NEW DELHI: Squandering the relief due to rain, Delhi recorded a jump in pollution levels and a smoky haze returned on Monday morning after people flouted the ban on firecrackers on Diwali night.
According to IQAir, a Swiss company that specialises in air quality monitoring, Delhi was the most polluted city in the world on Monday, followed by Lahore and Karachi in Pakistan.
Mumbai and Kolkata ranked fifth and sixth among the most polluted cities in the world.
Delhi recorded its best air quality on Diwali day in eight years on Sunday, with its 24-hour average Air Quality Index (AQI) settling at 218 at 4 pm.
However, the bursting of firecrackers till late Sunday night led to a spike in pollution levels amid low temperatures.
The AQI stood at 275 at 7 am on Monday and gradually rose to 358 by 4 pm.
An AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', 401 and 450 'severe' and above 450 'severe plus'.
"It's evident that the spike in pollution levels post Diwali is due to two factors -- firecracker bursting and farm fires -- with fireworks being the predominant reason in this case," an official of the Commission for Air Quality Management (CAQM), a statutory body responsible for formulation of strategies to reduce pollution in Delhi-NCR, told PTI.
In the 24 hours ending at 4 pm on Monday, the AQI rose from 186 to 349 in Ghaziabad, from 193 to 349 in Gurugram, from 189 to 363 in Noida, from 165 to 342 in Greater Noida, and from 172 to 370 in Faridabad with intense firecracker bursting being reported in these places.
Within Delhi, pollution levels reached the 'severe' category in some areas, including RK Puram (402), Jahangirpuri (419), Bawana (407) and Mundka (403).
The concentration of PM2.5, fine particulate matter that can penetrate deep into the respiratory system and trigger respiratory problems, exceeded the safe limit of 60 micrograms per cubic metre by six to seven times in these areas.
Firecracker bursting pushed the PM2.5 concentration at many places, including Okhla and Jahangirpuri, in the capital over 1,000 micrograms per cubic metre in the early morning hours.
According to Central Pollution Control Board (CPCB) data, cities across India saw a rapid rise in air pollution levels the day after Diwali.
The AQI jumped from 235 to 385 in Uttar Pradesh's Baghpat, from 152 to 361 in Haryana's Kaithal, from 180 to 380 in Punjab's Bathinda, from 211 to 346 in Rajasthan's Bharatpur, from 260 to 380 and from 214 to 355 in Odisha's Bhubaneswar and Cuttack respectively.
According to Delhi Pollution Control Committee (DPCC) data, PM2.5 pollution levels at Jawaharlal Nehru Stadium soared to 1,423 micrograms per cubic metre by 2 am before gradually coming down to 101 micrograms per cubic metre by 12 noon due to a rise in temperature.
The PM2.5 concentration at Okhla stood at 1,629 micrograms per cubic metre at 1 am and dipped to 157 micrograms per cubic metre by 12 noon.
At midnight, the air quality monitoring station at Anand Vihar recorded a PM2.5 concentration of 1,985 micrograms per cubic metre, the data showed.
The concentration of fine, lung-damaging particulate matter PM2.5 and PM10 increased by 45 per cent and 33 per cent respectively on Diwali compared to last year, according to an analysis by the DPCC.
The pollution control body also said nearly all air quality monitoring stations in Delhi recorded an increase in pollution levels on Diwali day compared to the previous year.
Delhi recorded an AQI of 312 on Diwali last year, 382 in 2021, 414 in 2020, 337 in 2019, 281 in 2018, 319 in 2017 and 431 in 2016, according to CPCB data.
The city's AQI a day after Diwali stood at 360 in 2015, 445 in 2016, 403 in 2017, 390 in 2018, 368 in 2019, 435 in 2020, 462 in 2021 and 303 in 2022.
The CAQM official quoted above said stringent measures, including a ban on construction work and the entry of polluting trucks in the national capital, under the final stage of the central government's air pollution control plan called the Graded Response Action Plan (GRAP) will continue until further orders.
"Stubble burning incidents are rising again and the meteorological conditions are not favourable (for dispersion of pollutants).
We will review the situation and act accordingly," the official added.
Delhiites witnessed clear skies and abundant sunshine on Saturday and Sunday as air quality improved sharply just ahead of Diwali this year.
The improvement was attributed to intermittent rainfall on Friday and wind speeds favourable for the dispersion of pollutants.
The city experienced 'very poor' to 'severe' air quality for two weeks starting October 28 with a suffocating haze lingering over the national capital during the period.
In accordance with the practice of the past three years, Delhi has announced a comprehensive ban on the manufacture, storage, sale and use of firecrackers within the city.
Last year, a decrease in stubble-burning incidents, delayed spells of rain, favourable meteorological conditions and an early Diwali prevented the national capital from turning into a gas chamber following the festival of lights.
The Decision Support System, a numerical model-based framework capable of identifying the sources of particulate matter pollution in Delhi, estimated that stubble burning in the neighbouring states, particularly Punjab and Haryana, accounted for 35 per cent of the PM2.5 pollution in the city on Sunday.
It is likely to be 22 per cent on Monday and 14 per cent on Tuesday.
The data also showed that transport -- another major cause of pollution in the city -- contributed 12 to 14 per cent to Delhi's foul air over the past few days.