The Air Quality Index (AQI) of cities in Uttar Pradesh deteriorated on Sunday, with some of them recording the worst air quality in the country, CPCB data has revealed. Lucknow recorded an AQI reading of 406 on Sunday, becoming the second-worst polluted city in the country. Lucknow was followed by Moradabad (391), Kanpur (364), Bulandshahr (364) and Varanasi (358).