A thick haze engulfed Delhi Wednesday as the air quality in the national capital remained "severe" for the third consecutive day with mild rains adding to pollution woes even as authorities directed municipal bodies to carry out special drives in severely polluted areas.
The authorities had on Tuesday said that they would undertake stringent measures if air pollution levels remained severe in the next 48 hours.
A Central Pollution Control Board (CPCB)-led task force directed all municipal corporations and other agencies concerned in the Delhi-NCR to carry out a special drive and enforce corrective actions, particularly in the areas battling severe pollution levels.
The CPCB recorded an overall air quality index (AQI) of 413 on Wednesday. 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.
According to experts, even healthy people find it hard to breathe when the air quality level is at "severe" and doctors advise physical activity to be kept at a minimum.
Neighbouring Ghaziabad and Noida also recorded "severe" quality air. 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 and in eight areas, it was "very poor", the CPCB added.
Rohini, Bawana, Ashok Vihar and Wazirpur edged towards "severe plus emergency" category, the agency said.
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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.
The Centre-run System of Air Quality and Weather Forecasting (SAFAR) said meteorological conditions leading to insufficient rain led to deterioration in 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," it said.
According to the IMD, the air quality is likely to remain in the "severe" category for the next two days. 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.
The authorities said a thick haze has engulfed the national capital.
According to the Indian Institute of Tropical Meteorology, the maximum ventilation index is likely to be 3,500 sqm/second from December 10-12.
A 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 CPCB data, 19 areas in Delhi have been identified where a special anti-pollution drive would be carried out.
The CPCB-led task force emphasised that implementing agencies must ensure strict enforcement of the Graded Response Action Plan and effectively deal with violations.
The areas identified in Delhi are Anand Vihar, Ashok Vihar, Bawana, Burari Crossing, CRRI Mathura Road, DTU, Dwarka-Sector 8, Jahangirpuri, Jawaharlal Nehru Stadium, Nehru Nagar, Rohini, Sonia Vihar, Wazirpur, Mandir Marg, Narela, Okhla Phase 2, Patparganj, Sirifort and Vivek Vihar.
The areas in NCR are Faridabad Sector- 16A, Baghpat New Collectorate, Yamunapuram, Vasundhara, Knowledge Park - III, Hapur Anand Vihar, Sector - 125 in Noida and Sector - 62 in Noida.