United States - rj * EPA43,.
Environmental Protection June 1993
Agency
Air and Radiation (6204J) ~ •
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No Acid Rain Program
Acid Rain Program
1980 1990 2000 2010
Year
By the year 2010, the Acid Rain Program will result in
a 10-million-ton reduction in SOz emissions from 1980
levels.
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he Clean Air Act Amendments of
1990 call for major reductions in the
pollutants that cause acid rain. The
Amendments also establish a new approach
to environmental management. This brochure
'answers some of the most commonly asked
questions about the environmental benefits
of the Acid Rain Program.
What Is Acid Rain?
Acid rain is caused when sulfur dioxide and
nitrogen oxides—pollutants released primarily
from the burning of coal, oil, and other fossil
fuels—chemically react with other substances in
the atmosphere to form acidic compounds.
When these acidic compounds are carried down
from the atmosphere in rain, fog, snow, or dust,
they can end up in lakes and streams, on build-
ings and monuments, or on trees and land. They
can harm fish, damage high-altitude forests, and
contribute to the deterioration of buildings and
historical monuments. The pollutants that cause
acid rain also have been known to worsen
asthma and other lung ailments and to impair
visibility in many regions of the nation, includ-
ing the scenic vistas of our national parks.
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How Does Acid Rain Affect Lakes and
Streams?
When acid rain passes through soils or falls di-
rectly into our lakes and streams, it can increase
the acidity of the water, a process called addifica-
, tion. Increases in water acidity can impair the
ability of certain types, of fish and water plants to
reproduce, grow, and survive. In some acidified
lakes and streams, entire fish populations have
disappeared, leaving the bodies of water barren.
For example, many lakes in the Adirondack
1 Mountains of New York and many streams in the
Appalachian mountain region have experi-
enced losses of trout and other aquatic life due to
. acid rain.
The effects of acid rain can be either "chronic" or
! "episodic." Chronic acidity occurs when lakes and
streams cannot counteract the chemical changes
brought about by acid rain. This results in con-
stant high acidity levels in the water. Episodic
! acidity occurs only periodically, primarily as a re-
' suit of storms or snowmelts that empty large
amounts of acidic water into lakes and streams. In
the case of episodic acidity, lakes and streams
suffer from intense but short-lived increases
in acidity. In the spring, when such episodes
often occur, newly hatched fish can be killed.
\ Some lakes and streams are naturally more sensi-
tive to acid rain because they rest in soil that can-
; not neutralize acids. In the mid-1980s, the U.S.
Environmental Protection Agency (EPA) and other
federal agencies commissioned a National Sur-
face Water Survey to examine the effect of acid
rain in over 1,000 lakes and thousands of miles of
streams. From this survey, it was determined that
i of the water bodies found to be acidic, acid rain
: was the primary cause of the acidity. While the
acidity of some lakes and streams can be attrib-
uted to natural causes, most cases of acidity in
the United States result from acid rain.
Where Are the Acidified Lakes and
Streams Located?
According to the National Surface Water Sur-
'., vey, about 14 percent of the lakes (larger than
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. ID acres) in the Adirondack Mountains in New
York are chronically acidic, as are about 12 per-
cent of streams in the mid-Atlantic Highlands
(which include southeastern New York, most of
Pennsylvania, and portions of Maryland, West
Virginia, and Virginia) and the mid-Appalachi-
ans (which include Virginia, West Virginia,
Maryland, Pennsylvania, and North Carolina).
Other affected areas include Florida and the Up-
per Peninsula of Michigan. In addition, many
lakes and streams throughout the United States,
including those in the West, are sensitive to epi-
sodic acidification. The Canadian government has
estimated that 14,000 lakes in eastern Canada
are acidic, in part because of sulfur dioxide
emissions from U.S. utilities and industrial plants.
How Does Add Rain Harm Forests?
Acid rain can contribute to forest damage by im-
pairing the ability of some types of trees to grow
and fight disease. Acid rain also can strip forest
soils of essential nutrients, which hurts the pro-
ductivity of forests.
Which Forest Regions Are Most
Affected by Acid Rain?
Acid rain-has primarily impacted high-elevation
spruce trees that grow on the ridges of the
Appalachian Mountains from Maine to Georgia,
including spruce trees in the Shenandoah
National Park and the Great Smokey Moun-
tains National Park.
How Does Acid Rain Affect Visibility?
The chemical reactions that sulfur dioxide and
nitrogen oxides undergo in the atmosphere lead
to the formation of particles that can reduce the
distance we see and the clarity of our scenic
vistas. These particles account for over 50 percent
of the visibility problems in the eastern United
States. .In the West, such particles also have been
blamed for visibility problems in the Grand
Canyon and other national parks in the Colorado
River Plateau.
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Does Acid Rain Contribute to the
Decay of Buildings and Monuments?
Acid rain is known to contribute to the corrosior
of metals and to the deterioration and soiling ol
stone and paint on buildings, statues, and othei
structures of cultural significance. The damage
inflicted on cultural objects is especially costlj
since a loss of detail caused by the destructive
potential of acid rain seriously depreciates the
objects' value to society.
' Is Acid Rain Detrimental to Public Health"'
High levels of sulfur dioxide in the air have beer
proven to cause and aggravate various types oJ
lung disorders. These lung disorders, which
affect some people's ability to breathe, have led
to both increased disease rates and mortality ir
sensitive populations, such as young childrer
and the elderly. Low levels of acidic compounds
and acid aerosols commonly found in the air ir
the eastern United States can also pose healtb
problems, and EPA has been asked by a panel oJ
outside experts to investigate this issue.
What Are. the Benefits of Acid Rain
Legislation?
The substantial reductions in sulfur dioxide and
nitrogen oxides emissions that will take place
because of the Act will help improve environ-
mental and health conditions in the United
States. In particular, scientists have projected
that emissions reductions will increase the visual
range in the eastern United States by 30 percent
and reduce the deterioration of buildings and
monuments. In addition, scientists predict thai
the Acid Rain Program will virtually eliminate
acidity in the lakes and streams of the Adirondacks
caused by sulfur dioxide emissions and help
bodies of water and forests throughout the
United States recover from the effects of acid rain.
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