Worsening air pollution sickened an estimated 1.8 million people in Pakistan's eastern Punjab province in the past month, health officials said Tuesday, as schools across the province were ordered to close for five days to protect children's health.

The U.N. children’s agency is warning that the health of 11 million children in Pakistan’s eastern Punjab province is in danger because of air pollution that experts say has become a fifth season in recent years.

Pakistan's province of Punjab set up a "smog war room" to tackle severe pollution, officials said, as poor air quality turned its capital of Lahore into the world's most polluted city and forced the closure of some educational institutions.

"Over 1.8 million people visited hospitals and private clinics in the smog-hit districts in Punjab in the past 30 days, and most of them had been suffering from respiratory-relate