The air quality in parts of Delhi turned “very poor” on Monday morning, showed real-time figures from the Ministry of Earth Sciences’ SAFAR, or System of Air Quality and Weather Forecasting And Research.

The national capital recorded an average air quality index of 313 at 10.45 am, indicating “very poor” conditions that pose a risk of respiratory problems on prolonged exposure.

According to the Central Pollution Control Board, the 24-hour average air quality index of Delhi was 259 on Sunday evening. This was lowest for the day before Diwali in seven years, PTI reported.

However, on the morning of Diwali, pollution levels increased due to a drop in temperature and wind speed as residents burst firecrackers in several parts of the city.

Levels of the most dangerous particles, called PM2.5, was on Monday morning at 137 micrograms per cubic meter.

Particulate matter smaller than 2.5 microns (or about a ten-thousandth of an inch) is particularly dangerous to human health. Such particles are small enough to travel deep into the respiratory system, potentially impairing lung function.

To be considered safe, the National Ambient Air Quality Standards require PM2.5 concentration to be less than 60 micrograms per cubic metre of air in any given 24-hour period.

The air quality may deteriorate to “severe” levels if firecrackers are burst like last year, SAFAR said.

Last week, Delhi Environment Minister Gopal Rai had said that those caught setting off firecrackers this time would be punished with a fine of Rs 200 and jail term of six months.

Those who manufacture and store firecrackers could be fined up to Rs 5,000 and put in jail for up to three years, he warned. The offenders will be booked under the Explosives Act and Section 268 (public nuisance causing injury, obstruction, danger or annoyance to persons) of the Indian Penal Code.

The Aam Aadmi Party government’s ban on firecrackers was challenged by Bharatiya Janata Party leader Manoj Tiwari in Supreme Court. However, the top court on October 20 rejected Tiwari’s plea and said that people should be able to breathe clean air.

On Sunday, Rai said that the AAP government is focused on saving lives, reported PTI. “We are not interested in politics over firecrackers,” he added. “Some people even moved the Supreme Court over the issue. There is no scope of a debate after the apex courts’ decision in the matter.”

More than 400 teams have been formed to implement the ban on firecrackers in the national capital. These comprise 210 teams of the Delhi Police, 165 teams of the Revenue Department and 33 teams of the Delhi Pollution Control Committee.