&EPA
Nitrogen:
Multiple and
Regional Impacts
-------
United States Clean Air EPA-430-R-01-006
Environmental Protection Market Programs February 2002
Agency
For more copies of this document, please contact:
US EPA Clean Air Markets Division
1200 Pennsylvania Ave, NW
Mail Code 6204N
Washington, DC 20460
(202) 564-9620
www.epa.gov/airmarkets
-------
Contents
Introduction 1
Need Fora Regional Approach 2
Structure of the Report 3
Nitrogen Sources 4
Natural Sources 4
Man-made Sources 5
Multiple Transport and Exposure Pathways 8
Atmospheric Concentrations 8
Nitrogen Deposition 9
Regional Effects of Nitrogen Emissions
on Health, Visibility & Materials 12
Atmospheric Concentrations 12
Aquatic Concentrations 15
Regional Ecological Effects of Nitrogen Deposition 16
Terrestrial Systems 16
Freshwater Ecosystem Effects 17
Coastal Ecosystem Effects 19
Efforts to Understand and Reduce NOX Emissions 22
Federal and State Regulations 22
Tracking Nitrogen for Accountability: Long Term
Monitoring and Assessment 28
Conclusion 31
Glossary 33
Bibliography 36
Figure References 37
-------
Introduction
^^ ^ itrogen,1 the most abundant element in the air2 we breathe, is essential to plant and
/ ^L / animal life. Historically, this airborne compound has persisted in a state of equilibrium
k ^ as part of a nitrogen cycle embracing air, water, plants, animals, and soils. However,
human inputs from electric power generation, industrial activity, transportation, and agriculture
have disrupted this balance. These sources have released unprecedented quantities of nitrogen
and related compounds to the environment in the past 50 years. Other than nitrogen gas (N^, the
two primary categories into which most nitrogen compounds fall are reduced nitrogen, typically
dominated by ammonia species (e.g., NH3 and NH4+), and oxidized nitrogen, composed primarily
of nitrogen oxides (NO^. Of these two categories of nitrogen compounds, oxidized nitrogen sources
are subject to a variety of regulations that limit emissions. On the other hand, sources of reduced
nitrogen remain largely unregulated. While this document discusses certain sources and issues with
regard to reduced nitrogen, it focuses primarily on atmospheric emissions, deposition, and impacts
of oxidized nitrogen (NOX emissions).
Nitrogen emissions can affect human health in various ways. Nitrogen dioxide (NO^ is irritating
to human lungs, and aids in the formation of particulate »«/fer and o^pne. These airborne byproducts
of nitrogen emissions can cause premature mortality and chronic respiratory illness such as bron-
chitis or asthma, as well as aggravate existing respiratory illness. While less directly linked to atmo-
spheric emissions, nitrate contamination of drinking water supplies, largely from agricultural sources,
can result in methemoglobinemia or Blue Baby Syndrome.
Nitrogen oxides also contribute to a range of environmental effects including the formation of
acid rain, changes in plant and animal life in some ecosystems, and reduced visibility. We have
already seen the impacts that increased nitrogen levels can have across the United States. Certain
forests outside Los Angeles experience reduced growth rates, grasslands in the Midwest suffered a
loss of species diversity, streams in Virginia are too acidic to support trout populations, estuaries
such as Long Island Sound and Chesapeake Bay experience noxious algal blooms, and visibility in
many national parks has diminished to the extent that it is nearly impossible to see some of our
nation's most scenic natural wonders.
1 Throughout the report, terms that are defined in the Glossary at the end of the document,
will be italicized the first time they appear in the report
2 Nitrogen gas (N^ makes up 78 percent of the atmosphere.
-------
Acidification
of Lakes
and Streams
Changes in
Soil Chemistry
Nitrogen
Saturation
of Watersheds
Eutrophication
of Estuaries
and Near
Coastal Waters
Health and
Environmental Effects
of Atmospheric
Nitrogen
Premature
Death from
Particulate Matter
Increased
Ground water
Nitrate
Concentrations
Degradtion of
Materials and
Cultural
Resources
Pulmonary and
Respiratory
Dysfunction and
Disease from
Ozone and
Particulate Matter
Need For a Regional Approach
The U.S. Environmental Protection Agency has a long history of addressing and assessing the
impacts of nitrogen emissions. For example, a series of actions including the implementation of
National Ambient Air Quality Standards (NAAQS) affecting both mobile and stationary sources and
NOX reduction under the Acid Rain Program have achieved significant reductions in NOX emis-
sions. Additional actions scheduled for implementation in future years will further reduce NOX
emissions from stationary and mobile sources. The EPA also undertakes significant efforts to
assess the results of past policies and evaluate the need for future actions to reduce NO emissions.
Such assessment efforts require an understanding of the various sources from which nitrogen
enters the environment; the multiple pathways by which nitrogen moves through the environment;
and the effects on human health, ecosystems, and materials that result from exposure to nitrogen-
related compounds. This document details actions undertaken to reduce NO emissions, as well as
efforts to assess the results of those actions, and briefly describes the need for further NO x emis-
sion reduction efforts (see pages 22-30).
Once nitrogen compounds are released into the environment, they can travel hundreds of miles
from their sources, affecting remote communities and resources downwind. This phenomenon
-------
can be seen in the acidification of lakes and streams in the Adirondack region of New York State
and in other eastern areas. These regions are downwind of the Ohio River Valley and the growing
southeast, the locations of significant portions of the nation's power and metals industries and
areas of increasing vehicle use, all of which represent major sources of emissions. Even when one
state curtails its production of pollutants such as NOX, emissions from other states still travel,
cross state boundaries, and affect downwind regions. In addition, nitrogen pollution can enter
aquatic environments as runoff from terrestrial systems or directly through atmospheric deposition,
connecting atmospheric, terrestrial, freshwater, and estuarine systems. Thus, nitrogen pollution is
truly a regional problem with human health and ecological impacts that not only occur at signifi-
cant distances from the source of the pollution, but in a different environmental medium than the
one into which the pollutant was originally emitted.
Since air pollutants do not recognize political boundaries, states and communities cannot indepen-
dently solve all of their air pollution problems. Resolving air pollution control issues often requires
state and local governments to work together to reduce air emissions. For example, the Clean Air
Act Amendments of 1990 (CAAA) established the Ozone Transport Commission to develop re-
gional strategies to address and control ground level ozone pollution in the northeastern U.S. The
result of that CAAA provision, the Ozone Transport Commission NOX Budget Program, has
demonstrated promising results in reducing emissions with economic efficiency. In the years since
passage of the 1990 CAAA, it has become clear to EPA and states that addressing the impacts
from nitrogen emissions requires regional or national approaches, as state and local actions alone
will be inadequate to solve the problems.
Structure of the Report
The release of nitrogen compounds into the environment is an important, multifaceted issue. This
report is intended to assist an informed general audience in better understanding the many aspects
and implications of nitrogen pollution. The report discusses EPA's current understanding of the
causes of and impacts from excessive nitrogen emissions and deposition. It is organized according
to the main areas of analysis noted above, with sections focused on nitrogen sources; multiple
transport and exposure pathways; regional effects on human health, visibility and materials dam-
ages; regional ecological effects; and continuing efforts to reduce them.
-------
Nitrogen
Sources
^^ ^ itrogen gas is a naturally occurring compound integral to human and other life on the
/ ' k / planet. While representing only a fraction of the total nitrogen found in the envi-
JL ^ ronment, the incremental levels of nitrogen resulting from human activities can have
significant human and ecological health impacts. Since 1970, human activities have doubled the
amount of nitrogen entering terrestrial, aquatic, and marine ecosystems. The most common nitro-
gen-related compounds emitted into the air by human activities are collectively referred to as nitro-
gen oxides, or NOX, which represents primarily nitric oxide (NO)
and nitrogen dioxide (NO^. Both of these compounds are formed
when oxygen gas (O^ and N2 are heated to very high temperatures.
This can occur through both natural and man-made processes.
Natural Sources
Natural events that generate extreme heat, primarily lightning, com-
bine oxygen and nitrogen to form nitrogen oxide. Nitrogen from
the atmosphere is also made available to plants and animals through
a process called biological nitrogen fixation. Certain types of algae and bacteria are able to extract
nitrogen from the air, making it usable by plants and, ultimately, all organisms that eat plants for
nourishment. In the absence of
man-made sources of nitrogen,
most nitrogen pulled from the at-
mosphere by biological nitrogen
fixation is re-emitted to the atmo-
sphere through a process called
denitrification. More importantly,
little of the nitrogen from these
natural sources moves from one
environmental system to another
(e.g., from forests to estuaries).
U.S. Emissions of NOX
(1998, by county)
-------
Man-made Sources
Burning of Fossil Fuels
The combustion of fossil fuels, in engines used
in transportation as well as in electric utility and
industrial boilers, accounts for over 90 percent of
the NOX released in the U.S. due to human activ-
ity. While levels of most pollutants are declining,
concentrations of nitrogen dioxide in the atmo-
sphere have remained basically steady over the past
decade as emissions of NOX have increased by
two percent. Regulatory requirements in the 1990
CAAA have improved the combustion process so
that fewer contaminants are now released per unit
of fuel burned than ever. Despite increasing strin-
gency of combustion controls, increases in power generation and vehicle miles traveled will gradu-
ally offset these improvements. Without further regulatory actions or a cap, emissions are unlikely
to decrease significantly.
Of the major sources of NOX emissions, two categories predominate - large combustion units
(including power generation and other heavy in-
dustry) and transportation-related sources (domi-
nated by cars and trucks, but also including trains,
ships, airplanes, and other non-road vehicles).
Trends in National Emissions
of Nitrogen Oxides, Volatile Organic Compounds,
and Sulfur Dioxide, 1900-1998
^ AA J> ^
« / u \ /-v^ / /\J
= ry w \ / A.-'-1"1^^"'^ /
f~ 77 y^\s^^' /^
1 /^ - /-^
/ j .x-^
NOx
VOC
S02
\J '''N
^"S
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990
Year
From 1988 to 1997, large, stationary utility and
industrial burners accounted for roughly 10.5 to
11 million short tons, or approximately 45 per-
cent, of the NOX entering the U.S. atmosphere
each year from human activities. EPA's Acid Rain
program resulted in a 40 percent reduction in NOX
emission rates from large utility boilers and addi-
tional reductions due to summertime ozone con-
Fuel Consumption and Vehicle-Miles
of Travel
GALLONS PER
VEHICLE
-------
On-Road and
Non-Road Engines
and Vehicles
53%
Fuel Combustion -
Other
5%
Fuel Combustion -
Industrial
12%
1998 National Nitrogen Oxide (NOX) Emissions
by Principal Source Category
Fuel Combustion -
Electric Utility
25%
trols are expected over the next several years.
However, increases in electricity production are
expected to gradually erode the effect of these
measures. In addition to stationary point sources,
transportation-related sources have added between
11 and 12 million tons of NOX to the atmosphere
for each of the past 15 years, contributing 53 per-
cent of all NOX emissions. These emissions are
concentrated in large urban areas and are a major component of urban smog. NOX emissions from
stationary and mobile sources will be reduced by various current and future regulations. These
regulations are discussed further in this report under "Efforts to Understand and Reduce NOX/
Nitrogen" (see p. 22).
Agriculture
Nitrogen compounds added to the terrestrial environment from agricultural sources can also im-
pact water and the atmosphere. In most cases, this nitrogen takes the form of ammonia or ammo-
nium.
Farmers added 22 million tons of nutrients to American crops in 1997, more than half of which
was nitrogen. This process increases crop productivity, especially as intensive cultivation depletes
soil's natural nutrients. It can also cause excess nutri-
ents from these non-point sources to wash into streams,
rivers, and lakes. In addition, this nitrogen can seep or
leach into local groundwater, potentially impacting the
quality of drinking water.
Agricultural Runoff and Leaching
SEEPAGE
GTOUWM/VATER BEEPACe
H9CMKK
TO STREAMS
Commercial feedlots, often containing large numbers
of animals in a small area, also contribute significant
quantities of nitrogen to local water supplies. As many
animals are confined to a location over time, waste builds
up and, if not treated properly, leaches into groundwa-
-------
ter or runs off into streams. In
1997 alone, over a million tons of
nitrogen leached into southeastern
U.S. surface waters from manure,
and surface waters in the south-
central and north-central regions
of the country received similar
loadings.
Nitrogen Input as Fertilizer
July 1996-June 1997
0-150,000
[151,000-300,000
301,000-450,000
451,000-600,000
601,000-750,000
> 751,000
(short tons)
In addition, agricultural operations
can be an important source of atmospheric nitrogen. In 1998, for example, agriculture soil man-
agement accounted for 70 percent of emissions of nitrous oxide (N2O), a powerful greenhouse gas
that contributes to climate change. Evaporation from settling ponds used in treating waste from
large animal feedlot operations can also contribute to airborne transport of nitrogen compounds,
with local as well as broader impacts.
-------
Multiple Transport
and Exposure Pathways
^Transport / Transformatioril [TExposure Pathways)
^. ^Photochemistry
^Chemical Transformations
^Atmospheric
Deposition
irborne nitrogen emissions reach soil and water resources as well as people, buildings,
and other materials through multiple pathways. Ozone generation; production of particul-
^fc J^ ate matter; and wet, cloud, and dry deposition', all contribute to the transport, exposure, and
deposition of airborne nitrogen emissions. Airborne pollutants can travel hundreds of miles,
affecting entire regions rather than just the area immediately surrounding a specific point or mobile
source. In addition, nitrogen
compounds also migrate once
deposited into terrestrial or
aquatic systems. When depos-
ited onto land, for example,
nitrogen compounds often
leach into groundwater or mi-
grate into surface water sys-
tems where they can move
downstream affecting estua-
rine and coastal ecosystems.
The regional, transboundary
nature of mobile air contaminants such as NOX has challenged regulators for years. The geo-
graphic separation between cause and downwind effect has made it difficult to assign responsibility
for specific damages to sources of contamination and reduces the immediate motivation of these
sources to limit NOX emissions. Recent petitions from downwind states in the eastern U.S. im-
pacted by pollution have helped to stimulate action at the regional and national levels.
Human health impacts are associated with both chronic and acute concentrations of pollutants in
the air that people breathe. Most ecological impacts result from the cumulative impacts of long-
term deposition of atmospheric nitrogen onto terrestrial or aquatic systems.
Atmospheric Concentrations
Ozone
NOX emissions can affect people and natural resources through the formation of ozone in the
lower atmosphere. NOX is key to the reaction that forms ozone, effectively producing many mol-
ecules of ozone for each NOX molecule that is emitted. While ozone is a beneficial component of
-------
the upper atmosphere, it is damaging to both ecological and human health when found in the lower
atmosphere. Impacts on trees and plants include impairment of growth and commercial yield,
reduction in the survival of seedlings, increase in susceptibility to disease and foul weather, and
reduction in habitat quality for wildlife. These effects, as well as human health impacts associated
with ozone such as respiratory problems, are discussed in more detail later in the report.
Paniculate Matter
Nitrogen emissions also contribute to the formation of particulate matter. The term particulate
matter (PM) refers to a combination of dust, soot, and solid and liquid masses that form in the
atmosphere. Nitrogen oxides interact with other compounds to form the fine particles and drop-
lets that constitute PM. While PM restricts visibility and contributes to haze problems, these
particles are of greatest concern because of their impact on human health, contributing signifi-
cantly to respiratory damage. Fine particles (defined as having a diameter of 2.5 microns (jam) or
less, known as PM ) are especially damaging as they penetrate deeper into lung tissue. As a result,
EPA promulgated a new NAAQS for PM25 in 1997 and is now monitoring levels of PM25 as well
as of coarse particulate matter (particles with a diameter of up to 10 um, known as PM _) in order
to determine which areas of the country currently experience levels of exposure above these
standards. By 2002, regulators will have sufficient data on PM to determine which areas exceed
these standards. Existing data indicate that ambient concentrations of PM1Q decreased 26 percent
between 1988 and 1997, but 70 counties in the U.S., primarily in western states, still do not meet
PM1Q standards. Another source of information for areas designated as non-attainment is the
Green Book, located at http://www.epa.gov/oar/oaqps/greenbk.
Nitrogen Deposition
Wet Deposition
Wet deposition of sulfur and nitrogen compounds that contribute to acidification of lakes, streams,
and soils is commonly known as acid rain, although such add deposition also takes the form of snow,
sleet, or hail. Certain nitrogen compounds interact with water vapor and droplets in the atmo-
sphere so that the water becomes acidic. Wet deposition is intermittent, since acids only reach the
earth when precipitation falls. Nevertheless, it can be the primary pathway for deposition of
pollutants in areas that receive significant quantities of precipitation. In part because of the im-
portance of climate in combination with emissions distributions, the eastern U.S. receives more
-------
Estimated Annual Wet Deposition: 1985-1999
Ammonium
1985-1989 1995-1999
Estimated Annual Deposition (millimoles/meter2)
3 6 9 12 15 18 21 24 27
acidic precipitation than the rest of the country, with the greatest rates of deposition occurring in
Ohio, West Virginia, western Pennsylvania, upstate New York, and other parts of the northeast.
As the accompanying maps of wet deposition demonstrate, sulfate deposition has decreased in
recent years while deposition of nitrate and ammonium have increased.
Wet deposition contributes to seasonal variation in nitrogen inputs to an ecosystem. When acidic
or nitrogen-contaminated snow falls during the winter, many of the nitrogen compounds remain
stored in the snow until it melts. Particularly in the northeast, large quantities of nitrogen com-
pounds are suddenly released to the ecosystem as snow melts and heavy rains fall in the early
spring. These surges can be especially damaging to fish and other resources, as described on page
18.
Water quality monitoring programs can miss dramatic seasonal variations in nitrogen inputs. The
full toxicity that occurs during seasonal events is missed if samples are collected infrequently or if
measurements of nitrogen levels are averaged over a year. Brief surges in nitrogen inputs such as
those that occur during spring snowmelts and precipitation may reach levels that are four or five
-------
times the average annual concentration, and thus have highly toxic impacts on organisms, some-
times resulting in fish kills. Even when annual data are averaged, overall trends in nitrogen concen-
trations still show an increase over the past 20 years. As levels of sulfate decrease, nitrogen com-
pounds have become increasingly significant as contributors to long-term acidification.
Cloud Deposition
Acidic compounds can reach plants, soil, and water from contact with acidic clouds as well as from
precipitation. While cloud deposition affects only a limited number of locations, it can provide a
relatively steady source of nitrogen compounds and other acids in comparison with wet deposi-
tion. These conditions are most common at high altitudes, where clouds have been shown to
contribute as much as 40 percent of total nitrogen inputs. Because high elevation ecosystems
often have shallow topsoils, they are chemically less able to buffer the impacts of these inputs on
sensitive alpine species. As a result, trees such as the red spruce have declined in areas of signifi-
cant cloud deposition, including much of the southern Appalachian mountains.
Dry Deposition
Dry deposition is similar to the other pathways, but takes place when acidic gases and particles in
the atmosphere are deposited directly onto surfaces when precipitation is not occurring. This
process provides a more constant source of
deposition than the other pathways. Dry
deposition is therefore the primary acid depo-
sition pathway in arid regions in the West.
For example, areas such as the Joshua Tree
National Park suffer significantly from dry
deposition due in part to emissions from Los Angeles and the surrounding areas. The contribution
of dry deposition to total deposition around the country ranges from 20 to 60 percent.
-------
Regional Effects of Nitrogen
Emissions on Health,
Visibility & Materials
Jt irborne nitrogen compounds not only affect human health directly, but also
L^L contribute to the formation of other harmful air pollutants including smog and
tJL* J^ fine particles. Nitrogen oxides can inflict damage on the lungs at relatively low levels of
exposure, and nitrogen emissions and their byproducts can limit visibility and damage buildings
and other structures.
These impacts can be felt far from the geographic origin of the nitrogen. Pollutants can travel
great distances and, when combined with volatile organic compounds in presence of sunlight,
form ozone in areas far removed from their source.
Long-term exposure to NO2 can cause lasting damage to the lungs and can increase susceptibility
to respiratory infections. Young children, asthmatics, and the elderly are particularly sensitive to
these conditions. Dangerous levels of NO in the atmosphere are rare, however, as all areas in the
U.S. currently meet NAAQS for NO2. Accordingly, the most immediate effect on human health
from nitrogen oxide emissions is indirect through the production of particulate matter and
ozone, which affect millions of people every year.
Human Health and Other Non-Ecosystem Effects of
Nitrogen Compounds
premature
death
increasing
emergency
room visits
changes in
lung function
shortness of
breath'
degradation
of metallic
and painted
surfaces
erosion of
monuments
pulmonary
inflammation
increased
susceptibility
to respiratory
disease
blue baby
syndrome
mobilization of
toxic metals
I I
Atmospheric
Concentrations
Particulate Matter
PM of all sizes affects respiratory func-
tion, with smaller particles (diameter
< 2.5 um) especially penetrating deep
into the lungs. Premature mortality,
aggravation of existing respiratory
conditions (indicated by increased hos-
pital admissions and emergency room
visits, as well as lost school and work
days), and changes in lung tissue and
function are all linked to even low am-
bient PM concentrations.
-------
Ozone
Nitrogen emissions can also indi-
rectly affect respiratory function
through the formation of ozone.
While ozone is a naturally occur-
ring and protective component of
the upper atmosphere, its presence
in the lower atmosphere poses
health risks. Formed mostly as a
product of combustion, NOX is
key to the chemical reaction that
Non-attainment Designations for Ozone as of June 2000
: i
lUllipil
forms O . Both gases are important components of smog, are found predominantly in urban areas, and
can travel long distances from their origins. In 1998 alone, an estimated 100 million people lived in non-
attainment areas and therefore experienced exposure to ozone concentrations greater than the levels set by
the NAAQS to protect public health.
Ozone has an especially strong impact on respiratory function when individuals are exercising, irritating
even healthy lungs, decreasing the volume of air a person can take in with each breath, and causing fast,
shallow breathing. Concentrations as low as 80 parts per billion (ppb) can cause damage when people are
exposed for over eight hours at a time, as can levels of 120 ppb over even short periods of time. These
conditions are common in urban areas across the country, especially in summer months when heat and
humidity promote the production of ozone. In addition, ozone increases respiratory and pulmonary sen-
sitivity and inflammation and overall susceptibility
Number of Days with Unhealthy Levels of
Ozone in 1999
20
Houston Cleveland Philadelphia Detroit Fresno
TX OH PA Ml CA
to respiratory disease.
Visibility Impact/ Material Damage
Along with SO2 emissions, nitrogen emissions con-
tribute to an increase in regional haze and a result-
ing decrease in visibility. The same gases and par-
ticles that pose risks to lung tissue as fine particles
also contribute to regional haze and obstruct our
view. Scientists estimate that the natural range of
visibility, absent the effects of pollution, would be
-------
Effects of Haze-Causing Emissions on Visibility
approximately 110 to 115 miles in the
western U.S. and 60 to 80 miles in the
East. Under current conditions, vis-
ibility in the West is between 30 and
90 miles and 15 to 30 miles in the East.
While haze can affect any region of
the country, its impact is felt most sig-
nificantly in certain areas, including
such landmark sites as the Grand Can-
yon, Yellowstone, Mount Rainier,
Shenandoah, Great Smokeys, and Everglades National Parks. EPA is working with other federal
agencies and states to cut emissions of NOX and other haze-causing pollutants in order to improve
visibility at these and other sites. In May 2001, EPA announced a proposed rule to help states take
steps to control haze-causing emissions from older power plants and industrial facilities. The
proposal will affect facilities in 26 industrial categories listed in the Clean Air Act, including coal-
fired utilities, industrial boilers, refineries, and iron and steel plants that were build between 1962
and 1977. Facilities would have to comply with the proposal no later than 2013.
Reducing atmospheric concentrations of nitrogen compounds will also lessen the harmful impacts
of air pollution on buildings and other structures, especially those made of calcite-rich materials
such as marble and limestone. When nitric, sulfurous, and sulfuric acids in polluted air react with
the calcite in marble and limestone, the calcite dissolves. In exposed areas of buildings and statues,
we see roughened surfaces, removal of material, and loss of carved details. Stone surface material
may be lost all over or only
in spots that are more ex-
posed. Acid deposition af-
fects stone monuments
across the U.S., including the
Capitol Building and other
national monuments in
Washington, D.C.
Effects of Air Pollution on Structures
Carvings at the base of columns (above) show that
carved details and sharp edges remain on sheltered
areas. On an exposed portion of the carving (right),
the edges of the marble have rounded and the
surface has roughened.
-------
While not as obvious as the damage done to stone, a wide variety of other materials are damaged
the byproducts of NOX emissions. Ozone chemically attacks elastomers (natural rubber and cer-
tain synthetic polymers), textile fibers and dyes, and to a lesser extent, paints. For example, elas-
tomers become brittle and crack, and dyes fade after exposure to ozone.
Aquatic Concentrations
Nitrate Concentrations in Drinking Water
As described above, respiration of airborne particles and compounds poses significant human
health risks. However, other nitrogen pathways, such as drinking water supplies, also represent
potential sources of risk. Nitrogen exists in ground- and surface waters in the form of nitrate ions
(NO "), whose levels are increasing in many parts of the country. Nitrate found in drinking water
supplies comes from a variety of sources, primarily agricultural. While atmospheric deposition is
not the principal source of nitrate in surface and ground water, increasing numbers of watersheds
across the country are experiencing greater at-
mospheric N impacts, thus raising concern.
The most notable human health impact from
nitrate contamination of water supplies is meth-
emoglobinemia, or Blue Baby Syndrome. This
most frequently affects infants under one year
of age and can cause brain damage or death. A
1990 survey estimated that 4.5 million people a
year were potentially exposed to nitrate levels
above the EPA's Maximum Contaminant Level
(MCL) of 10 mg/L. Nitrate contamination is
not currently generating significant numbers of
documented cases of Blue Baby Syndrome.
In addition, increased levels of nitrate in water
supplies can increase the acidity of the water and
make toxic metals such as mercury more soluble
and therefore more available to fish, some of
which might be consumed by humans.
Nitrate Concentrations in Ground Water
Median concentration of nitrate-in
milligrams per liter. Each circle
represents a ground water study.
Highest (greater than 5.0)
OMedium (0.5 to 5.0)
Lowest (less than 0.5)
Agricultural areas
Nitrate concentrations in agricultural areas
were among the highest measured, but not all
agricultural areas had median values above
the national background concentration.
Urban areas
Nitrate concentrations in urban areas
generally were lower than in agricultural
areas, but 40 percent of urban areas had
median values above the national
background concentration.
-------
Regional Ecological Effects
of Nitrogen Deposition
Once deposited to land and water systems, nitrogen compounds can have
direct long-term effects on the chemistry of soil and surface waters such as lakes
and streams, and can migrate to groundwater and estuarine environments. The move-
ment of the pollutant over hundreds of miles in the atmosphere before being deposited, as well as its
mobility through terrestrial and aquatic ecosystems, illustrates the potential for emissions to affect eco-
logical systems far removed from their sources. These impacts are described in more detail below.
Ecosystem Effects of Nitrogen Deposition
1. change in species composition
2. changes in soil chemistry
3. reduction in forest growth
1. N saturation
2. reduction in water quality
/terrestrial /
ecosystems/ N
/\watersheds\
1. toxicity to fish and other fauna
2. loss of acid neutralizing capacity
Terrestrial Systems
Deposition of nitrogen compounds at lev-
els greater than the biological demand or
need of the affected system can impact for-
est and other terrestrial systems in signifi-
cant ways. Too much nitrogen can lead to a
surplus of nutrients resulting in over-fertili^a-
tion. This can impact species diversity by fa-
voring some nitrogen-tolerant species over
other species that are more sensitive to the
nutrient. In some ecosystems, such as grass-
lands, nitrogen is the limiting factor for
growth. In these systems, other nutrients
are in sufficient supply, and so the amount of available nitrogen dictates what growth can take place.
Plants living in these systems have adapted to low levels of nitrogen and are especially vulnerable to
increased levels of nitrogen deposition. Their decline may lead to changes in the mix of plant species in
an area, causing a decrease in species diversity. New
plants may also move into nitrogen-rich ecosystems,
further challenging native species. Animals that de-
pend on specific plants for habitat and food may
also be threatened by the changes resulting from ni-
trogen inputs.
Excess levels of nitrogen can change the natural cycle
of plant uptake, transformation, and release, rob-
1. eutrophication
2. nuisance algal blooms
3. fish kills
4. habitat loss
Nitrogen-Saturated Forest Ecosystems
in North America
-------
bing soils of their capacity to absorb nitrogen compounds. Known as nitrogen (N) saturation, this phe-
nomenon involves the long-term removal of N limitations on biological activity, accompanied by a
decrease in the ability of ecosystems to retain N inputs. As a result, nitrogen can migrate to surface
waters or leach into groundwater, particularly in sensitive ecosystems with poorly buffered or thin soils
(e.g., mountainous areas in the Colorado Front Range). As more terrestrial ecosystems reach the point
of N saturation, nitrogen inputs reach groundwater and surface water in greater quantities, with effects
that are discussed below.
Acid-Sensitive Forests
C^} Identified as a sensi
ecosystem and sub}
to high deposition rati
Four major forest types asse
When NOX and SO2 emissions enter the
atmosphere, they can be transformed into
acids through complex chemical interac-
tions. These acids return to the earth via
precipitation or when plants come into di-
rect contact with acidic cloud droplets or
gases and airborne particles. Atmospheric
deposition of nitrogen compounds and
other pollutants modifies soil chemistry
and concentrations of important soil nu-
trients. While a majority of acid deposi-
tion in the United States is due to SO2 emissions, NOX emissions are now recognized as an increasingly
important source of the problem.
Extremely high levels of acid deposition, especially from cloud deposition, damage plant leaves and
leach nutrients directly from foliage. Indirect effects of acid deposition are also responsible for damage
to forest ecosystems, as acidic ions in the soil displace calcium and other nutrients from plant roots,
inhibiting growth. Acid deposition can also mobilize toxic amounts of aluminum, increasing its avail-
ability for uptake by plants. Although overall acid deposition rates have declined during the past de-
cades, ecosystems continue to show symptoms of chronic acidification. Moreover, evidence suggests that
acid deposition due to nitrogen rather than sulfur emissions is not declining.
Freshwater Ecosystem Effects
Since growth in freshwater ecosystems is more often limited by phosphorous than by nitrogen, these
systems do not generally suffer from over-fertilization due to nitrogen inputs. However, acidification
due to SO2 and NOX emissions has caused extensive damage in some areas of the country. For ex-
ample, 30 percent of Virginia trout streams are episodically acidic according to one study, and an
-------
Portions of the Neversink River Watershed (New York)
Affected by Chronic and Episodic Acidification
additional 20 percent are at significant risk of
becoming acidic.
Acidification of surface waters results from
both direct deposition of atmospheric acids
onto bodies of water and from deposition of
acids onto soils and plants, with subsequent
leaching out of the watershed. The impact of
acidification on various systems depends on
their chemical properties. Some bodies
of water are better able than others to
neutralize additional inputs of acid, a
characteristic known as add neutralising
capacity (ANC).
Even bodies of water with a high ANC
are often unable to buffer seasonal spikes
in acidic inputs. Many surface waters fall
within a normalpH range during periods
of normal flow but experience episodic
acidification, or short periods of low ANC
and high acidity, during storms or snow-
melt. This temporary change in acidifi-
cation is demonstrated by the situation
in the Neversink, NY watershed. Levels of alu-
minum, which can be toxic to fish, often rise dur-
ing acidification episodes. These events often fall
at biologically sensitive times of the year such as
early spring. Because many species are reproduc-
ing at this time of year, adults and young may both
be unusually sensitive to changes in the water
chemistry, increasing the impacts of nitrogen in-
puts. Addressing episodic acidification requires
year-round rather than seasonal NO emissions
reductions.
Percent ANC <0[ieq/L
| |1% - 5%
| | 5% -10%
| | 10%-20%
>20%
Acid-Sensitive Surface Water
Upper Midwest
jigland
Sensitivity of Some Aquatic Species
to Acid Deposition
Rainbow trout
Brook trout
Falheed minnow
Yellow perch
American toad
Clam
Mayfly
-------
Acidification affects fauna throughout the food chain, resulting in significant direct and indirect dam-
ages to local fish populations. Even when fish are not immediately killed by increases in acidity, impacts
on food sources may force specific species to migrate to less acidic areas. Acidification of surface
waters leads to a decline in species diversity as sensitive species are replaced by species that are more
acid-tolerant.
Coastal Ecosystem Effects
Nitrogen Deposition Airshed
for Chesapeake Bay
Nitrogen is a limiting nutrient for plants and animals in many coastal ecosystems. As a result, increases
in nitrogen and other nutrients frequently increase the rate of supply of organic matter, particularly
algae, to waterbodies such as estuaries. This phenomenon is known as eutrophication, and can lead to a
loss of oxygen in the water, a condition referred to as hypoxia. When excessive quantities of algae grow
in response to extra nutrients, they eventually die and fall to the bottom of the estuary, where they are
decomposed by bacteria. Decomposition consumes oxygen and can deprive an estuary of oxygen
needed for plants, fish, shellfish, and other organisms to live.
While nutrients reach estuaries from a variety of sources, atmospheric deposition is a key pathway as
nitrogen is deposited both directly onto estuarine waters and onto waters and lands in the watersheds
that flow into an estuary. Some of the nitrogen deposited on
the watershed can eventually flush into an estuary; taken to-
gether, atmospherically deposited nitrogen from both direct and
indirect sources can account for as much as 25 percent of all
nitrogen inputs to a large estuary such as the Chesapeake Bay.
The size of the watersheds and especially airsheds which con-
tribute nitrogen to a given estuary are vast in comparison with
the size of the actual water body. An airshed, like a watershed,
is an area in which emissions contribute to the contamination
of a water body. In contrast to watersheds, however, which
define relatively clear boundaries for the flow of surface waters,
there are no clear boundaries to the flow of chemicals in the
atmosphere. The "boundaries" for an airshed do not mean that
emissions from outside the airshed have no impact, nor that
emissions from inside are all of equal impact. The absolute
influence from an emissions source, in terms of likelihood of
deposition on land or water, continuously diminishes as the dis-
tance from the source increases. Thus, an airshed can be de-
-------
Nutrient Effects in Estuaries
Submerged Aquatic Vegetation (SAV) Decline
Thick blooms of algae or
overabundance of macroalgae
prevent sunlight from
penetrating the water column.
Depleted Dissolved Oxygen
Oxygen from wave action
and photosynthesis
mixes with upper fresher
water layer.
Thick blooms of algae or
overabundance of
macroalgae generate too
much organic matter.
Nuisance/Toxic Algal Blooms
Wind blows toxins shoreward,
where they may cause human^.
respiratory problems. <
* Some toxic
blooms cause
fish kills.
Increases occur in the durati
frequency, and spatial extent of
nuisance/toxic blooms.
Epiphytes (a type of
algae) encrust leaf blade, Deeper SAV
dramatically reducing light generally dies
available to the plant. off first as light
is diminished
Consequences
Less habitat is available for fish and shellfish.
Impacts on commercial and recreational fisheries.
Impacts to tourism.
Bacteria use oxygen
decompose algal material.
^
Immobile
Consequences
Less habitat is available for fish and shellfish.
Lower commercial and recreational fish yields.
Impacts to tourism.
Shellfish
become
contaminated
with algal
toxins.
Consequences
Human health endangered by exposure to toxins.
Closure of shellfish beds to harvest.
Impacts on commercial and recreational fisheries.
Impacts to tourism.
fined as the geographic area that encompasses emissions that are most important to the deposition across the
watershed and account for the major percentage (usually around 75 percent) of that deposition.
The most commonly cited impacts of eutrophication are declines in commercial and recreational fisheries and
shellfisheries, resulting largely from damage to sea grass and other habitats. These impacts are felt in the economy
both directly due to the lost catches and indirectly through decreases in tourism in areas where fishing and shellfishing
are impaired. In addition, increases in algal populations, referred to as algal blooms, can result in large floating mats
of algae with impacts on swimming and boating. When this mass of algae begins to decompose, it often produces
noxious smells with expected impacts on the recreational and aesthetic values of the waterways.
Increased quantities of nutrients may also be connected with an increase in the growth of toxic algal blooms. These
blooms, often referred to as brown or red tides, can make water unsafe for swimming and can contaminate fish and
shellfish harvested from the area. While links between nutrients and hazardous algal blooms continue to be re-
searched and confirmed, incidence of the blooms is increasing and spreading to previously unaffected areas. As the
population in coastal areas surrounding estuaries is expected to increase 13 percent in the next 20 years, additional
strain will be added to already struggling estuarine ecosystems.
The National Oceanic and Atmospheric Administration (NOAA) recently released the results of an exhaustive
seven year assessment of eutrophication in 138 estuaries. The assessment found that 65 percent of the major
estuaries in the U.S. experience moderately to highly eutrophic conditions. These conditions are expected to deterio-
rate over the next 20 years in 86 of the estuaries studied, mostly located in the Pacific and Gulf of Mexico regions.
It is important to note that many estuaries in the Pacific region currently exhibit only low to moderate eutrophic
conditions, in contrast to many Atlantic and Gulf Coast estuaries. The projected deterioration is expected as a result
of increasing coastal population density, combined with nitrogen inputs from agriculture, wastewater treatment,
urban runoff, and atmospheric deposition. Taken together, these nitrogen inputs will place additional future strain
-------
-------
Efforts to Understand
and Reduce NO Emissions
x
Federal and State Regulations
EPA and the states are using a number of regulatory programs and activities to address
an important component of total nitrogen pollution - emissions of NOX from both sta-
tionary and mobile sources. These efforts include programs to reduce NOX emissions from new
stationary sources; a program under Title IV of the Clean Air Act (CAA) to reduce NOX from
existing coal-fired power plants; regional approaches such
as the Ozone Transport Commission's (OTC) trading
program; the NOX SIP Call; state petitions under Sec-
tion 126 of the CAA; state programs implementing the
NAAQS; and emissions standards for new mobile
sources. Additionally, future efforts to meet the PM stan-
dards and address regional haze will result in reductions
Projected Total Utility NOX Emissions
Reductions Under Title IV
Without Acid Rain Program 8-1
6.7
8.8
With Acid Rain Program
With NOx SIP Call
4.42
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
-Without Title IV
-With Title IV -*-With NOx Sip Call
of NOX emissions and ambient nitrate concentrations.
New Stationary Sources
New Source Performance Standards
New source performance standards (NSPS) require
emission reductions in both attainment and non-attainment areas. Section 111 of the CAA re-
quires EPA to identify "source categories" emitting criteria air pollutants (e.g., PM) or precursors
of criteria pollutants (e.g., NOX and VOCs) and to establish emissions limits for new, modified, and
reconstructed stationary sources of emissions. To date, EPA has promulgated approximately 100
NSPS, of which approximately ten directly control NOX emissions.
In September 1998, EPA finalized an NSPS for fossil fuel-fired utility and industrial boilers. These
final revised NOX emission limits will reduce the projected growth in NOX emissions from new
sources by approximately 42 percent from levels allowed under current standards.
New Source Review and RACT
Under the CAA, States must apply similar requirements to major stationary sources for NOX emis-
sions as are applied to major stationary sources of VOCs, because both are precursors to ozone.
These provisions require (1) existing major stationary sources to apply reasonably available control
technology (RACT) in certain ozone nonattainment areas and the OTC states, (2) new or modified
-------
major stationary sources to offset increased emissions and to install controls representing the
lowest achievable emission rate (LAER) in ozone nonattainment areas and the OTC states, and (3)
new or modified major stationary sources to install the best available control technology (BACT) in
ozone attainment areas.
Title IV
Title IV of the CAA specifies a two-part strategy to reduce NOX emissions from coal-fired electric
power plants. The first stage of the program, promulgated on April 13,1995, reduced annual NOX
emissions in the United States by over 400,000 tons per year between 1996 and 1999 from two
common types of boilers affected by Phase I of the Title IV SO2 control program (Phase I). In the
second stage of the Title IV Program, EPA established more stringent standards for those boiler
types and established limitations for other types of coal-fired boilers. The Phase II NOX rule will
achieve an additional 1.7 million ton reduction of annual NOX emissions (for a total of over two
million tons), but this regulation does not include a cap on total NOX emissions.
Under Title IV, EPA may only limit the quantity of NOX released per unit of heat input and may
not limit the total number of tons of NOX released over the course of a year. Although emissions
will be reduced significantly by this program, emissions are permitted to rise as more coal is used to
generate more electricity. As a result, concern remains that without a cap on total emissions,
continued increases in demand for electricity and transportation will offset some of the benefits of
ongoing nitrogen reductions. Several states are considering year-round NOX control programs
with emissions caps, but until these programs encompass broader regions, emissions will continue
to cross boundaries and cause damage.
OTC NOX Budget Program
The OTC is comprised of the states of Maine, New Hampshire, Vermont, Massachusetts, Con-
necticut, Rhode Island, New York, New Jersey, Pennsylvania, Maryland, Delaware, the District of
Columbia, and the northern counties of Virginia. In September 1994, the OTC members, with the
exception of Virginia, adopted a memorandum of understanding (MOU) to achieve regional emis-
sion reductions of NOX. In signing the MOU, states committed to develop and adopt regulations
that would reduce region-wide NOX emissions in 1999 and further reduce emissions in 2003. The
OTC NOX Budget Program represents the Northeast's principal mechanism to control NOX emis-
sions in order to make progress towards attainment of the ozone health standard.
-------
The Emissions Cap and Trade Concept
Unitl Unit 2
No Controls
With no controls in place, Unit 1 and Unit 2 each emit
20,000 tons a year.
10,000
Unit 1 Unit 2
The Cap
Each facility must choose an emission reduction
strategy to meet its cap of 10,000 tons. Thus, each
unit must achieve a 10,000 ton reduction from the
20,000 ton emissions level shown above.
5,000
Unitl Unit 2
Emissions Trading
Unit 1 can efficiently reduce 15,000 tons of emissions,
but Unit 2 can only efficiently reduce 5,000 tons.
Since Unit 1 can achieve greater reduction at less
cost, it can hold on to the excess allowances or sell
them to Unit 2. Through this exchange, the same
amount of emissions reductions are achieved, but in
the most efficient manner possible.
The OTC NOX Budget Program involves an emissions cap (or bud-
get) and an allowance trading system which harnesses free market
forces to reduce pollution, similar to the U.S. EPA's Acid Rain Pro-
gram for SO2 emissions. Under this program, affected sources in-
clude all electric power plants with generators greater than 15 MWe
and all industrial boilers with steam generating capacity greater than
250 mm Btu/hour. Sources are allocated allowances by their state
governments. Each allowance permits a source to emit one ton of
NOX during the control period (May through September) for which
it is allocated or during any later control period. For each ton of
NOX discharged in a given control period, one allowance is retired
and can no longer be used.
In the summer of 1999, eight of the OTC States participated in the
trading program. There were 912 affected sources which collec-
tively emitted 174,843 tons of NOX, 20 percent less than the maxi-
mum allowable level of emissions and more than 50 percent below
their emissions in 1990.
NOX SIP Call
In October 1998 EPA completed a rulemaking calling upon 22 east-
ern states and the District of Columbia to submit revised State
Implementation Plans (SIPs) that provide for additional reductions
in NOX emissions. This rule is commonly called the NOX SIP call.
Although some of the affected states challenged EPA's authority to
require these reductions, the DC Circuit Court of Appeals upheld
the requirement for 19 states and parts of two others. Revised SIP
submissions covering approximately 90 percent of the initial NOX
SIP Call emission reductions were due in October 2000, and should
result in a reduction of almost 900,000 tons in NOX emissions in
2007.
Among other provisions, the NOX SIP rule assigns a cap, or "budget," on summertime NOX
emission to each of the affected states. States were required to submit plans to meet about 90
percent of these budgets by October 2000; they must have the mitigating technology in place by
-------
2004; and they must have actual emissions at or below the set levels
by 2007. EPA does not specify how a state must meet its require-
ments, but studies show that tightening NOX controls at electric
generating units and other large industrial sources would be an effi-
cient first step.
With this in mind, EPA developed a model NOX emissions trading
program that states can choose to implement as part of their SIPs.
Under the trading program, a state will assign each major source a
number of allowances for the amount of NOX it may emit (one
allowance permits the release of one ton of NO ). These allow-
ances can be bought, sold, or saved for future use. If a facility emits
more NOX than the quantity for which it has allowances, then it
must either purchase additional allowances or be considered out of
compliance. Units that are out of compliance are subject to a de-
duction of three allowances for each ton they emit above the num-
ber of allowances they hold at the end of the year and may face
additional penalties for noncompliance. This enhances economic
efficiency, as those facilities that can most easily reduce emissions
beyond allowable levels can sell extra allowances to those for which
such changes would pose a greater financial burden. Regardless of
how many allowances a facility holds, however, it may not emit at
levels that would violate any other state or federal limits. This emissions trading program is similar
to the trading program for SO2 conducted by EPA's Acid Rain Program. In the first phase of the
SO cap and trade program, emissions dropped by 30 percent below the allowable level and costs
are now estimated to be approximately 75% less than the amount first predicted by EPA.
Since warm summer temperatures foster the production of ozone, the summertime caps on NOX
can provide significant benefits, especially with respect to ozone levels. However, these reductions
will have limited impact on winter and spring NOX emissions and, therefore, do little to cut depo-
sition loads that affect ecosystems during biologically sensitive times of the year.
Section 126 of CAA
In 1997, eight northeastern states petitioned EPA under Section 126 of the CAA, seeking to re-
duce the transport of NOX from upwind states. In January 2000 EPA took final action on the
Potential Impact of Emissions
Trading Programs on Future Ozone
Conditions: 2007
With Implementation of Clean Air Act Alone
160
1145
115
85
55
40
ppm
With Implementation of Additional Controls
Including an Emissions Trading Program
.160
1145
115
85
55
40
ppm
-------
Regulation
New Stationary
Sources
New Source
Performance
Standard (NSPS)
New Source
Review (NSR)
Recent Regulations Affecting N0x
Compliance Date Affected Sources
Emissions
Projected NOX
Emission Reductions (year
by which reductions
will be achieved)
Major new and reconstructed sources 45,650 tons/year
All major new and modified (2003)
stationary sources apply NOX Best
Achievable Control Technology
(BACT) or Lowest Achievable
Emission Rate (LAER)
Inclusion of
Emission Cap
in Regulation
No Cap
Tide IV Acid
Rain NOX
Group 1 (Phase I): January 1, 1996 Group 1: Coal-fired dry bottom
wall-fired boilers, tangentially fired
boilers
2.06 million tons/yr
(2000)
No Cap
Group 1 (Phase II) and Group 2:
January 1, 2000
Group 2: wet bottom boilers,
cyclones, cell burner boilers, and
vertically-fired boilers (nationwide)
Ozone Transport
Commission
Memorandum of
Understanding
Phase I (NOX RACTsee above):
May 31, 1995
Phase II: May 1, 1999
Phase III: May 1, 2003
Fossil fuel-fired boilers and indirect
heat exchangers with a maximum
rated heat input capacity of 250
mmBtu/hour or more (applies to
northeast Ozone Transport Region,
including Washington, DC and the 11
northeastern States)
320,000 tons/yr
(2003)
Cap
Section 126
May 1, 2003
510,000 tons per ozone season Cap
(2007)
NOX SIP Call
State NOX Budget Programs (and
NO reductions) must be
implemented by May 31, 2004;
budgets to be achieved by 2007
19 States and the District of
Columbia (DC)
880,000 tons per ozone season Cap
(2007)
Mobil Source
Regulations
Tier I Tailpipe standards: 1996
Tier II Gasoline Sulfur Program:
2004 for gasoline sulfur content
nationwide; 2004-2009 for tighter
NOX standards for vehicles
National Low Emission Vehicle
(NLEV) Standards: 1999 in NE
ozone transport region; 2001
nationwide
Tier I Tailpipe standards: light duty
vehicles and trucks
Gasoline nationwide, and cars, light
trucks, and SUVs up to 10,000
pounds gross weight sold outside
California
National Low Emission Vehicle
(NLEV) Standards: light-duty
vehicles and light light-duty trucks
935,000 tons/yr
(2010)
4.454 million tons/yr
(2030)
199,100 tons/yr
(2007)
No Cap
Heavy-duty highway diesel
standards: 2004
Heavy-duty non-road diesel
standards: 1999-2006
Heavy-duty highway diesel standards:
heavy-duty highway diesel engines
Heavy-duty non-road diesel
standards: heavy-duty diesel
construction, agricultural, industrial
engines
Small spark-ignition engine standards,
Small spark-ignition engine small spark-fired engines
standards, phase I: 1997
Small spark-ignition, non-handheld
Small spark-ignition, non-handheld engine standards
engine standards, phase II: 2001-
2007
Locomotive engine standards: new
Locomotive engine standards: 2000 and rebuilt locomotive engines
1.1 million tons/yr
(2020)
1.2 million tons/yr
(2010)
9,900 tons/yr
(2020)
493,900 tons/yr
(2010)
1 Reductions under the Section 126 action are required to begin on May 1, 2003. States may chose to regulate some or all of the same sources that EPA is regulating under the Section 126 action under the NOx SIP Call starting in
2004. For 2004 and beyond, therefore, emissions reductions from the SIP Call action and the Section 126 action should not be considered additive.
2 As originally finalized, the NO^ SIP Call covered 22 States and the District of Columbia and required 1.1 million tons of NC^ reductions. Based on a March 3, 2000 DC Circuit Court Decision, the geographic scope of the SIP
Call and the overall reductions required were slightly reduced. Some additional reductions could be required depending upon finalization of rules to address issues remanded to EPA.
-------
Section 126 petitions requiring sources in 12 states and the District of Columbia to reduce their
NOX emissions during the summer beginning in 2003. In addition to sources in the OTC states,
this action would affect large electric generating facilities and industrial boilers in Ohio, West Vir-
ginia, and Virginia, as well as portions of Michigan, Indiana, and Kentucky.
NAAQS
EPA sets limits for the ambient concentrations of certain pollutants using its authority under the
CAA. These limits are designed to protect public health and welfare throughout the United States
and are referred to as NAAQS. These standards apply to the criteria pollutants: Sulfur Dioxide,
Nitrogen Dioxide, Ozone, Particulate Matter, Carbon Monoxide, and Lead. EPA and the states
share authority for controlling emissions from stationary and mobile sources. EPA sets the NAAQS
and then asks states to submit SIPs which consist of the rules and legislation that the state has
passed in order to meet the standards. If a state fails to submit a plan that attains and maintains
these standards, EPA is required to develop and implement a federal implementation plan (FIP).
While emissions of five of the six criteria air pollutants are down since 1970, emissions of NOX
have risen by 17 percent over this same time period. The rate of increase has slowed dramatically
in recent years because of federal and state actions, and there was only a net increase of two
percent over the last decade.
Mobile Source Emission Limits
Over the last three decades EPA has set increasingly stringent tailpipe standards for automobiles,
trucks, and buses. The effect of those actions has been to reduce significantly the rate of NOX
emissions from new cars compared to those without controls.
In December 1999, EPA announced new limits for tailpipe emissions of NOX. In the next 10
years, these "Tier II" standards will require a 77 percent reduction in emissions from cars and as
much as a 95 percent drop in emissions from sport utility vehicles and light trucks. EPA projects
that virtually the entire national fleet of cars will be replaced by these cleaner-burning Tier II
vehicles by 2030, at which time the benefits of the resulting cleaner air will translate into the
prevention of 4,300 premature deaths, 173,000 cases of respiratory illness, and 260,000 childhood
asthma attacks each year. In addition to these improvements in emissions from gasoline-burning
-------
cars, EPA has promulgated similarly tough standards for diesel trucks. With these standards final-
ized, EPA also plans to address non-road vehicles such as farm and construction equipment.
In addition to the regulation of NOX under the Clean Air Act, the Clean Water Act and the Safe
Drinking Water Act address releases of nitrogen to surface and groundwater. The 1998 Clean
Water Action Plan requires EPA to conduct research and develop assessments of the scope and
impact of nitrogen deposition on all waters. It also asks EPA to work with its partners to use both
Clean Air Act and Clean Water Act authorities to reduce atmospheric deposition of nitrogen that
harms aquatic ecosystems. Actions under these statutes include developing and submitting several
Reports to Congress that outline the effects of nitrogen deposition and the effects of current or
possible future control strategies; working with USDA to make sure atmospheric deposition issues
are addressed in the Concentrated Animal Feeding Operations strategy; and supporting modeling,
monitoring, and specific research projects related to atmospheric deposition of nitrogen and its
effects.
Tracking Nitrogen for Accountability:
Long Term Monitoring and Assessment
In order to evaluate the effectiveness of environmental policies and programs, a firm commitment
to long-term monitoring programs is critical. These programs help in evaluating the status and
trends of visibility, the health of ecosystems, and other important assessment endpoints. For
example, monitoring data allow the Agency to evaluate the effectiveness of emission controls,
explore dose-response relationships, and understand ecological processes. Effective assessment
of environmental policies and programs requires a full suite of monitoring capabilities, including
tracking stack emissions, analyzing atmospheric concentrations of pollutants, measuring wet and
dry deposition on land and water surfaces, and evaluating the ultimate environmental impacts
through surface water chemistry and biological monitoring.
Continuous emissions monitoring (CEM) is the ongoing measurement of pollutants emitted into
the atmosphere in exhaust gases from combustion or industrial processes. While traditional emis-
sions limitation programs have required facilities to meet specific emissions rates, compliance un-
der the Acid Rain Program requires an accounting of each ton of emissions from each regulated
unit. EPA has established requirements for the continuous monitoring of NOX and SO2 for units
-------
Regional Acidification Trends
LTM Lakes in the Northeast
regulated under the Acid Rain Program. Thus, CEM is instrumental in ensuring that the mandated
reductions of NOX and SO2 under the Acid Rain Program are achieved.
Scientists have been monitoring precipitation chemistry for over 20 years. The National Atmo-
spheric Deposition Program (NADP) is a coop-
erative effort established in the late 1970s between
federal and state agencies, universities, electric utili-
ties, and other industries to investigate geographi-
cal patterns and trends in precipitation chemistry
in the U.S. Its network of monitoring sites known
as the National Trends Network (NTN) moni-
tors wet deposition through weekly collection of
precipitation samples across the country. Simi-
larly, the Clean Air Status and Trends Network
(CASTNet) has monitored dry deposition of sul-
fur and nitrogen compounds since 1987. Mea-
surement of dry deposition is complex, and so
CASTNet measures ambient concentrations of
contaminants along with meteorological condi-
tions and then estimates the quantity deposited.
The Temporally Integrated Monitoring of Eco-
systems and Long-Term Monitoring (TIME/
LTM) networks serve a similar purpose for moni-
toring the impacts of acid deposition on surface
waters. Concentrated in the Mid-Atlantic and
Northeast, the TIME/LTM networks monitor
both chronic and episodic acidification. The
TIME network survey sites are sampled annually
in order to determine changes in chronic acidifi-
cation at a regional scale. Complementing these
-1.5
-1.0 -0.5 0.0
Slope of Trend (90% C.I.)
*p<0.05;**p<0.01;***p<0.001
0.5
1.0
Base Cations -
Adirondack:
Vermont
-B ' Mane
-2.0 -1.5 -1.0 -0.5 0.0
Slope of Trend (90% C.I.)
0.5
1.0
Analysis of Northeast regional trends in surface water chemistry
between 1982 and 1994 (Adirondack Mountains, New England)
shows that sulphate concentrations decreased, with stronger
downward trends evident in the 1990s than in the 1980s.
Regional declines in nitrate concentrations were rare and smaller
in magnitude. Recovery in alkalinity (as measured by Acid
Neutralizing Capacity) was observed in the New England region
in the 1990s, but not in the Adirondacks.
-------
sites, the LTM network monitors lakes and streams that are highly sensitive to acidic inputs. These
bodies of water are sampled eight to 16 times per year in order to track episodic acidification and
its connection with chronic acidification. Over 200 lakes and streams have been sampled under
this program for the past six to nine years, providing researchers with the first body of empirical
data with which to understand the relationship between acid deposition and episodic and chronic
acidification, as well as to characterize ecological responses to changes in deposition loadings.
Other monitoring networks administered by government agencies across the country also collect
data on nitrogen deposition and acidification. The National Park Service's (NPS's) IMPROVE
program monitors visibility and the contaminants that affect it; the National Oceanic and Atmo-
spheric Administration's AIRMoN program supports both the NADP precipitation chemistry and
dry deposition networks; and the interagency (EPA and NPS) PRIMENet conducts intensive,
long-term, multimedia monitoring of air, water quality, soil, and sediment quality stressors. The
hundreds of monitoring sites that make up all of these networks provide the data on which scien-
tists base estimates of damage and regulators evaluate and base decisions on emissions limits.
Monitoring over extended time periods and geographic areas is crucial to understand the effective-
ness of environmental policy. Observation data for one month or one year may be misleading if
taken out of the context of larger patterns of deposition, and conditions vary widely both within
and across regions. Many of these monitoring sites have been functioning for over 20 years,
providing a solid basis for judgement.
-------
Conclusion
A Regional Problem
Nitrogen, and more specifically nitrogen oxides (NOX), is indeed a complex and pervasive pollut-
ant. Once emitted into the environment, it travels long distances through atmospheric, terrestrial,
and aquatic systems. Accordingly, it causes direct and indirect impacts on human health and the
environment, often hundreds or thousands of miles away from
its source. Typically, public health and environmental prob-
lems become more regional in nature when it becomes appar-
ent that multiple sources in multiple states contribute to the
problem.
Nitrogen emissions can be linked to almost all the major envi-
ronmental and health threats that the Clean Air Act addresses.
Nitrogen combines with other compounds in the atmosphere
to produce ozone and small particles, both of which cause se-
rious respiratory problems, particularly affecting young chil-
dren, asthmatics, and the elderly. Ozone can also reduce the
resistance of important food crops to disease and pests. Par-
ticulate matter derived from nitrogen is a significant contribu-
tor to regional haze, affecting visibility especially in the west-
ern United States and in urban areas.
Excessive deposition of airborne nitrogen causes a range of
environmental problems including the acidification of surface
waters, groundwater, and soils; forest decline; loss of
biodiversity; changes in the viability of flora and fauna; and
eutrophication of coastal waters. While the most significant human health risks are currently
posed by respiration of airborne particles and compounds, nitrogen exists in groundwater and
surface waters in the form of nitrate ions, whose levels are increasing in many parts of the country.
What Still Needs to Be Done to Address the Problem?
EPA, along with other federal and state agencies, is engaged in a comprehensive monitoring and
assessment program to better understand the effectiveness of current emission control programs
Principal Oxidized Nitrogen Airshed
for Hudson/Raritan Bay, Chesapeake
Bay, Pamlico Sound, and Altahama
Sound
-------
on the atmospheric concentrations of pollutants, deposition on land and water surfaces, and the
ultimate environmental and human health impacts. For example, uncertainties remain regarding
the possible links between nitrates and drinking water concerns.
A series of actions including the implementation of NAAQS affecting both mobile and stationary
sources and NOX reductions under the Acid Rain Program have achieved significant reductions in
NOX emissions. Nevertheless, additional reductions are needed to fully attain the ozone and fine
particles NAAQS, address remaining environmental concerns (e.g., acid rain), and deal with emerg-
ing problems (e.g., coastal eutrophication).
While emissions of sulfur dioxide declined from 1990 through 1999, emissions of NOX increased
slightly. Although combustion processes are expected to become more efficient, without the imple-
mentation of an emissions cap, increases in the demand for electricity and vehicle travel will erode
this progress. In addition, even though EPA has made significant progress in reducing summer
NOX emissions when human health impacts from ozone are greatest, more needs to be done on a
year-round basis, especially to protect ecological systems. Many ecological impacts, including the
damage to fish reproductive success, are at their greatest during the spring when snowmelt contrib-
utes to large increases in the acidification of lakes, rivers, and estuaries.
While much has been done, EPA remains committed to identifying, analyzing, and implementing
cost-effective solutions to the complex regional consequences of nitrogen pollution.
-------
Glossary
Acid deposition complex chemical and atmospheric phenomenon that occurs when emissions
of sulfur and nitrogen compounds and other substances are transformed by chemical processes in
the atmosphere, often far from the original sources, and then deposited on earth in either wet or
dry form. The wet forms, popularly called "acid rain," can fall to earth as rain, snow, or fog. The
dry forms are acidic gases or particulates.
Acid neutralizing capacity (ANC) measure of ability of water or soil to neutralize acidic
inputs and resist changes in pH.
Airshed area from which approximately 75 percent of the airborne emissions contributing to the
contamination of a water body originate.
Atmospheric deposition the process by which gases and particles in the atmosphere are depos-
ited on terrestrial and aquatic surfaces.
Biological nitrogen fixation process by which certain types of algae and bacteria pull nitrogen
from the air, making it available for uptake by vegetation.
Chronic acidification condition when an ecosystem exhibits symptoms of acidification over an
extended period of time, rather than during temporary episodes.
Clean Air Act Amendments (CAAA) federal legislation passed in 1990 enacting broad mea-
sures by which to improve air quality in the United States.
Cloud deposition pathway in which acidic droplets in the atmosphere are deposited onto sur-
faces through direct contact.
Denitrification process through which nitrate is transformed and re-emitted to the atmosphere
as N2O or N2, forms of nitrogen which are not usable by plants and animals.
Dry deposition process by which acidic compounds in the atmosphere are deposited directly
onto surfaces in the absence of rain, snow, fog, or sleet.
-------
Episodic acidification temporary spikes in the acidity of a body of water due to surges in acidic
inputs. These surges are most often associated with seasonal events such as snowmelt that can
release quantities of stored nitrate ions.
Estuary region of interaction between rivers and near-shore ocean waters, where tidal action and
river flow mix fresh and salt water. Such areas include bays, mouths of rivers, and lagoons.
Eutrophication An increase in the rate of supply of nutrients to a coastal ecosystem that leads
to excessive algae growth, oxygen depletion, and resulting impacts on species and ecosystems.
Hypoxia Condition in which the concentration of dissolved oxygen in water is less than the
minimum required for most marine life to survive and reproduce.
Leaching process by which soluble constituents are dissolved and filtered through the soil by a
percolating fluid.
Methemoglobinemia medical condition in which nitrates and nitrites in drinking water impair
the ability of hemoglobin in the blood stream to transport oxygen (also known as Blue Baby
Syndrome).
National Ambient Air Quality Standards (NAAQS) - standards established by EPA that apply
to outdoor air throughout the country in order to protect public health.
Nitrate compound containing one nitrogen atom and three oxygen atoms (NO ~) that can exist
in the atmosphere or as a dissolved gas in water and which can have harmful effects on humans and
animals. Nitrates in water can cause severe illness in infants and domestic animals.
Nitrogen nonmetallic element that constitutes 78 percent of the air by volume, occurring as a
colorless, odorless, almost inert diatomic gas, N2, in various minerals and in all proteins.
Nitrogen cycle series of processes in which nitrogen moves from the atmosphere to plants,
soils, and waterbodies, and back to the atmosphere.
Nitrogen oxide (NOx) the result of photochemical reactions of nitric oxide in ambient air;
major component of photochemical smog; product of combustion from transportation and sta-
tionary sources and a major contributor to the formation of ozone in the troposphere and to acid
deposition.
-------
Nitrogen saturation a condition in forested ecosystems in which nitrogen impacts have led to
long-term removal of N limitations on biotic activity, accompanied by a decrease in the capacity of
an ecosystem to retain nitrogen.
Non-attainment area area that does not meet one or more of the National Ambient Air Quality
Standards for the criteria pollutants designated in the Clean Air Act.
Non-point source diffuse pollution sources (i.e., without a single point of origin or not intro-
duced into a receiving stream from a specific outlet). The pollutants are generally carried off the
land by storm water. Common non-point sources are some agricultural, forestry, and mining
practices; construction sites; dams; land disposal (e.g., landfills); saltwater intrusion; and urban
runoff.
Over-fertilization occurs when an ecosystem receives excess quantities of nitrogen or other
fertilizing nutrients, and may result in a loss of species diversity.
Ozone (O3) gaseous allotrope of oxygen, formed naturally from diatomic oxygen by electric
discharge or exposure to ultraviolet radiation. Its presence in the stratosphere protects the Earth
from ultraviolet radiation, while its presence in the lower troposphere is damaging to plant, animal,
and human health.
Particulate matter (PM) fine liquid or solid particles such as dust, smoke, mist, fumes, or smog,
found in air or emissions.
pH an expression of the intensity of the basic or acid condition of a liquid; may range from 0 to
14, where 0 is the most acid and 7 is neutral. Natural waters usually have a pH between 6.5 and 8.5.
Smog air contamination caused by chemical reactions of pollutants formed primarily by the
action of sunlight on oxides of nitrogen and hydrocarbons.
Watershed land area that drains into a stream; the watershed for a major river may encompass a
number of smaller watersheds.
Wet deposition commonly known as acid rain, although it can also take the form of snow, sleet,
or hail; atmospheric deposition that occurs when precipitation carries gases and particles to the
Earth's surface.
-------
Bibliography
Bricker, Suzanne B., et al. 1999. National Estuarine Eutrophication Assessment: Effects of Nu
Enrichment in the Nation's Estuaries, National Oceanic and Atmospheric Administration: Silver Springs,
MD.
Church, M. Robbins and John Van Sickle. 1999. "Potential Relative Future Effects of Sulfur and
Nitrogen Deposition on Lake Chemistry in the Adirondack Mountains, United States." Water
Resources Research 35 (7): 2199-2211.
Driscoll, C. T., et al. 2001. "Acidic Deposition in the Northeastern US: Sources and Inputs,
Ecosystem Effects, and Management Strategies." Bioscience, in press.
Fenn, Mark E. and Mark A. Poth. 1999. "Temporal and Spatial Trends in Streamwater Nitrate
Concentrations in the San Bernardino Mountains, Southern California." Journal of Environmental
Quality 28: 822-836.
Fenn, Mark E., et al. 1998. "Nitrogen Excess in North American Ecosystems: Predisposing
Factors, Ecosystem Responses, and Management Strategies." Ecological Applications % (3): 706-733.
General Accounting Office. 2000. AcidRain: Emissions Trends and Effects in the Eastern United States,
GAO: Washington, DC.
National Acid Precipitation Assessment Program. 1990. 1990 Integrated Assessment Report, NAPAP:
Washington, DC.
National Acid Precipitation Assessment Program. 1998. NAPAP Biennial Report to Congress: An
Integrated Assessment, NAPAP: Washington, DC.
National Atmospheric Deposition Program. 1999. Nitrogen in the Nation's Rain, NADP: Champaign,
Illinois.
National Research Council. 2000. Clean Coastal Waters: Understanding and Reducing the Effects of
Nutrient Pollution, National Academy Press: Washington, DC.
Stoddard, J. L., et al. 1999. "Regional Trends in Aquatic Recovery from Acidification in North
America and Europe." Nature 401: 575-578.
United States Environmental Protection Agency. 2000. Eatest Findings on National Air Quality:
1999 Status and Trends, Office of Air Quality Planning and Standards: Research Triangle Park, NC.
United States Environmental Protection Agency. 2000. National Air Pollutant Emission Trends,
1900-1998, Office of Air Quality Planning and Standards: Research Triangle Park, NC.
United States Environmental Protection Agency. 2000. National Air Quality and Emissions Trends
Report, 1998, Office of Air Quality Planning and Standards: Research Triangle Park, NC.
Van Sickle,}., et al. 1997. "Estimation of Episodic Stream Acidification Based on Monthly or
Annual Sampling." Journal of the American Water Resources Association 33 (2): 359-366.
-------
Figure References By
Report Section
Nitrogen Sources
p. 4 United States Environmental Protection Agency. 2000. National Air Pollutant Emission Trends, 1900-1998, Office of
Air Quality Planning and Standards: Research Triangle Park, NC.
p. 5 United States Environmental Protection Agency. 2000. National Air Pollutant Emission Trends, 1900-1998, Office of
Air Quality Planning and Standards: Research Triangle Park, NC.
p. 5 United States Department of Transportation. Highway Statistics 1999, Federal Highway Administration: Washington,
B.C.
p. 6 United States Environmental Protection Agency. 2000. National Air Pollutant Emission Trends, 1900-1998, Office of
Air Quality Planning and Standards: Research Triangle Park, NC.
p. 6 Adapted from: United States Geological Survey. 1999. The Quality of Our Nation's WatersNutrients and Pesticides,
United States Geological Survey Circular 1225, 82 p.
p. 7 The Fertilizer Institute. Statistics: U.S. Fertiliser Use. www.tfi.org. Accessed 17 February 2000.
Multiple Transport and Exposure Pathways
p. 8 Adapted from: National Science and Technology Council. 1999. The Role of Monitoring Networks in the Management of
the Nation's Air Quality, Committee on Environment and Natural Resources, Air Quality Research Subcommittee:
Washington, D.C.
p. 10 National Atmospheric Deposition Program. 1999 Annual Summary, http://nadp.sws.uiuc.edu/lib/data/99as.pdf.
Accessed 11 May 2001.
Regional Effects of Nitrogen Emissions on Health, Visibility, and Materials
p. 13 United States Environmental Protection Agency. O^pneNonattainment Area Map. http://www.epa.gov/agweb. Accessed
11 May 2001.
p. 13 Adapted from: United States Environmental Protection Agency. Number of Unhealthy Days by City, O^pne Only, http:/
/www.epa.gov/oar/aqtrnd99/aqioz.pdf. Accessed 11 May 2001.
p. 14 United States Environmental Protection Agency. 1998. National Air Quality and Emissions Trends Report, 1997. http://
www.epa.gov/oar/aqtrnd97. Accessed 11 May 2001.
p. 14 Elaine McGee. 1997. AcidRain andOurNation's Capital, United States Geological Survey, http://pubs.usgs.gov/gip/
acidrain. Accessed 11 May 2001.
p. 15 Adapted from: United States Geological Survey. 1999. The Quality of Our Nation's WatersNutrients and Pesticides,
United States Geological Survey Circular 1225, 82 p.
-------
Regional Ecological Effects of Nitrogen Deposition
p. 16 Adapted from: Fenn, Mark E., et al. 1998. "Nitrogen Excess in North American Ecosystems: Predisposing Factors,
Ecosystem Responses, and Management Strategies." Ecological Applications 8 (3): 706-733.
p. 17 National Acid Precipitation Assessment Program. 1998. NAPAP Biennial Report to Congress: An Integrated Assessment,
NAPAP: Washington, D.C.
p. 18 Provided by Greg Lawrence, United States Geological Survey, Troy, NY.
p. 18 National Acid Precipitation Assessment Program. 1990. 1990 IntegratedAssessmentReport, NAPAP: Washington, D.C.
p. 18 Adapted from: R. Kent Schreiber. Acid Deposition. United States Geological Survey, National Biological Service.
http://biology.usgs.gov/s+t/frame/u204.htm. Accessed 11 May 2001.
p. 19 Developed by R. Dennis, Atmospheric Sciences Modeling Division, ARL, NOAA and NERL, USEPA.
p. 20 Adapted from: Bricker, Suzanne B.,etal. 1999. National' Estuarine Eutrophication Assessment: Effects of Nutrient Enrichment
in the Nation's Estuaries, National Oceanic and Atmospheric Administration: Silver Springs, MD.
p. 17 Bricker, Suzanne B., et al. 1999. National'Estuarine Eutrophication Assessment: Effects of Nutrient Enrichment in the Nation's
Estuaries, National Oceanic and Atmospheric Administration: Silver Springs, MD.
Efforts to Understand and Reduce NO Emissions
X
p. 22 United States Environmental Protection Agency. Clean Air Markets Division. 2001.
p. 25 OTAG Data Clearinghouse, Northeast Modeling and Analysis Center. "OTAG July 1995 Episode." Obtained from
http://sage.mcnc.org/OTAGDC/otagdc/aqm/uamv/jul95.
p. 29 Stoddard, J. L., C. T. Driscoll, et al. 1998. "A Regional Analysis of Lake Acidification Trends for the Northeastern
U.S., 1982-1994." EnvironmentalMonitoring and'Assessment 51: 399-413.
Conclusions
p. 31 Developed by R. Dennis, Atmospheric Sciences Modeling Division, ARL, NOAA and NERL, USEPA.
-------
§ a
^: &_
-h CO
O C
"D 5'
CD"
CD
CO
o
o
K) ^ -
m
D
O
o
o
CD QJ.
3- CD
Tl
O
CD"
o
CQ
CD
------- |