Learn how air pollution can harm your health and the environment, and what EPA is doing to protect the air we breathe.

The Acid Rain Program (ARP), established under Title IV of the 1990 Clean Air Act (CAA) Amendments requires major emission reductions of sulfur dioxide (SO2) and nitrogen oxides (NOx), the primary precursors of acid rain, from the power sector. 

As part of the United States’ commitment to implementing the Montreal Protocol on Substances that Deplete the Ozone Layer, Congress amended the Clean Air Act to add provisions (under Title VI) for protecting the ozone layer.