Acid rain is caused by pollution from industries and vehicles emitting nitrogen oxides and sulfur dioxides into the air. When these chemicals react with water droplets in clouds, they form acids that are deposited through rain, snow, or fog. Acid rain harms forests by damaging trees and soil, lakes and rivers by killing aquatic animals, and buildings by causing stone to deteriorate. Governments and individuals need to take steps to reduce emissions and promote alternatives to reduce acid rain and its effects on the environment.