The air quality in Delhi has started deteriorating again after showing marginal improvement on Monday morning. According to the Central Pollution Control Board (CPCB), the overall AQI of Delhi reached 389 at 8 am on Tuesday, November 16, just about to get into the ‘hazardous’ category (400).

Many of the pollution monitoring stations are witnessing an AQI of over 300 on a real-time basis.

AQI between the range of 51 and 100 is considered as ‘satisfactory’, 101-200 is ‘moderate’, 201-300 falls under the category of ‘poor’. While 300-400 is considered as ‘very poor’, levels between 401-500 fall under the ‘hazardous’ category.

The PM 2.5 (particulate matter 2.5) concentration in Delhi at 7am was 220 micrograms per cubic metre while the PM 10 was 365 ug/m3, according to the 24-hour average figures put out by the Central Pollution Control Board. A PM 2.5 concentration of 300ug/m3 is considered severe. The ‘severe’ threshold for PM 10 is 500 ug/m3.

The share of stubble burning in Delhi’s pollution stood at 10 per cent on Monday, the lowest since Diwali (November 4). On average, farm fires have accounted for around 25 per cent of the PM2.5 pollution in Delhi from November 1 to November 15.

According to an analysis by the Delhi Pollution Control Committee (DPCC), people in the national capital breathed the worst air between November 1 and November 15 every year, as unhelpful meteorological conditions trap pollutants from local sources and stubble burning in neighbouring states of Punjab and Haryana.

The Supreme Court on Monday directed the Centre to call an urgent meeting within 24 hours with Punjab, Delhi, and Uttar Pradesh to devise measures to curb pollution and their implementation. The court posted the case for hearing on Wednesday.