Air quality in Pakistan's Lahore reached 'hazardous' levels Thursday:: It's prompted urgent calls for action to reduce pollution"The smog crisis is harming our health, causing respiratory issues and illnesses.

Air quality in Lahore reached hazardous levels this week, while other cities in South Asia also battle toxic pollution.

One doctor compared breathing in Pakistan's toxic air to smoking "dozens of cigarettes a day" as Lahore is the world's most polluted city this week.

A Pakistani province declared a health emergency Friday due to smog and imposed a shutdown in two major cities. Smog has choked Punjab for weeks, sickening nearly 2 million people and shrouding vast swathes of the province in a toxic haze.

Punjab province in Pakistan has declared a health emergency and closed two cities due to severe smog affecting nearly 2 million people.