The most air pollution is happening in major cities in all parts of the world. Cities aren't the best place to live when it comes to air pollution because of smog. Smog is a type of air pollution which has affected human heath the most of all air pollution in ever recorded history. It is caused by water molecules coming together with smoke particles in the atmosphere to form a dense fog. The smoke particles are often from burning coal. London had a severe fog in 1952 in which 4,000 deaths occurred. This was of the type of smog shown above.

Another type of smog is ice smog. Ice smog is when smoke particles and ice crystals combine. Ice smog happens only in high places, like mountains, and at very low temperatures.

Something else that happens from air pollution is acid rain. People call it acid rain because there is some acid in it which can destroy buildings, waterways, and many crops. Acid rain is when pollution is carried in the atmosphere for a long period of time. Then comes down with rain.
Everything we just talked about is from people polluting the air. If you don't want things like this happen as much as they are, think about ways you can stop them! You can help!