EPA-452/F-99-002) "I
September 1999.':
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Have you ever noticed that the scenic views in many
of our national parks are not as clear as they used to
be and, on some days, are not visible at all? Or have
you noticed that the skies in our cities are sometimes
very hazy? Visibility impairment, or haze, is one of
the most obvious effects caused by air pollution.
Visibility is a measure of how far and how well we
can see into the distance. The same pollutants
(primarily very small particles) that cause haze also
cause or contribute to significant health and
environmental problems across the United States.
Haze obscures the clarity, color, texture and form of
what we see. Haze is caused when light encounters
tiny pollution particles (sulfates, nitrates, organic
carbon, soot, and soil dust) and some gases (nitrogen
dioxide) in the air. Some light is absorbed by the
particles and gases and other light is scattered away
before it reaches an observer. More pollutants mean
more absorption and scattering of light, resulting in
more haze. Humidity (especially prevalent in the
East) magnifies the haze problem, because some
particles, such as sulfates, attract water and grow in
size, scattering light better than other particles.
Some haze-causing pollutants are formed when gases
emitted to the air form particles as they are carried
many miles from
the source of the
pollutants. Particles
that are formed
from gases include
sulfates, nitrates,
and some organic
carbon particles.
Other haze-causing
pollutants (mostly small
particles) are directly
emitted to the atmosphere
from sources such as
electric utilities and industrial fuel burning,
manufacturing processes, and vehicle emissions.
Natural sources such as forest fires and windblown
dust also contribute to haze.
Particles in the air can travel hundreds or thousands
of miles, contributing to the haze that causes visibility
impairment over broad regions of the United States.
This makes it important for states to work together
in solving the problem of regional haze.
Visibility is generally worse in the East than in the
West. In the eastern United States, reduced visibility
is primarily caused by sulfates from power plants and
other large, industrial sources. Emissions from these
same types of large, industrial sources also account
for much of the visibility impairment in the West.
However, other sources (such as woodsmoke from
burning or nitrates from auto emissions) play a more
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significant role in the West than in the East. Visibility
varies with the season and is generally worse during
the humid summer months. In our nation's scenic
areas, the visual range has been substantially reduced.
In eastern parks, average visual range has decreased
from 90 miles to 15-25 miles. In the West, visual
range has decreased from 140 miles to 35-90 miles.
less haze
Efforts to improve visibility also provide other health
and environmental benefits. Some of the same
particles that contribute to regional haze are also
linked to serious health and environmental effects.
• Exposure to very small particles has been linked
to increased respiratory illness, damage to lung
tissue, and premature death.
• Sulfates and nitrates contribute to the formation
of acid rain, which damages forests, erodes
building materials and monuments, and causes
lakes and streams to become acidic, making them
unsuitable for many fish.
• Other pollutants that contribute to haze also
help form ground-level ozone (smog) which can
trigger serious respiratory problems, and cause
significant damage to forests and ecosystems.
» Nitrogen oxide gases from electric utilities and
cars are a major contributor to increased nitrogen
loading in water bodies, particularly estuaries,
which upsets the chemical.balance of nutrients
used by aquatic plants and animals.
Acadia National Park
.on a dear day and
on a hazy day
Yosemite National Park
on a dear day and
on a hazy day
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EPA and
U.S. EPA
Office of Air Quality Planning & Standards
MD-15
Research Triangle Park, NC 27711
(919) 541-5551
Region 1
(Connecticut, Maine, Massachusetts, New
Hampshire, Rhode Island, Vermont)
John F. Kennedy Federal Building
One Congress Street
Boston, MA 02203
(617) 565-3476
(New Jersey, New York, Puerto Rico, Virgin
Islands)
290 Broadway
New York, NY 10007-3198
(212) 637-3725
(Delaware, District of Columbia, Maryland,
Pennsylvania, Virginia, West Virginia)
1650 Arch Street
Philadelphia, PA 19103-2029
(215) 814-2100
(Alabama, Florida, Georgia, Kentucky, Mississippi,
North Carolina, South Carolina, Tennessee)
61 Forsyth Street
Atlanta, GA 30303
(404) 562-9077
Regions
(Illinois, Indiana, Michigan, Minnesota, Ohio,
Wisconsin)
77 West Jackson Boulevard
Chicago, IL 60604-3507
(312) 353-2212
(Arkansas, Louisiana, New Mexico, Oklahoma, Texas)
Fountain Place, 12th Floor, Suite 1200
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 665-7200
(Iowa, Kansas, Missouri, Nebraska)
901 North Fifth Street
Kansas City, KS 66101
(913) 551-7020
(Colorado, Montana, North Dakota,
South Dakota, Utah, Wyoming)
999 18th Street, Suite 500
Denver, CO 80202-2466
(303) 312-6041
Region 8
(Arizona, California, Hawaii, Nevada,
Guam, American Samoa)
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1219
Region 10
(Alaska, Idaho, Oregon, Washington)
1200 Sixth Avenue
Seattle, WA 98101
(206) 553-4273
National Park Service
Air Resources Division
P.O. Box 25287
Lakewood, CO 80225
(303) 969-2074
U.S. FisSi and WJiWlife Service
Air Quality Branch
P.O. Box 25287
Lakewood, CO 80225
(303) 969-2617
U.S. Forest Service
20114th Street, SW
at Independence Avenue, SW
Washington, DC 20024
(202) 205-1473
I/I I
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The U.S. Environmental Protection Agency (EPA),
states, local governments, and other federal agencies
are working to reduce the pollution that causes
regional haze. Protecting and .improving visibility is
a crucial component of EPA's strategy for cleaner air.
Regional haze affects some of our nation's most
treasured areas, including the Grand Canyon,
Yellowstone, Acadia, and Shenandoah. To improve
visibility in national parks and wilderness areas, EPA
has issued regulations to reduce emissions that cause
haze. These regional haze regulations address a variety
of pollution sources that cause visibility impairment
across broad geographic areas. EPA's earlier
regulations focused on specific pollution sources that
contributed to local visibility problems. The regional
haze regulations call for states to establish goals for
improving visibility and to develop long-term
strategies aimed at returning visibility to natural
conditions.
The regional haze regulations also call for coordinated
efforts between the states to meet particulate matter
health standards. The program applies to all states,
based on evidence that very small particles can be
carried by the wind hundreds of miles. Each state is
to address its contribution to visibility problems in
national parks and wilderness areas both within and
outside its borders. EPA encourages states to work
in regional groups to develop and implement their
air quality plans.
Other air pollution reduction programs also contribute to
visibility protection. In developing strategies for regional
haze, states can take credit for emission reductions realized
through other programs, such as:
• Acid Rain Program - To help reduce acid rain, this
national program targets reductions in sulfur dioxide
' and nitrogen oxides from coal-fired power plants.
• National Ambient Air Quality Standards for Ozone and
Particulate Matter-To meet national health-protection
standards, state and local agencies are implementing
emission reduction programs.
• Regional Transport of Nitrogen Oxides - This program
targets reductions in emissions of nitrogen oxides in 22
eastern states. Nitrogen oxides can be transported long
distances and contribute to ground-level ozone formation.
• Tailpipe Emissions and Cleaner Fuels - Tighter tailpipe
emission standards for gasoline and diesel-powered
vehicles, along with programs for cleaner-burning fuels,
will further reduce air pollution.
• Air Toxics Program - Reductions in air toxics emissions
from industrial sources such as paper mills, steel mills
and incinerators can reduce haze-forming particles.
Denver on a clear day.
Denver on a hazy day.
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