Lahore: The capital of the Punjab province, Lahore, remained the most polluted city of the world for the second successive day on Sunday. The average air quality index (AQI) in the city was recorded at 650 early morning as stubble burning across the border continued and smoke entered Pakistan as a result of which breathing became difficult and smog reduced visibility. However, the Swiss IQAir recorded the AQI of Lahore early morning at 778. The Indian capital, Delhi, is the second most polluted city with average AQI at 429. The IQAir noted Delhi's AQI at 436.