The port city of Karachi joined Lahore on Thursday as having unhealthy air after an air quality index reading of 494 was recorded.
The air quality in Karachi is among the worst in the world, ranking it among the most polluted cities.
When the Pollution Index is between 154 and 200, it is considered dangerous, and when it is beyond 300, it is considered very dangerous.
According to the Air Quality Index, Pakistan has the third-worst air quality of any country in the world.
While Lahore scored a 168, placing it eighth on the list of the world’s most polluted cities.