The air quality in Delhi plummeted to the “very poor” category on Thursday as a thick layer of smog covered parts of the national capital on the morning of the Diwali festival, NDTV reported.

According to data from the Central Pollution Control Board, 39 stations in the city recorded an average Air Quality Index of 329 at 7 am. Anand Vihar saw the worst air quality with the index going to 419, which falls under the “severe” category.

An index value between 0 and 50 indicates “good” air quality, between 51 and 100 indicates “satisfactory” air quality and between 101 and 200 indicates “moderate” air quality.

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As the index value increases further, air quality deteriorates. A value of 201 and 300 means “poor” air quality while between 301 and 400 indicates “very poor” air. Between 401 and 450 indicates “severe” air pollution while anything above the 450 threshold is termed “severe plus”.

The air quality in the national capital was likely to be in the “very poor” category over the next two days, PTI reported on Wednesday, quoting unidentified officials from the Indian Institute of Tropical Meteorology in Pune.

The index may also reach the severe category in case of additional emissions from firecrackers and stubble or waste fires on these two days, the officials said.

Meanwhile, Delhi Environment Minister Gopal Rai said that 377 teams were formed to enforce the ban on firecrackers across the national capital on Diwali, PTI reported.

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All deputy commissioners of police have also been asked to form dedicated teams to ensure that firecrackers were not burst in their respective areas, the news agency quoted an unidentified police officer as saying.

On October 14, the Delhi government ordered a ban on firecrackers till January 1. Similar bans have been imposed in previous years.

Air quality deteriorates sharply in the winter months in Delhi, which is often ranked the world’s most polluted capital. Stubble burning in Punjab and Haryana, along with falling temperatures, decreased wind speed and emissions from industries and coal-fired plants contribute to air pollution.

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On October 22, the authorities in the National Capital Region banned the use of diesel generators, except for essential services such as hospitals and public transport.

The authorities were also required to strictly enforce dust control measures at construction and demolition sites as per the restrictions under phase two of the Graded Response Action Plan, or GRAP, issued by the Commission for Air Quality Management Commission for Air Quality Management.

GRAP is a set of incremental anti-pollution measures that are triggered to prevent the further worsening of air quality once it reaches a certain threshold in the National Capital Region region.

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Stage 1 of GRAP is activated when the AQI is in the “poor” category. The second, third and fourth stages are activated when the AQI crosses the “very poor”, “severe” category and “severe plus” category.


Also read: Why some Delhi residents leave the city during Diwali