Skies over the national capital today were a smoky grey as the sun struggled to shine through the haze with the air quality deteriorating and slipping into 'severe category' in several places in the city.<br />'' <br />'' At 12.30 p.m., the city's overall air quality index was 390 marginally better than yesterday's high of 397 at 8 p.m., according to the Central Pollution Control Board. Pollution levels in the satellite towns of Ghaziabad (429), Greater Noida (418) and Noida (427) were worse.<br />'' <br />'' Delhi's air quality took a hit after Diwali night due to a combination of firecracker emissions, stubble burning and non-favourable meteorological conditions. Since then, pollution levels have been oscillating between the lower end and the higher end of the very poor category. On Diwali night, a large number of revellers brazenly flouted the Supreme Court-enforced two-hour limit for bursting crackers.<br />''  <br />'' The Supreme Court had also ordered that only green firecrackers, which cause 30 per cent less pollution, can be manufactured and sold, but an official of Delhi Pollution Control Committee said a large number of illegal crackers were burst on Diwali.