Despite Wednesday being one of the haziest of this season, readings in city’s monitors remain moderate, raising questions about whether authorities are serious about Mumbai’s poor air
The Bandra Worli Sea Link is shrouded in haze on Wednesday. Pic/Anurag Ahire
A thick blanket of haze continued to envelop Mumbai on Wednesday, reducing visibility as the city witnessed high humidity levels and cloud cover, leading to a further increase in overall air pollution. According to the IMD, easterly winds that keep dust particles suspended in the air are to blame for the persistent haze and poor air quality. The average AQI of the city tested 141 (unhealthy for sensitive groups) at 7 pm on Wednesday, while images from across the city indicated ‘hazardous’ levels.
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Meanwhile, the Central Pollution Control Board (CPCB) portal, which compiles AQI readings from the Maharashtra Pollution Control Board (MPCB), Indian Institute of Tropical Meteorology (IITM) and Brihanmumbai Municipal Corporation (BMC) stations, indicated that air quality remained in the moderate category. The highest AQI of 177 was recorded at Byculla, followed by Chhatrapati Shivaji International Airport (T2) at 172, Navy Nagar in Colaba, Vile Parle West and Borivli East (IITM) at 163 and Malad West at 160. The lowest AQI recorded on Wednesday evening, 110, was in Sewri.
Chhatrapati Shivaji Maharaj Terminus surrounded by mist. Pic/Rane Ashish
Concerns persist
According to meteorologists and scientists, haze typically arises from a mix of local weather patterns, suspended particles like dust, and gaseous pollutants from vehicles and other sources, all intensified by high humidity. Though Mumbai’s average Air Quality Index (AQI) has stayed in moderate range, 130 to 180, over the past two weeks, and the BMC boasts of its “progress” in reducing air pollution since December, worries regarding the city’s air quality persist, as haze and low visibility continue to be a frequent sight.
Dr Rakesh Kumar, president of the Society for Indoor Environment (SIE) and former director and head of the NEERI Zonal Centre in Mumbai, told mid-day, “Owing to high moisture in the air and a rise in the humidity level, the city recorded higher pollution levels on Wednesday as the pollutant-carrying capacity increases when there is more humidity. Also, slow wind speed exacerbates the situation. There is a lot of variability in areas in the suburbs and city; if haze and low visibility are reported throughout the city, not only pollution levels but also regional meteorological factors could be at play.”
A view of the city skyline from Bandra Reclamation on Wednesday. Pic/Rane Ashish
Humidity levels were at 88 per cent in south Mumbai and 89 per cent in the suburbs on Wednesday, the same was below 60 per cent on Monday and Tuesday.
According to a scientist from IMD, low temperatures and low wind speeds together result in a drop in natural ventilation. “Also, right now, Mumbai’s air has high moisture content, which causes aerosols to swell and get trapped in the air. This creates haze,” he said.
Bandra Reclamation obscured by smog. Pic/Rane Ashish
Morning woes
Meanwhile, Sunil Kamble, director of the IMD’s Regional Meteorological Centre in Mumbai, emphasised that air quality is worst in the winter season, especially after 10 pm and between 5 am and 7 am. “This is because low temperatures reduce the ability of pollutants to disperse, trapping them. As temperatures increase during the day, pollutants disperse more easily, and the air quality is best between 2 pm and 4 pm. This is why advisories recommend citizens to stay indoors in the morning during winters. This is also why air quality is not an issue during the summer months, even if the extent of pollutants present in the air is the same. Winters in Mumbai are also marked by weaker winds in the reverse direction while tall buildings hinder the mixing of winds, which aid the formation of pockets of high air pollution,” Kamble said.
A layer of haze visible over railway tracks in Borivli. Pic/Nimesh Dave
Explaining the phenomenon, Kamble added: “From night to the following afternoon, easterly winds are present, causing dust particles to remain suspended and create a haze blanket. This happens especially in winter when the temperature cools down; these winds are slow and stagnant so dust particles remain stagnant and a haze blanket is seen. This is a normal phenomenon. When northwesterly winds come, dust particles are dispersed.”
The Coastal Road, near Haji Ali, obscured by haze. Pic/Shadab Khan
Low wind speed
Sunil Dahiya, founder and lead analyst at EnviroCatalysts, attributed the elevated pollution levels and reduced visibility to a mix of high humidity and low wind speed. “Data shows pollution levels aren’t as severe as they were in December, but they’ve been slightly higher between 9 am and 2 pm over the past few days compared to the first week of January. In fact, January 11 recorded a more pronounced spike in pollution. While a visible haze blanket across the city has been causing low visibility on Wednesday, the likely explanation is rising relative humidity (RH). The city’s RH is higher than on other days in January so far, which is one factor leading to lower visibility. Increased humidity combined with low wind speed can give rise to these conditions,” Dahiya explained.
Smog shrouds the viewing deck at Dadar. Pic/Shadab Khan
Influence of disturbances
Elaborating on the situation, Dr Gufran Beig, chair professor at the National Institute of Advanced Sciences (NIAS), said, “Westerly disturbances around northern Pakistan and adjacent regions have led to a cyclonic circulation developing over north and east Rajasthan, the Delhi region, and further south, including parts of Maharashtra and Gujarat. The influence of these disturbances is shifting eastward, reaching the southeast of Uttar Pradesh and northern parts of Madhya Pradesh. As a consequence, a trough has formed extending from east to west. Above the trough, the dense fog is bringing colder conditions, whereas below it—where temperatures are warmer and wind speeds are low—a haze blanket is forming over nearby areas, particularly Maharashtra and Gujarat.”
The Malad skyline veiled in dense smog. Pic/Nimesh Dave
Scientists skeptical
Senior scientists, meanwhile, expressed scepticism about the AQI monitoring stations. “Often, the haze blanket is simply dust or particulate matter trapped in stagnant air. As haze or a dust mass drops to around 10 metres above ground level, the AQI monitors pick it up—unless it stays lower. Still, most AQI stations across the city continue to register moderate readings, which is puzzling,” one scientist remarked.
Health implications
Dr Sanjeev Mehta, a leading pulmonologist at Lilavati Hospital in Bandra, emphasised that AQI figures do not necessarily reflect the health implications.
“Even if monitoring stations report moderate levels, it doesn’t mean people remain unaffected. Thick haze carries pollutants and dust that can be harmful to those with asthma or other respiratory issues. These pollutants also trigger nasal congestion and can affect the lungs. The nose and lungs form one continuous airway, so the entire respiratory system can be impacted. We must remember that the air quality index is only one broad indicator of overall air quality, and there are many crucial factors it doesn’t capture most of the time.”
153
AQI of Siddharth Nagar, Worli, on Wednesday
177
AQI of Byculla at 7 pm on Wednesday
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