze and low visibility, experts explain why

Several areas, including the Marine Drive precincts, are experiencing low visibility. Data from the Central Pollution Control Board (CPCB) indicated that the worst air quality was recorded in Byculla, with an AQI of 169. This was followed by the area around Mumbai airport at 163, Malad West at 161, and Worli at 157. Of the city’s 22 monitoring stations, only one — Borivali East with  AQI of 93 — reported ‘satisfactory’ air quality.

Scientists from the India Meteorological Department (IMD) Mumbai airport observatory recorded a low visibility of up to 1 km on Wednesday morning. For perspective, the visibility range in Mumbai normally lies in the 2-3 km range.

Despite the low visibility, officials maintained that no flight services were affected as the advisory to airport authorities is typically issued in Mumbai when the visibility plunges below 500 metres. Experts attributed the low visibility and haze to low wind speeds, which entrap pollutants within the atmosphere.

Despite the low visibility, officials maintained that no flight services were affected as the advisory to airport authorities is typically issued in Mumbai when the visibility plunges below 500 metres. (Express Photo)

Speaking to The Indian Express, Sunil Kamble, director of IMD Mumbai, said: “Currently, the speed of winds in Mumbai is zero, and as a result, no wind speed or wind direction is being registered. When there are winds, the suspended particulates in the air get dispersed. However, when the wind speed is low or zero, the particulate matter remains suspended in the air, resulting in haze and poor visibility. The situation improves after a few hours when the wind direction changes and the wind blows in.”

Kamble said this is a typical phenomenon experienced during the winters owing to a combination of meteorological factors such as calm winds and man-made factors. On Wednesday, minimum temperatures touched 20 degrees in Santacruz, which is 3.3 degrees above normal, while the Colaba station logged 21.8 degrees.

Bhagwan Kesbhat, environmentalist and founder of NGO Waatavaran, said: “During the winter months, Mumbai experiences cooler nights, leading to temperature inversions where cooler air is trapped near the ground beneath warmer air. This inversion prevents pollutants from dispersing, causing them to accumulate near the surface. Combined with high humidity from Mumbai’s coastal location, this results in the formation of smog, as moisture binds pollutant particles together.”

Dr Tuhin Banerji, scientist and member of Bombay Environment Action Group (BEAG), said haze is formed when the primary pollutants in the atmosphere are ground-level ozone and volatile organic compounds (VOCs).

“The ground-level ozone and VOCs are primarily caused by solid waste burning, vehicular pollution, and industrial emissions. Because of low wind speeds, all the pollutants from these man-made factors, which are normally flushed out, are getting trapped within the island city. Heavy traffic congestion, construction activity, and unchecked industrial pollution in Mumbai’s nearby areas, where there are no proper monitoring mechanisms by the Maharashtra Pollution Control Board (MPCB), are some key man-made factors adding to the pollution levels,” said Banerji.