Causes

Sulphur dioxide (SO₂) and nitrogen oxides (NO_x) are the primary causes of acid rain.

In the U.S., about 2/3 of all SO₂ and 1/4 of NO_x comes from electric power generation that relies on burning fossil fuels like coal.

Coal accounts for most of the sulphur dioxide and a large portion of the nitrogen oxide emissions.

Nitrogen oxides are formed when any fossil fuel is burned.

Once airborne, these gases react in the atmosphere with water, oxygen, and other chemical to form various acidic compounds.

The result is a mixed solution of sulphuric acid and nitric acid.

The problem is mesoscale; entire countries could be affected.