LAHORE   -  Lahore has been declared the most polluted city in the world after the city’s Air Quality Index (AQI) went above 360.

The AQI data was released on Sunday, putting Lahore atop on the list of the most polluted cities globally. Karachi stands seventh.

Residents choking in acrid smog pleaded with officials to take action. Air pollution has worsened in Pakistan in recent years, as a mixture of low-grade diesel fumes, smoke from seasonal crop burn off, and colder winter temperatures coalesce into stagnant clouds of smog.

Lahore, a bustling megacity of more than 11 million people in Punjab province near the border with India, consistently ranks among the worst cities in the world for air pollution. In recent years residents have built their own air purifiers and taken out lawsuits against government officials in desperate bids to clean the air -- but authorities have been slow to act.

Air pollution in Lahore is caused by a combination of vehicle and industrial emissions, smoke from brick kilns, the burning of crop residue and general waste, and dust from construction sites. Other factors of air pollution include large scale losses of trees to build new roads and buildings.

Winter air pollution is worse due to temperature inversion, which results in a layer of warm air that is prevented from rising trapping air pollutants.