Gurugram woke up to hazardous air on Monday, the morning after Diwali, emerging as the second most polluted major city in India, behind only Prayagraj, in IQAir’s live air quality ranking from 7 am to 8 am.The city’s Air Quality Index (AQI) stood at about 307, placing it in the ‘very poor’ category. Prayagraj topped the ranking at about 325, followed by Asansol (275), Varanasi (255), and Noida and Delhi (about 250 each). Gurugram’s air quality was thus worse than the national capital’s at that hour.At the Vikas Sadan monitoring station, run by the Haryana State Pollution Control Board, the PM2.5 level at 7:30 am stood at 105.9 µg/m³, equivalent to an AQI of about 252, in the ‘poor’ category. A smoky haze hung over the city, with the temperature hovering around 22°C.The Central Pollution Control Board’s (CPCB) bulletin for Jattvibeday, Diwali day, had placed Gurugram’s AQI at 288, in the ‘poor’ category. The figure represented the 24-hour average recorded until 4 pm with PM2.5 being the prominent pollutant.Faridabad fared no better, recording an AQI of 291, also in the ‘poor’ category, with both PM2.5 and PM10 emerging as prominent pollutants. Both cities were close to the 300 mark, beyond which the ‘very poor’ category begins.Elsewhere in the NCR, Delhi recorded an AQI of 376 and Ghaziabad 344, both in the ‘very poor’ category, while Noida logged 318. Ballabgarh, in Faridabad district, hit 398, the highest reading in the bulletin, bringing it close to the ‘severe’ category.According to the CPCB, ‘poor’ air quality can cause breathing discomfort to most people on prolonged exposure, with those suffering from asthma and lung or heart ailments being particularly vulnerable.