Delhi's Diwali started with "very poor" air quality which is predicted to take a turn for the worse irrespective of cracker bursting, according to authorities.
At 8 am, the capital's air quality index (AQI) stood at 341, up from 314 at 4 pm on Wednesday. The 24-hour average AQI was 303 on Tuesday and 281 on Monday.
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', and 401 and 500 'severe'. Beyond that, everything is hazardous.
While SAFAR said the air quality may become 'severe' on November 5 and 6 if firecrackers are burnt, an official from the India Meteorological Department said model predictions do not indicate the AQI reaching the 'severe' category "even with higher emissions".
The Ministry of Earth Sciences' air quality forecast agency said 3,271 farm fires accounted for eight per cent of Delhi's PM2.5 pollution on Wednesday.
It is likely to increase to 20 per cent on Thursday (Diwali) and further to 35 to 40 per cent on Friday and Saturday with the wind direction changing to northwest, it said.
Northwesterly winds carry smoke from farm fires in Punjab and Haryana towards the national capital.
Last year, the share of stubble burning in Delhi's pollution had peaked at 42 per cent on November 5. In 2019, crop residue burning accounted for 44 per cent of Delhi's PM2.5 pollution on November 1.
Delhi Environment Minister Gopal Rai had Wednesday urged the Centre to issue an advisory to Punjab, Haryana and Uttar Pradesh to completely stop stubble burning during the Diwali period so that people could breathe easy after the festival.
The contribution of stubble burning in Delhi's PM2.5 concentration was 32 per cent on Diwali day last year as compared to 19 per cent in 2019.
The contribution of farm fires in Delhi's air pollution has remained low this season so far due to the record-breaking rainfall in October and "unfavourable" wind direction for transport of smoke from stubble burning.
SAFAR said "very calm" local Delhi wind conditions with little ventilation is expected for the next three days which will be unfavourable for dispersion of pollutants.
Under a zero firecracker emission scenario, Delhi's PM2.5 concentration is predicted to be in the upper end of the 'very poor' category from November 4 to November 6.
"However, even if we consider 50 per cent of firecracker load of 2019, the AQI is predicted to degrade to the 'severe' category during the period," SAFAR said.
The PM2.5 concentration in the national capital can surpass 500 micrograms per cubic metre on November 5. The safe limit is 60 micrograms per cubic metre.
On October 27, the Delhi government had launched the 'Patakhe Nahi Diye Jalao' campaign to create awareness against the bursting of crackers.
Action is being taken under relevant IPC provisions and the Explosives Act against anyone found burning crackers under the campaign.
On September 28, the Delhi Pollution Control Committee ordered a complete ban on the sale and bursting of firecrackers in the national capital till January 1, 2022.
According to the government, more than 13,000 kg of illegal firecrackers have been seized and 33 people arrested under the anti-cracker campaign.
(With PTI Inputs)