Delhi's air quality continued to remain in the 'very poor' category Thursday due to unfavourable meteorological conditions that slowed down dispersion of pollutants even as authorities forecast "significant deterioration" in pollution levels over the weekend.
The overall air quality index (AQI) of Delhi was recorded at 353, according to Central Pollution Control Board (CPCB) data.
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'.
The CPCB said seven areas in Delhi -- Ashok Vihar, Anand Vihar, Jahangirpuri, Mundka, Rohini, Vivek Vihar and Wazirpur -- recorded 'severe' air quality.
Twenty areas in the national capital recorded 'very poor' air quality while it was 'poor' in six areas, it said.
The level of PM2.5 -- particles in the air with a diameter of less than 2.5 micrometres -- was recorded at 206 and the PM10 level was recorded at 360, it said.
In NCR, Ghaziabad, Faridabad and Noida recorded 'very poor' air quality while Gurgaon fell into the 'poor' category, CPCB data showed.
According to the Indian Institute of Tropical Meteorology, the wind speed and ventilation index are "extremely unfavourable" for dispersion of pollutants.
Ventilation index determines how fast pollutants can get dispersed.
The ventilation index of around 6,000 sqm/second gets rid of pollutants, but it fell to 2,500 sqm/second on Thursday in the city.
According to the Centre-run System of Air Quality and Weather Forecasting (SAFAR), the air quality is 'very poor' and likely to improve due to a slight increase in the wind speed. It will, however, remain in the 'very poor' category for the next two days.
"Due to cold front up in the north, the wind speed has increased, so a decline (in pollution levels) is expected. However, at the time of withdrawal (of high wind speed) after two to three days, a lot of moisture may enter Delhi which is not favourable for the air quality. The contribution from stubble burning is nil," the SAFAR said.
The government agency SAFAR further said the air quality of the national capital is expected to "significantly deteriorate" on Sunday due to a decline in temperature which might lead to entrapment of pollutants.
It, however, said the air quality even after "significant deterioration" is likely to stay in the 'very poor' level and not reach the 'severe' category.
The CPCB has come out with a list of nearly six lakh diesel and petrol vehicles that are over 10-years-old and will not be allowed to ply in Haryana.
The list gives details of the registration mark series, name of the authority and registration numbers of these vehicles plying in Haryana, including NCR cities of Gurgaon, Sonipat and Bahadurgarh.
As many as 2,87,613 petrol vehicles that were older than 15 years have been listed while 3,07,453 diesel vehicles more than 10-years-old have also been named, the CPCB said on its website.
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