Smog and pollution touch toxic highs as weather system prevents dispersal of particulate matter in several cities

This year’s Deepavali was the quietest in recent history, but low-key celebrations across the country didn’t stop the pollution levels from spiking sharply.

In Chennai, which celebrated the festival on Wednesday, pollution levels the following evening inched up to that of Delhi, a city where where smog and pollution touch toxic highs during this season.

Other cities in the south, such as Bengaluru and Hyderabad, also witnessed a sharp rise in air pollution.

The Air Quality Index (AQI), a six-rung classification scale that rates air quality from ‘good’ to ‘severe’, downgraded air quality in Chennai from ‘satisfactory’ on October 16 to ‘poor’ and ‘very poor’ in the days leading up to Deepavali. As of 4 p.m. on Thursday, the AQI for Chennai was 302, just shy of Delhi’s 319.

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The primary pollutant in both cities was PM 2.5, or particles that are smaller than 2.5 microns and linked to respiratory illnesses.

Experts suggest that the weather conditions, which slowed the speed of winds in the Bay of Bengal, resulted in the high levels of pollutants enveloping Chennai.

K. Karthikeyan, former Member Secretary, Tamil Nadu Pollution Control Board, said, “This year, the particulate matter was much higher on Deepavali day than it was last year. It is the duty of the State Pollution Control Board to restrict the emissions in the spread area of Chennai by limiting crackers to maintain the desired air quality.”

In Bengaluru, PM 2.5 was recorded at 13.46 microgrammes per cubic metre on the outskirts to as high as 71.12 in Peenya Industrial estate. The city saw an uptick in cracker smoke on Thursday.

Pollution Check Air quality index in key cities on Deepavali day at 4 p.m., ranging from 'good' to 'severe'. Numbers range from 0-500

Downward trend

“There will be a rise due to bursting of crackers, but we have noticed a downward trend over the past few years. There is a tendency to celebrate a greener Deepavali,” said B. Nagappa, scientific officer, Karnataka State Pollution Control Board.

While last year’s Deepavali saw heavy rain, morning mist and chill had set in this year. Mr. Nagappa expects particulate matter to hover over the city due to lack of dispersal.

Hazy weather is expected in Hyderabad over the next few days, meaning pollution from firecrackers could remain suspended in the air due to temperature inversion, weathermen say.

Meanwhile, pollution data from three real-time continuous air quality monitoring stations in Greater Hyderabad indicated a rise in the levels by 6 p.m. on Thursday, compared to the previous day’s levels.

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Most parts of Mumbai were covered by a thick cloud of smog, mainly due to pre-Deepavali celebrations with the bursting of crackers. There was less noise due to bursting of crackers, but experts say that to beat the noise, many opted for noise-free cracker varieties that added to air pollution.

Delhi traditionally celebrates Deepavali over multiple days, with the bulk of crackers burst before 3 a.m. on Thursday. A Supreme Court ban on cracker sale this year was expected to produce a dip in pollution.

Had it not been for the depression in the Bay, officials said, it would have been the “cleanest Deepavali” in the capital in many years.

“The depression has contributed to poor ventilation or a slowing down of winds this year in Delhi,” said D. Saha, Head, Air Quality, CPCB.

Last year, Delhi had a perfect storm of unfavourable weather that brought in pollution from Haryana and Uttar Pradesh and, an enormous cracker-emission load from within the city that saw the AQI record chart-busting ‘severe’ levels and prompted the authorities to impose a variety of restrictions on traffic movement as well as a Graded Action Plan.

Along with Delhi, the full impact of crackers on air quality and sound levels in Bengaluru, Hyderabad and Mumbai would emerge on Friday.

By 6 p.m. of Thursday, the System of Air Quality Weather Forecasting and Research (SAFAR) rated Mumbai air quality level as ‘poor’ with an Air Quality Index (AQI) of 204. Its forecast said that the air quality will further dip to ‘very poor’ on Friday, with an estimated AQI of 303.

Anti-noise pollution activist Sumaira Abdulali will record the decibel levels in Mumbai on Thursday till midnight.

“The deadline for bursting crackers is till 10 pm. But many people go on bursting till midnight,” she said.

(With inputs from Rohit P.S., Mohit M. Rao, Jyoti Shelar, Deepa Ramakrishnan, Ramya Kannan and Jacob Koshy)