Mumbai skies still hazy, AQI remains stagnant at 186

MUMBAI: Hazy skies returned to Mumbai for yet another day in the city, gathering yet more complaints of poor visibility and dangers to health. While the overall 24-hour air quality index (AQI) is at 186, at the higher end of ‘moderate’ on the AQI scale, several stations had it much worse. This was a negligible improvement from Saturday, when overall AQI was 188.

Four air quality monitoring stations in the city clocked in their 24-hour AQI in the ‘poor’ category. These were Borivali East, Byculla, Malad West and Siddharth Nagar in Worli.

Far more stations, however, had several periods wherein AQI dipped even worse, to the ‘very poor’ and even ‘severe’ levels.

Sewri, for instance, had the levels of PM10 pollutants (particles of size 10 micrograms per cubic meter and under (µg/m3) rising to the dangerously high ‘severe’ levels at several points in the day; starting in the morning from 7 to 8 am, in the afternoon from 1 to 2pm, and again in the evening from 5pm to 7pm. At other points, however, the station did not record any reading of PM10 levels.

The other station with similar patterns was Malad West. There, while PM2.5 levels were in the ‘poor’ category for most of the day, PM10 sharply rose to the ‘severe’ category between 1pm to 2pm, and then promptly stopped recording values thereafter.

Three other stations – Borivali East, Byculla and Siddharth Nagar in Worli - had their AQI dip to ‘very poor’ levels in parts of the 24 hours.

Gufran Beig, chair-professor at the National Institute of Advance Sciences (NIAS), attributed the AQI and hazy look partly to the influence of dust storms. “There are multiple dust storms emerging from border areas of Afghanistan and Iran towards the Arabian Sea, eventually trying to intrude into coastal regions led by Mumbai,” he said. “Meteosat (meteorological satellites) dust images and our model outputs show some dust intrusion to the Arabian sea from Pakistan and Afghanistan towards Mumbai. But this is not very significant due to the heavy winter air, which tends to resist movement over long distances.”

He added that this contribution to dust over the city is possibly being missed by the AQI monitors in the city due to the dust particles – PM10 – staying higher in the air, as the heavier air delays downward descent. This results in hazy upper air, contributing to the look in the city.

“The usual winter conditions are contributing to the look of haze, although it has reduced as the western disturbance has passed. Wind speeds are lower, leading to the buildup of pollutants in the atmosphere,” said Sushma Nair, scientist at the IMD Mumbai. Speaking of the temperature, which was at maximum of 33.5 degrees Celsius and minimum 19.2 degrees Celsius at Santacruz, she said, “Minimum temperatures will come down in the coming days, and the maximum will rise.”

When asked about the intermittent high readings, an official from the BMC’s environment department which had set up and looks after the station, said, “There are construction sites in close proximity to the station, so it might be the direct effect of dust from there. Or the PM10 sensors may not be giving accurate readings and may need calibration, which is a routine process. We will investigate the reason behind it.”

Malad station is managed by the Indian Institute of Tropical Meteorology (IITM), which did not get back with a cause behind the high readings.

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