Here's an aerial view at the smog in Tianjin. It's not pretty.
It is safe to stay at home rather than go to school.
Li Jingren, 15
The air pollution has been blamed on China's reliance on coal and emissions from old cars.
The smog isn't just ugly -- particles in the air can damage lung tissue. Hospital waiting rooms have been packed with children in face masks, The Associated Press reports. Winter tends to be smoggier than most seasons as people use more energy to heat their homes.
Here's a look at how the smog is affecting citizens.
Severe smog continued to shroud northern China and even worsened on Monday, PM2.5 reading in Shijiazhuang exceeded 1,000 mg per cubic meter pic.twitter.com/YuxMzs9MAR