The Mumbai skyline, forming a backdrop to the ocean, is one of the city’s most iconic sights. But drive down Marine Drive or the Bandra-Worli sea link these days and you’re likely to see the skyscrapers only through a thick brown mist, particularly in the early morning or around sunset.
Mumbai has an annual tryst with smog or haze during the winter months starting November. However, over the past couple of years, the haze seems to have set in as early as October, a phenomenon that could trigger a variety of health problems for the residents.
According to officials of the Indian meteorological department, haze like conditions, though normally associated with winter, have begun to appear in the months immediately after the monsoon. There are a variety of factors for this. “Post the monsoon the winds that blow through the city are hotter and those bring a lot of dust,” said IMD’s deputy director K. S. Hosalikar.
“Another factor could be that during the monsoon season, a lot of dust and other particles hanging in the atmosphere could be washed down to the ground. After the monsoon, as the weather becomes dryer, these particles could become loosened and float up to the air,” he explained.
While the problem has been gradually exacerbated with increasing population and hence more pollutants are being released into the air, the situation is likely to get worse with the onset of winter and a drop in sea breeze.
Sea breeze is stronger in summer because of the large temperature differences between land and ocean water. As the sea breeze drops in the months following November, it means the pollutants hovering in the air cannot be blown away as easily as those are in summer.
According to a senior scientist at the MeT department, winter sees an inversion of normal temperature patterns, which leads to pollutants being trapped in the lower atmosphere. “Inversions trap a layer of cold air under a layer of warm air and the warm layer then acts like a lid, trapping pollutants near the ground,” he said. According to an official from the Maharashtra Pollution Control Board (MPCB), anything above 100 micrograms of suspended particulate matter (SPM) in 1 cubic metre of air is bad for health. SPM levels fluctuate across the city with the recordings from areas like Sion and Chembur being consistently high.
The MPCB regularly puts out air pollution data, classified according to a colour-coded air quality index (AQI), from its station in Bandra. A look at the data over the past few months illustrates the trend of pollution levels rising sharply post monsoon. In September, up to the last days of the month, the AQI stood at a level below 100 - indicating only minor breathing discomfort to sensitive people.
By the start of October, the readings shot up dramatically over the 100 mark - indicating breathing discomfort to people with lung and heart disease, children, and older adults. On certain days towards the end of the month and through November, it came dangerously close to 200, a level that indicates breathing discomfort to all people on prolonged exposure.
Doctors said the increased levels of pollution are most likely to affect children and patients with chronic lung diseases such as asthma. “Along with the sudden chill in winter, the increase in pollutants means over the last few years, the number of patients coming with breathlessness has increased,” said Dr Ramesh Kulkarni, a GP practising in Thane.
