Delhi's air quality oscillates between 'poor', 'very poor'

After a brief respite, Delhi's air quality deteriorated to oscillate between 'poor' and 'very poor' categories on Friday due to increased pollutant holding capacity of air and stubble burning in neighbouring states.

The overall air quality index (AQI) was recorded at 339, which comes under 'very poor' category, according to the Centre-run System of Air Quality and Weather Forecasting (SAFAR).

Central Pollution Control Board (CPCB) data showed the overall AQI at a 'poor' 282.

Delhi's air quality showed significant improvement in the past two days after rain washed away the pollutants but the rainfall also led to increased air capacity to hold pollutants, the SAFAR said.

Air pollution level is on the path of reversal. It increased after the impact of rain got over and the AQI is entering the 'very poor' range, it said.

"The pollution level is likely to deteriorate further by Saturday but will remain in 'very poor' category. Although wind speed is better (higher) but holding capacity (of air) is also high due to moisture, which is unfavourable," the SAFAR said in a report.

Fire counts from stubble burning increased in past 24 hours, which may contribute 8-10 per cent to Delhi pollution, the report said.

On Friday, the level of PM2.5 -- particles in the air with a diameter of less than 2.5 micrometres -- was recorded at 140, while the level of PM10 was recorded at 234, CPCB data showed.

Faridabad recorded 'very poor' air quality while Ghaziabad, Gurgaon, Greater Noida and Noida recorded 'poor' air quality.

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'.

According to CPCB data, 11 areas in Delhi recorded 'very poor' air quality and 26 recorded 'poor' air quality.