The air quality in Delhi oscillated between “poor” and “very poor” on Wednesday. The overall Air Quality Index was recorded at 281, which falls in the “poor” category, according to the Central Pollution Control Board. Authorities have warned of a spike in the pollution levels after Diwali on Wednesday even if “partially toxic crackers” are burnt compared to last year.

The Centre-run System of Air Quality Forecasting and Research, or SAFAR, recorded the Air Quality Index at 319, which falls in the “very poor” category.

As many as 11 areas in the city recorded “very poor” air quality while 24 areas recorded “poor” quality, PTI reported. Faridabad, Ghaziabad, Gurugram, Noida and Greater Noida recorded “poor” quality air, the pollution control board said.

The AQI on Tuesday morning was recorded at 400, just a point below “severe”. It had then improved to 320 by 6 pm. On Monday, the index had turned “severe” in Delhi, Faridabad, Ghaziabad, Greater Noida, and “very poor” in nearby Gurugram and Hapur.

Winds blowing from the northwest have been carrying biomass-burning pollutants, according to the Indian Institute of Tropical Meteorology. This phenomenon may continue up to Thursday morning. “The increase in PM2.5 concentration is due to change in wind direction, decrease in wind speeds and contribution from biomass burning,” it said. Shallow fog and haze during the daytime is also expected on Thursday.

“Air quality will be bad on Thursday and start to improve from Friday even if partial toxic crackers as compared to 2017 is burned,” SAFAR said. Stubble burning in areas near the national capital is also adding to the pollution, the agency added. It also predicted that the PM10 concentration in Delhi will reach 575 and PM2.5 will be 378 on Thursday if crackers are burst.

Delhi Environment Minister Imran Hussain urged people to help reduce pollution by celebrating a cracker-free Diwali. “I would like to take this occasion to share with the residents of the national capital, the existing ambient air quality position and would like to request the residents to persuade their near and dear ones for desisting from bursting fire crackers and convince their children about the importance of a green and clean Diwali,” he said.

Central Pollution Control Board Member Secretary Prashant Gargava on Tuesday said the board has advised transport authorities to prohibit heavy vehicles from entering the city from November 8 to November 10. An unidentified official of the pollution board said the recommendation was made as such vehicles cause heavy pollution, which could lead to a further decline in air quality.

The pollution authority could also consider inducing artificial rain after Diwali to wash away hazardous pollutants.

Meanwhile, Delhi Transport Minister Kailash Gahlot said the government is prepared to roll out the odd-even road scheme when required, The Times of India reported.

The odd-even vehicle system helps reduce traffic on the roads by prohibiting cars and bikes from plying based on the last digit of their registration numbers – vehicles with odd digits ply on odd dates and the others are allowed on even dates. The scheme was implemented in 2017 in an effort to reduce dense smog that envelopes the city during winter.