The EPA estimates that more than 65%, or over 13 million tons per year, of SO2 production in the U.S. comes from electric utilities, 93 percent of which is produced by coal power plants. In China, the world’s largest consumer of coal, approximately 22.5 million tons of sulfur were released in 2004, and over 30% of the country now experiences acid rainfall.

Acid rain is rain saturated with chemicals like sulfur dioxide and nitrogen oxide, which causes acidification of lakes and streams and contributes to the damage of trees at high elevations and many sensitive forest soils. In addition, acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage. Prior to falling to the earth, sulfur dioxide and nitrogen oxide gases and their particulate matter derivatives—sulfates and nitrates—contribute to visibility degradation and harm public health.

In 2010, plant experts, scientists, environmentalists and ranchers said they believe sulfur dioxide pollution from coal-fired power plants is slowly killing vegetation across Texas. Sulfur dioxide has been known to kill vegetation in other parts of the country. In Texas, the deaths of pecan trees, oaks, elms and willows have been documented. In Central Texas, not far from a power plant operated by the Lower Colorado River Authority, pecan growers say thousands of trees have died and nut production has steadily decreased since the plant began operating in 1979. After consulting experts, the growers believe the plant's sulfur dioxide emissions are to blame. The U.S. Environmental Protection Agency has toured some of the farms and is reviewing the data.

Winds can blow SO2 and NOX over long distances and across borders making acid rain a problem for everyone and not just those who live close to these sources.