Hi there!
One of the main causes of air pollution is smoking.
Smoking affects not only humans, but pets and animals as well. Animals can get cancer too!
Another big cause of pollution is cars. Gasoline of course comes out into the air after it is used. It also affects animals.
A lot of people know that we should change this, but hardly anyone is really doing anything to try and stop it.
I know this is a short answer, but I hope it helps!