Lahore has topped the national air quality index, followed by Peshawar as the second most polluted city in the country. Multan ranks third, Rawalpindi fourth, Karachi fifth, and Islamabad sixth on the list. Lahore has topped the national air quality index, followed by Peshawar as the second most polluted city in the country. Multan ranks third, Rawalpindi fourth, Karachi fifth, and Islamabad sixth on the list.