Environmental Protection Agency (6204J) October 1992 &EPA Acid Rain Program Environmental Benefits In order to reduce acid rain in the United States and Canada, Title IV of the Clean Air Act Amendments of 1990 established the Acid Rain Program. The program will cut sulfur dioxide emissions in half and substantially reduce nitrogen oxides emissions from electric utility plants. This fact sheet discusses the environmental effects of acid rain and the benefits that will accrue as a result of the required emissions reductions, and is one of a series containing information about the program. Acidic deposition, or acid rain as it is commonly known, occurs when chemically laden emissions re- act in the atmosphere with water, oxygen, and oxidants to form vari- ous acidic compounds. These com- pounds then fall to the earth in either dry form (such as gas and particles) or wet form (such as rain, snow, and fog). Sulfur dioxide (SO2), which is emitted primarily by coal-buming electric power plants, is the domi- nant precursor of acid rain in the United States. Emissions of nitrogen oxides (NOx) also play a role in the formation of acid rain and are signi- ficant in the formation of ground- level ozone. Electric utility plants account for about 70 percent of annual SO2 emissions and 30 percent of NOx emissions in the United States. Over 20 million tons of each of these two pollutants are emitted into the atmosphere each year. Acid rain causes surface water acidification and damages trees at high elevations (for example, red spruce trees above 2,000 feet in ele- vation). Air concentrations of sulfur and nitrogen species degrade visibil- ity in large parts of the country, in- cluding our national parks. In addition, acid rain accelerates the decay of building materials and Eaints, including irreplaceable uildings, statues, and sculptures that are part of our nation's cultural heritage. Finally, air concentrations of acidic aerosols (tiny droplets of sulfuric acid derived from SO2 emis- sions) may pose a risk to public health. Implementation of the acid rain provisions will confer significant benefits on the nation. Acid rain con- trol will allow acidified lakes and streams to recover so that they can or.ee again support fish life. Visibility will improve, allowing for increased enjoyment of scenic vistas across our country. Acid rain control will im- Erove the health of forests, particu- rly red sprace forests that populate the ridges of mountains from Maine to Georgia. I: will provide new safe- guards for our nation's cultural heritage through protection of his- toric buildings and monuments, and it will provide an insurance policy against the potential threat to public health posed by acidic aerosols. Surface Waters Acid rain primarily affects sensi- tive bodies of waters, that is, those that rest atop soil with a limit- ed ability to neutralize acidic compounds (called "buffering capac- ity"). Many lakes and streams exam- ined in a National Surface Water Survey (NSWS) suffer from chronic acidity, a condition in which water has a constant low pH level. The NSWS investigated the effects of acidic deposition in over 1,000 lakes larger than 10 acres and in thousands of miles of streams thought especially sensitive to acidification. Of tne lakes and streams surveyed in the NSWS, acid rain has been determined to cause acidity in 75 percent of the acidic lakes and about 50 percent of the acidic streams. In some sensitive lakes and streams, acidification has completely eradicated fish species, such as the brook trout, leaving these bodies of water barren. In fact, hundreds of the lakes in the Adirondacks surveyed in the NSWS have acidity levels indica- tive of chemical conditions unsuit- able for the survival of sensitive fish species. Emissions from U.S. sources con- tribute to acidic deposition in Canada. The soil in eastern Canada is very similar to the soil of the Adirondack Mountains. Lakes in eastern Canada are consequently ex- tremely vulnerable to chronic acidifi- cation problems. The Canadian government has estimated that 14,000 lakes in eastern Canada are acidic. Streams flowing over soil with low buffering capacity are equally as susceptible to damage from acid rain as lakes are. Approximately 580 of the streams in the Mid- Atlantic Coastal Plain* are acidic primarily due to acidic deposition. The New Jersey Pine Barrens area endures the highest rate of acidic streams in the nation with over 90 percent of the streams acidic. Over 1,350 of the streams in the The Mid-Atlantic Coastal Plain encompasses parts of the Piedmont and coastal plain in New Jersey, Delaware, Pennsylvania, Maryland, Virginia, and North Carolina. The Nlid-Atlantic Highlands extend from southeastern New York through most of Pennsylvania and include portions of Maryland. West Virginia, ana Virginia. The Mid-Appalachians include Virginia, West Virginia, Maryland, Pennsylvania, and North Carolina. Printed on paper that contains at least 50% recycled fiber. ------- Mid-Atlantic Highlands are acidic, primarily due to acidic deposition, while streams in the Mid-Appalachians are also under- going increasing acidification. Many streams in that area have already experienced trout losses due to the rising acidity Acidification is also a problem in areas that were not surveyed in federal research projects. For exam- ple, although lakes smaller than 10 acres were not included in the NSWS, there are from one to four times as many of these small lakes as there are larger lakes. In the Adi- rondacks, the percent of acidic lakes is significantly higher when it includes smaller lakes (26 per- cent) than when it includes only the NSWS target size lakes (14 percent). The acidification problem in both the United States and Canada grows in magnitude if "episodic acidification" (brief periods of low pH levels from snowmelt or heavy downpours, which can result in fish lulls) is taken into account. Lakes and streams throughout the United States, including western lakes, are sensitive to episodic acidification. In the Mid-Atlantic Highlands, the Mid-Atlantic Coastal Plain, and the Adirondack Moun- tains, about three times as many lakes and streams become tempo- rarily acidic during storms and snowmelt. Acid rain control will produce significant benefits in terms of low- ered surface water acidity. If acidic deposition levels were to remain constant over the next 50 years (the timeframe used for projection models), the acidification rate of lakes in the Adirondacks that are larger than 10 acres would rise by 50 percent or more. Scientists pre- dict, however, that the decrease in SO2 emissions required by the Acid Rain Program wul virtually elimi- nate emission-caused acidification in that area. Forests Acid rain contributes to forest degradation, especially in high- elevation spruce trees that populate the ridges of the Appalachian Mountains from Maine to Georgia, including national park areas such as the Shenandoah and Great Smokey Mountains national parks. Acidic deposition seems to impair the trees' growth in several ways; for example, acidic cloudwater at high elevations increases the susceptibil- ity of the red spruce to winter injury. 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 al- ready occurred as a result of acid rain. As acid rain moves through the soils, it can strip away vital plant nutrients through chemical reac- tions, thus posing a threat to future forest productivity. Visibility Sulfur dioxide emissions lead to the formation of sulfate parti- cles in the atmosphere. Sulfate particles account for more than 50 percent of the visibility reduction in the eastern part of the United States, affecting enjoyment at many of our national parks. The legislated reduction in SO2 emis- sions is expected to result in a 30- percent increase in visual range in the eastern part of the country. In the western part of the United States, nitrogen and carbon also play roles, but sulfur has been im- plicated as an important source of visibility impairment in many of the Colorado River Plateau na- tional parks, including the Grand Canyon, Canyonlands, and Bryce Canyon. Building Materials Acid rain is known to contribute to the corrosion of metals and deterioration of stone and paint in buildings, statues, and other struc- tures of cultural significance. The damage inflicted on cultural objects, such as statues or historic monu- ments, proves especially costly since a loss of detail caused by the corro- sive potential of acid nun seriously depreciates the objects' value to soci- ety. Dry deposition of acidic compounds can also dirty buildings # and other structures, leading to * increased maintenance costs. Given the very large number of buildings affected by wet and dry deposition, even a small impact on maintenance costs could translate into a very large savings to society. Health High levels of SO2 have been proven to cause or aggravate various types of lung disorders. These lune disorders, which affect a person's ability to breathe, have led to both increased morbidity (sick- ness) and mortality. Based on these concerns, SO2 has historically been regulated under the Clean Air Act. Additionally, studies at Harvard University have suggested a rela- tionship between acidic sulfate (a type of acidic aerosol) levels and increased levels of morbidity and mortality. While EPA continues to study the problem, SO2 emission reductions under the Acid Rain Program will reduce sulfate levels in the atmosphere, thereby pro- viding an insurance policy against this threat to public health. Clean Air for a Better Life 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 mil- lion-ton reduction in SO2 emissions should significantly decrease the acidification of water bodies and damage to forests and even allow these processes to be reversed. In addition, visibility will be signifi- cantly improved due to the cut- backs, ana the lifespan of building materials and structures of cultural importance should lengthen. Fi- nally, the reductions in emissions will help to protect public health. For More Information Write to: U.S.EPA Acid Rain Division (6204J) 401 M Street, SW. Washington, DC 20460 If you would like to receive other fact sheets on the Acid Rain Program, call the Acid Rain Hotline at 617-674-7377 or the EPA Public Information Center (PIC) at 202- 260-2080. 2 ------- |