The air quality in Delhi worsened this morning as people defied a ban on firecrackers during Diwali celebrations on Thursday.

The relentless bursting of firecrackers caused severe noise pollution and blanketed the national capital in dense smoke with residents flouting the restrictions till late at night.

According to the real-time data provided by the System of Air Quality and Weather Forecasting and Research (SAFAR), Delhi’s air quality index (AQI) soared to 359 at 6:30 am, which falls under the “very poor” category. The AQI on the morning of Diwali was at 328.

An AQI between 0 and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 and 300 poor, 301 and 400 very poor, 401 and 450 severe, and above 450 severe-plus.

Levels of fine particulate matter — dangerous microparticles known as PM2.5 pollutants that enter the bloodstream through the lungs — increased to more than 23 times the World Health Organization recommended daily maximum.

Monitoring firm IQAir said the pollutant levels topped 345 micrograms per cubic metre and rated Delhi as the worst in the world.

The AQI level in most of the 40 monitoring stations in the city remained in the “very poor” category with Anand Vihar and RK Puram reporting the worst air quality index of 395.

Burari Crossing (394), Sonia Vihar (392), Punjabi Bagh (391), North Campus (390), Bawana (388), Jahangirpuri (387), Rohini (385), Ashok Vihar (384), and Nehru Nagar (381) were some other places with the “very poor” air quality.

The Indian Institute of Tropical Meteorology (IITM), Pune, has said that the air quality in the national capital is likely to be in the “very poor” category (AQI 300 to 400) on Friday.

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On Diwali eve, Delhi Environment Minister Gopal Rai announced that 377 teams were formed to enforce the ban on firecrackers across the capital. A senior Delhi Police officer said all deputy commissioners of police (DCPs) were asked to form dedicated teams to ensure that firecrackers do not burst in their respective districts.

Last year, the “festival of lights” was celebrated on November 12 and Delhi recorded its best air quality on Diwali day in eight years, with the average AQI at 218.

Stubble burning or farm fires in neighbouring Haryana and Punjab, especially during the post-harvest season of October and November, are also often blamed for the rise in pollution levels in Delhi.

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The capital has been breathing hazardous air quality for the past few weeks, prompting authorities to impose stage two of the GRAP or the Graded Response Action Plan last week.