MUMBAI: The heavy fog enveloping the city during early mornings is an ominous indicator of Mumbai's deteriorating air quality. Official readings since mid-January evidence that owing to cooler weather and bustle of vehicles and construction, the pollution levels have surpassed the standard limits by two-fold.
According to Mumbai Pollution Control Board logs, pollution levels—particularly nitrogen oxide (NOx) and suspended particulate matter (SPM) —have been exceptionally pernicious the past few days. On January 16, for instance, SPM shot up to as high as 286 micrograms per cubic metre. On January 6, NOx was recorded at 211 micrograms per cubic metre.
"Anything above 100 micrograms of SPM and 80 micrograms of NOx in a cubic metre of air is bad for human health," said an MPCB official. Sounding a disquieting note, he added that in certain parts of the city pollution levels are perennially higher than the standard limits.
"When the weather gets cooler, SPM levels do tend to rise because of inversion," said Dr Rakesh Kumar of the National Environment Engineering Research Institute.
Normally, the air near earth's surface is warmer than that in the upper atmosphere. During inversion, however, there is cold air near the surface, which gets trapped under warmer air.
"At such a time, hot and cold air do not mix easily in the upper atmosphere. Because of this, pollutants get trapped in the lower atmosphere," explained Dr Kumar. "Strong winds break inversion and blow away pollutants."
Experts say a dip in the mercury is not the only cause of Mumbai's poor air quality—increasing vehicular density and construction pollution are equally to blame. "Pollution norms for vehicles may be in place, but their sheer numbers in Mumbai override those and lend to the addition in SPM levels," said Dr Neelam Rane, professor of physiology at D Y Patil Medical College. "Vehicles emit more pollution when moving slow. In Mumbai, the problem gets amplified due to bumper-to-bumper traffic. Also, there is always some construction, renovation or restoration work happening, which is an even greater source of pollution," Dr Rane continued.
Dr Kumar noted that the SPM and NOx readings were made at Bandra and Sion stations. "Both these areas suffer major traffic issues. This is why pollution levels are high in these areas."
The Brihanmumbai Municipal Corporation had written to other government agencies earlier this month, asking them to adopt measures to prevent SPM from getting dispersed in the air. But its initiative is still nascent. Before an action plan is set rolling, the civic body wants to conduct studies to gauge the precise correlation between construction activities and pollution.
