Acid rain is rain, snow or fog that is polluted by acid in the atmosphere and damages the environment. Two common air pollutants acidify rain: sulphur dioxide (SO₂) and nitrogen oxide (NO_X). When these substances are released into the atmosphere, they can be carried over long distances by prevailing winds before returning to earth as acidic rain, snow, fog or dust. When the environment cannot neutralize the acid being deposited, damage occurs. 

Acid rain is a problem in Ramford County because many of the water and soil systems in this region lack natural alkalinity—such as a lime base—and therefore cannot neutralize acid naturally. Areas now being considered for the development in the Renapi Indian enclave are hardest hit because their water and soil systems cannot fight the damaging consequences of acid rain. In fact, more than half of Ramford County consists of susceptible hard rock (i.e., granite) areas that cannot neutralize the effects of acid rain. If the water and soil systems were more alkaline—as in western parts of the country—they could neutralize or "buffer" against acid rain naturally.

There also is a concern about the impact of acid rain on forest soils. There is good reason to believe that long-term changes in the chemistry of some sensitive soils may have already occurred as a result of acid rain. As acid rain moves through the soils, it can strip away vital plant nutrients through chemical reactions, thus posing a potential threat to future forest productivity.

By reducing SO2 emissions by such a significant amount, the Clean Air Act promises to confer numerous benefits on the nation. Scientists project that the 10 million-ton reduction in SO2 emissions should significantly decrease or slow down the acidification of water bodies and will reduce stress to forests. In addition, visibility will be significantly improved due to the reductions, and the lifespan of building materials and structures of cultural importance should lengthen. Finally, the reductions in emissions will help to protect public health.