Delhi's air quality remained in the severe category for the third consecutive day on Monday, prompting authorities to impose a three-day ban on industrial activities in pollution hotspots and construction work across Delhi-NCR.
The city is facing its highest pollution level since Diwali. While the Central Pollution Control Board (CPCB) data showed the overall air quality index (AQI) at 'severe' level of 448, the Centre-run System of Air Quality and Weather Forecasting (SAFAR) showed an AQI of 468.
In view of the prevalence of severe pollution in the national capital, the CPCB recommended to the Supreme Court-appointed Environment Pollution Control Authority (EPCA) to shut down industries located in hotspot industrial areas of Wazirpur, Mundka, Narela, Bawana, Sahibabad and Faridabad.
They will remain closed until Wednesday, said EPCA Chairperson Bhure Lal.
In a letter to Delhi Chief Secretary Vijay Kumar Dev, Lal also directed him to ban all construction activities in the national capital, Faridabad, Gurugram, Ghaziabad and Noida till Wednesday.
The Delhi Pollution Control Committee said the ban comes into force from Monday itself and it is sending letters to industries and construction authorities to immediately halt the activities.
The EPCA directed the traffic police to deploy special teams and ensure congestion-free traffic flow particularly in identified high traffic corridors.
The agencies concerned have also been asked to ensure strict action against illegal industries, intensify ground action and make all efforts to control polluting activities, particularly waste burning.
"The ventilation index which allows dispersion (of pollutants) is extremely poor and it is expected that these conditions will prevail for the next two days," Lal said in the letter.
In light of this and the expected weather conditions for the coming few days, the CPCB task force has made these recommendations, which, the EPCA directs, should urgently be complied with, he said.
On Monday, Delhi's air quality was recorded at 448 which falls in the 'severe' category, the CPCB said.
Thirty areas in the city recorded 'severe' air quality while it was 'very poor' in five areas, it said.
In NCR, Noida recorded the worst air quality with an AQI of 464. Faridabad and Ghaziabad also recorded 'severe' air quality and Gurgaon recorded very poor air quality, the data showed.
The overall PM2.5 level -- fine particulate matter in the air with a diameter of less than 2.5 micrometer -- was recorded at 407 and the PM10 level at 581 here, the CPCB said.
Delhi's air quality turned 'severe' on Saturday. The national capital recorded its second highest pollution level of the year on Sunday with an AQI of 450.
According to the SAFAR, the overall air quality in Delhi is expected to remain in severe range until Tuesday.
"Recovery got delayed mainly due to slowing of wind speed leading to persistence of fog which rapidly multiplied finer particles leading to rapid increase in PM2.5 and even PM1 (fine particulate matter in the air with a diameter of less than 1 micrometer)," the SAFAR said.
"Improvement is expected from late Tuesday evening only when radiation fog get dissipated with sufficient sunshine," it said.
According to the Indian Institute of Tropical Meteorology (IITM), the air quality is likely to improve on Tuesday, but will remain in the upper end of the 'very poor to severe' category.
"The wind speed and ventilation index are highly unfavourable for dispersion of pollutants," it said.
Ventilation index is the speed at which pollutants can get dispersed. A ventilation index lower than 6000 sqm/second, with average wind speed less than 10 kmph, is unfavourable for dispersion of pollutants.
The index was 4500 sqm/second on Monday, the IITM said.
In a health advisory, the SAFAR asked Delhiites not to rely on common dust masks for protection.
The agency has advised people to avoid all outdoor activities, such as taking walks.
"If the room has windows, close them, if the air conditioner provides a fresh air intake option then choose it, avoid burning anything such as wood, candle or even an incense," it said.
The advisory also recommended frequent wet mopping and using masks known as N-95 or P-100 respirators only for outdoor activities.
"Do not rely on dust masks for protection," the advisory added.