Pollution levels in the national capital shot up on Sunday and are expected to enter the "severe" category tonight due to firecracker emissions, unfavourable weather and a significant spike in stubble burning, according to government agencies.
A thin layer of toxic haze hung over Delhi in the morning and the overall air quality index stood at 313 at 9 am. It continued its upward trend and was recorded at 341 at 2.30 pm.
On Saturday, Delhi's overall air quality (302) was in the lower end of the "very poor" category.
The levels of PM10 tiny particulate matter of diameter 10 or less than 10 microns that can enter deep into the lungs reached as high as 515 micrograms per cubic metre in Anand Vihar, according to the Delhi government's air quality monitors.
In Wazirpur and Bawana, PM 2.5 levels crossed the 400 mark.
Twenty-nine of the 37 air quality monitoring stations in the capital recorded their AQI in "very poor" category or beyond.
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The AQI in the satellite towns of Faridabad, Ghaziabad, Greater Noida and Noida was 318, 397, 315 and 357, respectively.
After last year's Diwali, Delhi's AQI had crossed the 600-mark, which is 12 times the safe limit. In 2017, the AQI post-Diwali was 367.
An AQI between 0-50 is considered "good", 51-100 "satisfactory", 101-200 "moderate", 201-300 "poor", 301-400 "very poor", and 401-500 "severe". Above 500 is "severe-plus emergency" category.
The period between October 15 and November 15 is considered critical for Delhi-NCR's air quality due to stubble burning in neighbouring states, firecracker emissions on Diwali and weather patterns across the region trapping pollutants in the atmosphere.
The weather department said, primarily, the westerly winds, which carry smoke from stubble burning in Haryana and Punjab to Delhi-NCR, were blowing in the region.
With Delhi's air quality plummeting to dangerous levels around Diwali every year, the Supreme Court in 2018 banned polluting firecrackers and ordered that only green firecrackers, which is said to cause 30 per cent less pollution, can be manufactured and sold.
But the green pyrotechnics have failed to draw good response both from sellers and buyers, primarily due to lack of variety, limited stock and high prices.
Last year also, people continued to buy the conventional firecrackers and use them.
According to the System of Air Quality and Weather Forecasting and Research (SAFAR), the highest impact of firecracker emissions is expected early on Monday from 1-6 am.
"If 50 per cent of the total load of firecrackers (average of Diwali 2017 and 2018) is added, the AQI may plunge to the severe category for a short period," it said, adding the situation would be not as bad as last year.
SAFAR said stubble-burning incidents in Haryana and Punjab are increasing gradually and following almost the same pattern as last October.
The share of stubble burning in Haryana and Punjab in Delhi's PM2.5 concentration could increase to 19 percent on Sunday, it said.
On Saturday, the Delhi government launched a four-day mega laser show in an effort to discourage residents from bursting firecrackers and celebrating Diwali amid lights and music. During the show, laser lights were beamed in sync with patriotic songs and Ramayana narration.
The prevailing air pollution in the national capital region has also become a cause for concern ahead of the T20 International between India and Bangladesh at the Feroz Shah Kotla on November 3.
Back in December 2017, the Sri Lankan cricket team was left gasping for breath during a Test match at the Kotla, forcing most of their players to wear protective masks even as some fell ill.
BCCI and DDCA officials are now hoping that the city's poor air quality doesn't become an issue during the night encounter.
Apprehending a dip in air quality, the Supreme Court-mandated Environment Pollution (Prevention and Control) Authority on Friday banned construction activities at night in Delhi-NCR from Saturday to Wednesday.
It also directed closure of coal-based industries, barring power plants, in Faridabad, Gurgaon, Ghaziabad, Noida, Greater Noida, Sonepat and Bahadurgarh during the period.
On EPCA's direction, the Delhi Pollution Control Committee (DPCC) have also ordered the closure of industries, which have not yet shifted to piped natural gas, from Saturday-Wednesday.
A PMO-led panel has directed implementing agencies and the NCR states to intensify anti-pollution measures up to mid-November so that there is immediate impact on air quality.
The Centre has also asked Haryana and Punjab to stop stubble burning completely for the next "critical" days.