The main sources that cause air pollution today are things like: Gasses from vehicles, toxic chemicals, smoke from factories, pet hair, and Randon. (Randon is a colorless and odorless gas that is radioactive).
All those things cause: Air pollution, acid rain, and ozone. (Ozone is a toxic form of oxygen).
I know all this because I just learned it and wrote an essay on it yesterday.
Hope I helped!
- Amber