4. We experience brown smog, especially in Denver and LA.
5. It is harmful because brown smog is composed of NOx's which react with water vapor in the atmosphere and create acid rain.
6. One result of air pollution is acid rain.
7. Acid rain.
8. Acid rain harms our environment by decreasing the pH of the soil which can harm plant life and bacteria, disrupting the ecosystem.
9. Americans are improving air quality by passing laws such as the Clean Air Act of 1990 which puts limits on the amount of air pollutants cars, factories, ect can release into the atmosphere.
Side note: if you enjoy learning about this sort of thing or how humans impact the world, and haven't taken AP Environmental Science you totally should. It's a very eye opening class and I enjoyed it very much this year!