What is acid rain?

Acid rain is a problem that affects us all—whether it is damaging the family car, defacing historical statues, harming trees in a once-beautiful mountainous forest, or destroying the fish population in a lake. Acid rain is rain, fog, or snow from the atmosphere that contains higher than normal amounts of nitric and sulfuric acids. Acid rain comes from both natural sources, such as volcanoes and decaying vegetation, and human-made sources, such as emissions of sulfur dioxide and nitrogen oxides, which come from fossil fuel combustion. In the United States, most of these emissions come from electric-power generation that relies on burning fossil fuels, like coal. Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form acidic compounds. The result is a mild solution of sulfuric acid and nitric acid. When sulfur dioxide and nitrogen oxides are released from power plants and other sources, the wind blows these compounds across state and national borders, sometimes over hundreds of miles.