Record-breaking levels of thick, toxic smog that have shrouded eastern Pakistan and northern India since last month can be seen in striking satellite imagery.

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.

A thick blanket of smog continued to suffocate several cities in Pakistan’s Punjab province, spreading its toxic reach and severely disrupting transportation. As Lahore remained the world’s most polluted city,