Acid rain is the popular term for precipitation that has an abnormally high acid content.
This term is used to indicate that any form of precipitation can contain acid gases and cause serious pollution problems. A very small amount of acid gas is produced by natural environmental processes. Acid rain damages the delicate ecosystems of lakes and rivers and their plant life. Acid rain has been linked to the deterioration of forests in both North America and Europe. It can also have significant detrimental effects on human health.