New Delhi: Air quality in the national capital has slipped back to ‘very poor’ category on Friday as the dispersion of pollutants slowed down, authorities said. The overall air quality index was recorded at 315 which fall in ‘very poor’ category, according to the Centre-run System of Air Quality and Weather Forecasting (SAFAR).

At least 16 areas recorded ‘very poor’ air quality, 22 areas in Delhi recorded ‘poor’ air quality while seven areas recorded ‘moderate’ air quality, according to data by the Central Pollution Control Board.

On Friday, the PM2.5 (particles in the air with a diameter of fewer than 2.5 micrometres) level was recorded at 139, while the PM10 (particles in the air with a diameter of fewer than 10 micrometres) was recorded at 210 in Delhi.

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’, and 401 and 500 ‘severe’.

Delhi’s air quality has shown significant improvement in the past two days after rain washed away the pollutants. But as the rain subsided, a rise in pollution level was again recorded on Friday, authorities said.

According to the Indian Institute of Tropical Meteorology, fire counts observed in past 24 hours over a northwest region of India were few (less than 100 counts).

“The impact of biomass burning in northwest India is not significant over Delhi,” it said.

Recently, NASA had released images showing rampant stubble burning activity in the two states. On its official website, it had stated that burning of crop residue in Punjab and Haryana has increased significantly over the past 10 days in and near Amritsar, Ambala, Karnal, Sirsa, and Hisar.

The Supreme Court had refused to impose a blanket ban on the bursting of firecrackers and allowed the use of only green firecrackers with reduced emission and decibel levels during all religious festivals.

Last year, the national capital had witnessed a blanket of thick smog after Diwali, bringing air quality standards to an all-time low in the national capital.