Do you remember the August 2003 major blackout that shut down the electrical grid for over 50 million residents in northeastern North America?  Over 100 fossil-fuel burning electric generating power plants were shut down.  Fortunately, a meteorologist from the University of Maryland recognized an opportunity for scientists to see how much pollution fossil fuel plants produce.  His team flew an aircraft over the middle of the blackout zone 24 hours after the power had gone down.  One flight made its measurements outside the blackout area—over Cumberland, Maryland, and nearby parts of Virginia—and the other over Selinsgrove, Pennsylvania, in the heart of the blackout.  These measurements were compared to data collected a year ago under similar atmospheric conditions. 


They found that the levels of sulfur dioxide and ozone were 90 and 50% lower, respectively, in Selinsgrove.  Haze was down by 70%. Visibility increased by 20 miles. In the Washington, D.C., area, the skies were actually bluer, and a dangerous “code red” air quality rating that was predicted for that day never materialized.  In contrast, the pollution levels over Cumberland were essentially the same as the 2002 readings from Selinsgrove.


With all the technological advancements over the last century, one thing that has not changed very much is our reliance on fossil fuels, in particular, dirty coal, to generate electricity.  More than half of the electricity generated in the United States comes from coal.  Fossil-fuel power plants (oil, natural gas and coal) are the number one point source of pollution in the U.S.  Here is a summary of their pollutants:


Sulfur Dioxide (SO2):  Coal-fired power plants are the largest single source of sulfur dioxide (SO2), releasing about 67% of the total SO2 pollution each year.  SO2 is a major contributor to smog (ground level ozone) and acid rain.


Nitrogen Oxides (NOx):  Power plants are second only to automobiles as the greatest source of NOx emissions, accounting for 25% of all NOx  emissions.  When nitrogen oxide (NOx) reacts with volatile organic compounds (or, hydrocarbons) and sunlight, smog (ground level ozone) forms.  This ground level ozone should not be confused with the naturally occurring, beneficial high atmospheric ozone layer, which filters the sun’s ultraviolet rays.


Acid Rain:  In the U.S., coal-fired power plants are the single largest source of SO2 pollution (66%) and the second largest source of NOx pollution.  Acid rain, or acid deposition, occurs when sulfur dioxide (SO2) and nitrogen oxide (NOx) react with water and oxygen in the atmosphere to form acidic compounds, most commonly sulfuric and nitric acid.  These acidic compounds then either mix with natural precipitation and fall to the earth as acid rain, or remain dry and then settle to the ground.


Mercury and other hazardous air pollutants:  Coal-fired power plants are the largest single manmade source of mercury and the largest unregulated source of mercury pollution.  In smokestack tests, coal-fired power plants were also found to release 67 air toxics, many of which are known or suspected carcinogens and neurotoxins.


Particulate Matter:  Power plants release about 50% of all particulate sources.  SO2 can combine with nitrogen oxide (NOx) and other particles to form particulate matter, which is also known as soot.  Particle pollution is the number one cause for haze, or reduced visibility, in the U.S.


Carbon Dioxide:  Power plants emit 40% of total U.S. carbon dioxide pollution, the primary pollutant responsible for global warming.  Burning fossil fuels such as coal releases carbon dioxide (CO2) pollution, making energy use the single largest source of greenhouse gases in the U.S. and the world.


With the proliferation of coal-burning power plants located on the windward side of the Blue Ridge Mountains, these pollutants, generated both in the Northeast and Midwest, are carried by winds eastward affecting the Appalachian Trail, Shenandoah and Great Smoky Mountains National Parks, our National Forests and other hiking destinations where they reduce visibility, adversely affect health, generate acid rain, and contribute to climate change.


Shenandoah National Park (SHEN) has among the highest ground level ozone levels of all National Parks.  It has frequently exceeded maximum hourly National Ambient Air Quality Standards (NAAQS) for ozone concentrations (43 times during 1997-1999) and in 2004 had a portion of the park designated by the Commonwealth of Virginia as a non-attainment area for ozone.  Foliar damage is noted among sensitive plants, including black cherry, yellow poplar, red maple, sassafras, and white ash, among others.  Existing models project that future growth of white ash will be affected by current ozone levels while yellow poplar growth will be affected in the future with any increase in ozone exposure.


Ozone pollution in Great Smoky Mountains National Park (GRSM) far exceeds SHEN in severity.  At GRSM, for example, ozone pollution has violated NAAQS standards more than 175 times since 1998 and is damaging 30 species of plants.


In 2003, SHEN received the highest sulfate and nitrate deposition levels of any Class I National Park in the country, a title often held by GRSM.  Sulfate and nitrate containing pollutants are normally taken up through roots in soil depositions.  These pollutants acidify the soil and make aluminum more available to root uptake.  Such aluminum uptake can be toxic to plants.  Additionally, high elevation spruce are known to absorb some sulfates through leaf stomata, causing foliar injury.  From 1984-1999, sulfate concentrations increased in the SHEN region by 27%.  60 to 80% of the visibility impairment in these parks is attributable to sulfate particles formed from sulfur dioxide emissions from fossil fuel power plants. 


The GRSM vies with SHEN in receiving the highest sulfur and nitrogen deposits of any monitored national park.  The average acidity (pH) of rainfall in GRSM is 4.5, 5-10 times more acidic than normal rainfall (5.0-5.6). Clouds with acidity as low as 2.0 pH have been documented in the high elevation forests (vinegar has a pH of 2.4). 


Acid rain, or acid deposition, is most concentrated during high flow events.  During such events, high deaths within the macroinvertebrate aquatic ecosystem can be experienced.  In streams with a quartzite or sandstone bedrock (which have low buffering capacities), such events can be particularly detrimental to native fish populations.  These conditions are most prevalent in the south district of SHEN.


Fine mass particulates is another monitored pollutant in both SHEN and GRSM.  Fine particles create haze by scattering and absorption of visible light.  Chemical components of the fine mass particulates include ammonia sulfate, ammonia nitrate, organics, carbon and fine soil.  Approximately 78-86% of total light extinction in the Blue Ridge Mountains is the result of man-made sources. 


Annual visibility at SHEN now averages 23 miles; only 20% of the original visibility.  During the summer, visibility averages 12 miles, while winter visibility averages 40 miles.


GRSM now averages 25 miles, compared to former natural conditions of 93 miles. During severe haze episodes, visibility at both GRSM and SHEN have been reduced to less than one mile.  The burning of fossil fuels produces airborne sulfate particles, which also contributes to scattering light and degrading visibility.

So, we’ve established that fossil-fuel power plants, most notably, coal-burning power plants, are a significant health and environmental hazard to our eastern deciduous forests.  The question now becomes, what is being done by our federal government to control these pollution sources?


In 1970 the Clean Air Act (CAA) was passed to help protect people from dangerous air toxins, officially known as hazardous air pollutants. The Clean Air Act requires the Environmental Protection Agency (EPA) to control 187 different types of toxic pollutants to protect human health and the environment.  To control toxic air pollution, the EPA first determines the source of the pollution, such as power plants, and then determines what actions the sources need to take to help reduce the amount of toxic pollution they release into the air. EPA's standards are meant to ensure that power plants and other sources of toxic pollution implement the greatest reductions possible of the air toxics, or the maximum achievable level.


In 1997, amendments to the CAA were enacted to further strengthen pollution controls.  For example, the amendments established a national goal of cleaning up the air over national parks and wildlands, designated as Class I areas. Class I designation affords the greatest degree of air quality protection under the CAA.


Additionally, New Source Review (NSR) provisions of the CAA amendments were added to ensure that old polluting facilities eventually caught up with the pollution reductions achieved by more modern industrial facilities.  NSR set up standards for technological improvements of pollution control systems, which would be required when facilities make construction expansions, resulting in significant new pollution.


And, how have these legislative actions fared in controlling air pollutant sources?


In 2002, President Bush announced his ‘Clear Skies’ initiatives.  Sadly, these Clear Skies initiatives would weaken many parts of the Clean Air Act and would result in the emission of significantly more air pollutants than currently allowed.  The details for three of the most significant pollutants are listed below.


Clear Skies allowable pollutants




Amount above existing CAA

450,000 tons

1,000,000 tons

10 tons

Percent allowed above existing CAA




Delay in implementation beyond existing CAA

8 years

6 years

10 years


Additionally, Clear Skies creates a loophole exempting power plants from being held accountable to the Clean Air Act's New Source Review (NSR) standards.  This will allow old coal-burning power plants to rebuild without installation of modern air pollution control devices (best available retrofit technology or BART), which was required under existing CAA legislation.


Clearly, if we are interested in improving the air quality that currently threatens our National Parks, human health and our environment, we must direct our attention to these major sources of pollution. 


The good news from the 2003 blackout was the extent and rapidity of the improved air quality resulting from the elimination of the fossil-fuel burning power plant emissions.  This means that if we install more efficient pollution control devices on these power plants, a major source of pollution can be significantly reduced. 


While many of our environmental issues may be complex and difficult to resolve, air pollution is not one of them.  The technology exists today to remove a significant amount of pollutants from our air.  We can improve visibility from our Parks, reduce plant and animal injury from acid deposition, ozone and mercury emissions, and reduce global warming, all by enforcing the regulations currently on the books that have been promulgated from the ground-breaking Clean Air Act and it’s amendments.


That goal has yet to be reached.