Air Quality Index (AQI) is a measure of air quality computed by taking into account major air pollutants such as particulate matter, carbon monoxide, sulphur dioxide, and nitrogen dioxide. AQI is largely measured for PM2.5 (particulate matter), which can enter deep into the lungs and cause health ailments.
Delhi’s fears came true in spite of the Supreme Court’s order that only green firecrackers, which cause 30 per cent less pollution, can be retailed, and the Arvind Kejriwal government’s mega laser show to dissuade people from bursting crackers.
According to the Ministry of Earth Sciences’ air quality monitor, the System of Air Quality and Weather Forecasting and Research (SAFAR), levels of PM2.5 tiny particulate matter of diameter 2.5 or less than 2.5 microns that can enter deep into the lungs reached as high as 735 at Delhi University.
Delhi’s overall air quality index (AQI) stood at 463 at 11.30 am, according to SAFAR. The AQI at Pusa, Lodhi Road, Airport Terminal T3, Noida, Mathura Road, Ayanagar, IIT Delhi, Dhirpur, and Chandni Chowk was 480, 436, 460, 668, 413, 477, 483, 553 and 466, respectively. However, according to Central Pollution Control Board (CPCB) data, Delhi’s overall AQI stood at 348 at 11.30 am on Monday. It was 337 at 4 pm on Sunday.
The city on Sunday recorded its cleanest Diwali air in five years, since air quality monitoring began in Mumbai. However, researchers have predicted a marginal spike in pollution levels on Monday.
AQI on Sunday for PM2.5 was 30 (good) during the day, which increased to 87, that is considered satisfactory by evening. An AQI of 118 (moderate) has been predicted for Monday, 70 (satisfactory) for Tuesday, and 76 (satisfactory) for Wednesday, according to the System of Air Quality Weather Forecasting and Research (SAFAR).
“Cyclone Kyarr has managed to keep air pollution levels to its lowest for the west coast, and of the four cities where SAFAR records air quality, Pune followed by Mumbai were the cleanest, while ‘moderate’ pollution was witnessed in Ahmedabad, and ‘very poor’ levels in Delhi during Diwali,” said Gufran Beig, project director, SAFAR.
The air quality in the city and the surrounding areas was recorded in the “moderate” category on Kali Puja on Sunday, officials said.
The air quality index or AQI was at 182 at Ballygunge, while it was at 111 in Bidhan Nagar at 11 pm, they said. At Jadavpur monitoring station, the AQI was recorded at 143 and at Rabindra Bharati it was measured at 173.
At Rabindra Sarobar the AQI was measured at 147 and at Victoria Memorial it was 98, which is “satisfactory”. Air quality recorded at ‘moderate’ level causes breathing problem to those having asthma and other respiratory problem.
On last Kali Puja, the index breached the 250-mark. However, better vigilance and more awareness this time helped keep the AQI in the “moderate” level, officials said.
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Earlier this month, the Union minister for health, Harsh Vardhan had announced that green fireworks would resolve the crisis of air pollution, cut down on noise, and will be available at the same retail price. However, these green-crackers are still not easy to find in the city markets.
Unaware of what ‘green’ crackers are, many customers in the city claim that pollution is not a major issue for the city as the air pollution levels here are less than, say, Delhi and Mumbai. While some blamed the lack of availability of ‘green’ crackers for their low sales, shopkeepers blamed it on the lack of demand among customers.
Particulate Matter 2.5 (pollutants smaller than 2.5 microns) was measured at 720 at Sanatnagar on Diwali evening, more than twice the upper limit of 300.
According to data collated by the World Air Quality Index, the PM 2.5 level stood at 472 at Begumpet, near the US Consulate.
Multiple requests for information on pollution levels from the Telangana State Pollution Control Board went unanswered.
Except Sowcarpet in north Chennai, the ambient AQI in the city on Diwali day were within permissible limits in all areas. According to the state pollution control board PM10 stood at 128 against the maximum safe level of 100. In the same area PM2.5 levels at 62 were higher than the safe maximum of 60.
After Dewali last year, PM10 levels were at 114 and PM2.5 was at 42 in Sowcarpet. Noise levels on Diwali day rose to 73 decibels as against the maximum permissible 55 decibels.
In a release, the pollution board has said, “The considerable reduction of pollution level was mainly due to public co-operation in complying with the Supreme Court directions and the awareness created by the TNPCB with co-operation of the other government departments and media.”
According to Sunil Dahiya, analyst (Energy and air pollution) Greenpeace (a non-governmental organisation), PM2.5 concentrations were observed at above 200 micrograms at most of the stations, taking it to the ‘hazardous’ category. “When it was raining in most parts of the city on Sunday evening, around the time crackers are burst most, we thought the air quality would not touch hazardous levels. However, the data recorded shows that we, as citizens, have our ways of contributing to air pollution,” he said.
Many residents were actually glad when it started raining on Sunday evening. D.S. Rajashekhar, former president of the Citizens Action Forum, noted that the number of people bursting crackers had come down this year. “The rain also helped as many were not able to burst firecrackers,” he said.
By Phurpa Lhamo and Sashwata Saha