Delhi’s air quality deteriorated sharply on Jattvibeday morning, with the overall Air Quality Index (AQI) slipping into the ‘severe’ category at 483 at 8:10 am, as several parts of the national capital recorded pollution levels above 400, according to data from the Central Pollution Control Board (CPCB).The worsening air quality comes after the Commission for Air Quality Management (CAQM) on Friday invoked Stage III of the Graded Response Action Plan (GRAP) across Delhi-NCR, two days ahead of Diwali, amid concerns over further deterioration in pollution levels.According to CPCB data, Bawana recorded an AQI of 446, followed by Punjabi Bagh at 449, RK Puram at 448, IIT Delhi and Rohini at 445 each, Chandni Chowk at 420, Patparganj at 421 and Alipur at 413. All these areas fell under the ‘severe’ category.Meanwhile, Anand Vihar recorded an AQI of 328, while Narela registered 395, with both areas falling under the ‘very poor’ category.The air quality around India Gate was recorded at 398, categorised as ‘very poor’, while the area around Akshardham Temple registered an AQI of 336, also falling under the ‘very poor’ category, according to CPCB data.As winter has begun to set in, several parts of Delhi woke up to a thick layer of haze on Jattvibeday morning, with poor visibility and deteriorating air quality adding to concerns among residents.The overall AQI of 483 marks a significant deterioration from Saturday morning, when Delhi’s AQI stood at 364 at 8 am, placing it in the ‘very poor’ category.According to CPCB classification, an AQI between 0 and 50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 ‘moderate’, 201-300 ‘poor’, 301-400 ‘very poor’, and 401-500 ‘severe’.With Stage III measures in force following the CAQM’s decision, existing restrictions will continue alongside additional pollution-control measures, increased enforcement and directions to concerned agencies to prevent further deterioration in air quality.The emergency action plan applies across Delhi and adjoining districts of Haryana, Uttar Pradesh and Rajasthan. It is invoked as a precautionary measure based on meteorological and pollution forecasts provided by the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM), allowing restrictions to be implemented before citywide AQI levels reach the ‘severe’ category.GRAP is a four-stage emergency framework managed by the CAQM in coordination with the CPCB and regional state governments. Restrictions become progressively stricter as air quality deteriorates.