Delhi's air quality reached the 'severe plus' category on Friday with an AQI above 450. However, the Commission for Air Quality Management decided not to implement stage IV measures of the Graded Response Action Plan due to a declining trend in pollution levels. The average AQI was 468 at 4pm, improving to 456 at 5pm. The sub-committee noted that GRAP stage III had been implemented recently and expected positive results. The primary contributors to Delhi's pollution, such as stubble burning and solid fuels, are not controlled by GRAP.