Air quality in Delhi remained ‘severe’ for the third consecutive day on Wednesday as thick haze engulfed the national capital after mild rains added to pollution woes, said authorities. An overall air quality index (AQI) was recorded 413 by the Central Pollution Control Board (CPCB). An AQI between 201 and 300 is considered 'poor', 301 and 400 'very poor' and 401 and 500 'severe'. The AQI on Monday was recorded at 412 and on Tuesday it was at 415.
Neighbouring Ghaziabad and Noida also recorded 'severe' air quality. Ghaziabad's air quality was the worst at an AQI of 429, the CPCB data showed. Faridabad recorded 'very poor' air quality, it said.
Twenty-nine areas in Delhi recorded 'severe' air quality, while eight areas were at 'very poor', it added.
Rohini, Bawana, Ashok Vihar and Wazirpur edged towards 'severe plus emergency' category, the CPCB said.
The overall PM2.5 level -- fine particulate matter in the air with a diameter of less than 2.5 micrometre -- was recorded at 257 and the PM10 level at 423, it said.
According to the Centre-run System of Air Quality and Weather Forecasting (SAFAR), meteorological conditions leading to insufficient rain led to deterioration of the air quality.
"There is a fall in temperature and good amount of moisture is present in the air. Moist air is passing over Delhi's cool surface leading to fog formation and calm winds are not allowing pollutants to disperse," the SAFAR said.
The air quality is likely to remain under 'severe' category for next two days, the IMD said. Situation is likely to improve after that when wind speed picks up.
The relative humidity was recorded on Wednesday at 98 per cent, MeT officials said.
"Levels of gaseous pollutants, NOx and CO, are forecast to be enhanced, up to moderate range, after a long time due to a fall in boundary layer height and reduced vertical mixing," it said.
Authorities said a thick haze engulfed the national capital.
The maximum ventilation index is likely to be 3,500 sqm/second from December 10-12, the Indian Institute of Tropical Meteorology said.
The ventilation index lower than 6,000 sqm/second with average wind speed less than 10 kmph is unfavourable for dispersion of pollutants.
The wind speed, ventilation index and higher moisture are highly unfavourable for dispersion of pollutants, the IITM added.
According to experts, even healthy people find it hard to breathe when air quality level is at 'severe' and doctors advise physical activity to be kept at a minimum.