Delhi's air quality turns severe again, no additional measures for now

Delhi's air quality turned severe again on Thursday due to unfavourable meteorological conditions like low wind speed that prevented dispersion of pollutants, authorities said.

The Central Pollution Control Board (CPCB) data showed the overall air quality index (AQI) in the 'severe' level at 410, while the Centre-run System of Air Quality and Weather Forecasting (SAFAR) recorded an AQI of 372, which falls in the 'very poor' category.

According to CPCB data, 22 areas recorded severe pollution, while 13 areas witnessed 'very poor' air quality.

In the NCR, Ghaziabad and Faridabad recorded 'severe' air quality, while Gurgaon and Noida recorded 'very poor' quality air.

The overall PM2.5 level (fine particulate matter in the air with a diameter of less than 2.5 micrometre) was recorded at 310 and the PM10 level at 475 in Delhi, the CPCB said.

The national capital recorded its second highest pollution level of the year on Sunday with an AQI of 450. The air quality remained 'severe' on Monday and Tuesday. There was slight drop in pollution levels on Wednesday and the air quality had moved to the 'very poor' category.

On Thursday, the air quality again worsened and turned severe.

The CPCB-led taskforce Thursday said no additional steps were suggested in view of the deterioration of Delhi's air quality to the 'severe' level as increased wind speed was likely to lower the pollution level by Friday.

The taskforce met to discuss the high particulate matter levels that pushed the air quality into the 'severe' category.

But no additional measures were suggested as the air quality is likely to improve by Friday, it said.

"As per the IMD feedback, presently the wind speed is 10-15 kmph which is likely to increase tomorrow resulting in better dispersion. The air quality forecast model suggests significant drop in particulate matter concentration in the next two days. Therefore, no additional measures are suggested," the taskforce said.

According to the Indian Institute of Tropical Meteorology, the air quality is likely to improve marginally on Friday.

The ventilation index is marginally favourable for dispersion of pollutants at 4,500 sqm/second, IITM said.

Ventilation index is the speed at which pollutants can disperse. A ventilation index lower than 6,000 sqm/second, with an average wind speed less than 10 kmph, is unfavourable for dispersion of pollutants.

According to the SAFAR, the pollution level is likely to reduce by a few notches on Friday but air quality will continue to remain in the 'very poor' category in the next three days.

"Major reason for predicted increase is a decline in surface wind speed which will disperse pollutants slowly unlike yesterday. Other meteorological factors are also not very favourable," SAFAR said.