Experts said while the level of sulphur dioxide is still in control in Delhi and national capital region.
The dense cover of grey haze shrouding Delhi for almost a week, reminiscent of the 1952 Great Smog in London, plunged the city's air quality on Sunday to the season's worst.
The real-time readings of respirable pollutants PM 2.5 and PM 10 breached the safe standards by over 15 times at many places this morning. The hourly AQI (air quality index) of monitoring stations run by CPCB and SAFAR remained 500 plus, which is beyond the maximum limit.
Experts said while the level of sulphur dioxide (SO2) is still in control in the city, in terms of other parameters like volume of particulates, the situation was nearly as bad as the infamous London episode that had resulted in around 4,000 premature deaths.
"In London smog of 1952 about 4,000 people had died prematurely when average PM levels were about 500 microgramme per cubic metre along with high SO2 levels. Here, (the concentration of) SO2 may not be that high, but as we saw on Diwali, several gases had increased substantially. Overall it is a toxic cocktail.
Metro running amid heavy smog in Gurgaon on Sunday. (PTI Photo)
"Persisting high levels can lead to more premature deaths in Delhi also," Anumitra Roychowdhury of Centre for Science and Environment (CSE) told PTI.
In view of the intense air pollution, Delhi Chief Minister Arvind Kejriwal on Sunday announced number of measures to check dipping air quality.
All constructions and demolitions have been banned for five days, water will be sprinkled on roads and strict action will be taken against the burning of trash, Mr Kejriwal said after an emergency cabinet meeting on Sunday.
The odd-even road rationing scheme may return, the chief minister said. All schools will remain closed for three days.
Air pollution is responsible for around 10,000 to 30,000 deaths in the national capital every year, the CSE had said in a report last year.
At 4 pm on Sunday, the 24-hour-average AQI of the city was at a staggering 497, three steps down the maximum of 500, which was the season's worst, even compared to post Diwali pollution levels.
PM 10 is 100.
CSE, which said the prevailing spell of smog in Delhi is the worst in 17 years on, welcomed the emergency measures taken by the Delhi government.