The choke is on Delhi: Pollution turns severe

that only green firecrackers, which cause 30% less pollution, be sold. But a large number of illegal crackers could be heard going off across the region, almost nonstop from about 8pm till late into the night.

Experts said that the post-diwali air on Monday was the cleanest in four years but the pollution remained in the “very poor” category, with the PM2.5 level rising to 18 times the safe limit.

According to scientists at pollution forecasting agencies, the air is likely to worsen over the coming days since a north-westerly wind is bringing with it smoke from Punjab and Haryana, where crop stubble burning is at its peak this week.

Satellites picked up at least 2,200 instances of fires in Punjab and Haryana on Monday, most of them cases of stubble burning. On Tuesday, the India Meteorological Department (IMD) said the figure stood at 1,602 just for Punjab, the most recorded on a single day this season. Experts have previously predicted that more crop residues are burnt around the time of Diwali since farmers can show them as incidental fires. They use the method to quickly and cheaply ready their fields for the next round of sowing.

IMD scientists said “smoke” reduced visibility in the national capital and in its neighbouring cities on Tuesday. The wind speed was low at about 7-8 kmph, not enough to disperse the pollution left behind by Diwali celebrations.

“The pollution from Diwali is still accumulated near the ground. Wind direction is westerly and north-westerly. The high pollution level in Delhi is because of the smoke from stubble burning,” said Kuldeep Shrivastava, director, Regional Weather Forecasting Centre.

VK Soni, a senior scientist at IMD, said: “What you are seeing outside is smoke; because there is no moisture in the air, there is no chance of mist. The wind direction is also westerly so it seems like smoke from stubble burning is impacting air quality.”

Soni added that wind speeds are likely to pick up slightly once clouds caused by cyclonic system Kyarr clear up over the next couple of days.

But that will result in only a marginal improvement. “In all the Indo-gangetic plain cities, low wind speed has caused an accumulation of pollution.”

Delhi chief minister Arvind Kejriwal appealed “with folded hands” to Punjab and Haryana to take steps against stubble burning to prevent the national capital from becoming a “gas chamber”. “At our level, we are making all possible efforts and will continue to do so,” he tweeted.

The Aam Aadmi Party (AAP) government later said in a statement that latest Nasa images showed a drastic spurt in crop residue burning in the neighbouring states.

“The effective stubble fire counts of Haryana and Punjab have increased from 1,654 to 2,577 during the past 24 hours, which is a matter of extreme concern for the residents of Delhi,” it said.

Farm fires and emissions from firecrackers result in heavy concentrations of PM2.5 ultrafine particles in the air, which can lead to major health problems since they can enter the bloodstream after penetrating deep into the lungs.