New Delhi: The city's air quality on Tuesday turned severe after a break of seven days, making it the fourth such day this month.The air quality index (AQI), on a scale of 0 to 500, was recorded at 418 at noon and 417 at 2pm. According to Central Pollution Control Board (CPCB), Delhi's 4pm AQI, considered the day's standard reading, stood at 412, worsening from 373 (very poor) a day earlier. The index...