MUMBAI: It’s not Delhi, but on Thursday Mumbai came close. A curtain of haze rolled in and hung heavy over many parts of Mumbai, alarming citizens as visibility was poorer than usual. Social media buzzed with comments and images of Mumbai lost in a haze, now a regular feature in winter in this metropolis. On Thursday, however, the haze was particularly dense and murky.
The Brihanmumbai Municipal Corporation (BMC) received an unusually high number of complaints regarding poor air quality. Some citizens were alarmed, many were angry.
The 24-hour Air Quality Index (AQI), taken at 4pm, was 160, in the ‘moderate’ category, but that was no comfort, as visibility had plummeted. Scientists say this is merely an average figure and AQI varies widely across the city.
For instance, Siddharth Nagar in Worli had the worst short spikes. Here, particulate matter of PM10 size reflected an AQI between 401 and 500, characterised as severe, from 7am to 10am. Consequently, AQI here yo-yoed between ‘poor’ and ‘very poor’, breaching permissible levels several times over.
Similarly, Navy Nagar in Colaba too experienced PM10 levels , in the ‘poor’ category on the AQI scale, from 10am till sundown. In Borivali West, PM2.5 levels were over AQI 300 – in the very poor category – from 9am to 8pm. Malad West was similarly plagued with very poor levels of PM2.5. Deonar spiked into the very poor zone with PM 2.5 levels, from 9am to 11am. BKC saw a spike in PM2.5 and PM10 levels, to ‘poor’ levels, between 8am till noon. Kandivali West, Sewri and Mazgaon were in the ‘poor’ category for almost 24 hours.
Worse, air pollution monitors in areas where complaints had poured in, such as Worli, Deonar, Bandra and Shivaji Nagar, were either not working or only partially functional. As a result, AQI in these areas were not taken into account in the city’s overall average AQI.
Weather scientists say haze is essentially a combination of local weather conditions, suspended particulate matter such as dust, and gaseous emissions from vehicles and other sources. A unique combination of these on Thursday resulted in a hazy curtain of low visibility that draped Mumbai.
According to a scientist at the Indian Institute of Technology-Bombay, “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.
Sushma Nair, scientist at the Indian Meteorological Department (IMD), agreed. “A Western Disturbance is approaching Mumbai, bringing in cloudy weather with a lot of moisture from the Arabian Sea and Bay of Bengal. Suspended particles cling to moisture particles, and do not dissipate easily as winter is always marked by low wind speeds,” said Nair. However, she said, the haze should dissipate in the coming days.
As the Western Disturbance passes, the skies will clear up, allowing day time temperatures to rise. However, night time temperatures will drop further, as moisture in the air will decrease, allowing the air to cool, Nair explained, adding that the change will be gradual.
But Mumbai’s rising pollutions levels, a major factor producing haze, are undeniable. Anumita Roy, executive director of the Centre for Science and Environment (CSE), said, “The haze is due to the combination of pollution and atmospheric conditions in winter. Air is trapped and pollution builds up.”
She added, “But the root cause is rising emissions from traffic, construction activity, peripheral industries, burning of waste, etc. If there is no action plan to systematically and drastically reduce this throughout the year, air pollution will have severe health consequences for the population.”
Meanwhile, the BMC tried to tamp down the dust and other particulate matter on the city’s streets, but it made little difference on Thursday. “Around 263km of roads were washed using 188 machines, water tankers, misting machines, mechanical sweepers, litter picker machines and e-sweepers,” said an official. “Around 197 tonnes of construction and demolition debris was also picked up and transported to the debris processing facility.”
