NOx - How Nitrogen Oxides Affect
the Way We Live and Breathe
| Nitrogen oxides, or NOx, is the generic term
for a group of highly reactive gases, all of which contain nitrogen
and oxygen in varying amounts. Many of the nitrogen oxides are
colorless and odorless. However, one common pollutant, nitrogen
dioxide (NO2) along with particles in the air can often be
seen as a reddish-brown layer over many urban areas. Nitrogen oxides
form when fuel is burned at high temperatures, as in a combustion
process. The primary sources of NOx are motor vehicles, electric
utilities, and other industrial, commercial, and residential sources
that burn fuels.
courtesy of EPA - Environmental Protection Agency |
![Plant Image [courtesy of EPA - Environmental Protection Agency]](images/chfphoto.gif) NOx
- is one of the main ingredients involved in the formation of
ground-level ozone, which can trigger serious respiratory problems.
- reacts to form nitrate particles, acid aerosols, as well as NO2,
which also cause respiratory problems.
- contributes to formation of acid rain.
- contributes to nutrient overload that deteriorates water
quality.
- contributes to atmospheric particles, that cause visibility
impairment most noticeable in national parks.
- reacts to form toxic chemicals.
- contributes to global warming.
NOx and the pollutants formed from NOx can
be transported over long distances, following the pattern
of prevailing winds in the U.S. This means that problems associated
with NOx are not confined to areas where NOx are emitted. Therefore,
controlling NOx is often most effective if done from a regional
perspective, rather than focusing on sources in one local area.
 NOx
emissions are increasing.
Since 1970, EPA has tracked emissions of the six principal air
pollutants - carbon monoxide, lead, nitrogen oxides, particulate
matter, sulfur dioxide, and volatile organic compounds. Emissions of
all of these pollutants have decreased significantly except for NOx
which has increased approximately 10 percent over this period.
|
NOx causes a wide variety of health
and environmental impacts because of various compounds and derivatives
in the family of nitrogen oxides, including nitrogen dioxide, nitric
acid, nitrous oxide, nitrates, and nitric oxide.
![Ground-level Ozone (Smog) [courtesy of EPA - Environmental Protection Agency]](images/car.gif) |
Ground-level
Ozone (Smog) - is formed
when NOx and volatile organic compounds (VOCs) react in the
presence of heat and sunlight. Children, people with lung diseases
such as asthma, and people who work or exercise outside are
susceptible to adverse effects such as damage to lung tissue and
reduction in lung function. Ozone can be transported by wind
currents and cause health impacts far from original sources.
Millions of Americans live in areas that do not meet the health
standards for ozone. Other impacts from ozone include damaged
vegetation and reduced crop yields
|
![Acid Rain [courtesy of EPA - Environmental Protection Agency]](images/rain.gif) |
Acid
Rain
- NOx and sulfur dioxide react with
other substances in the air to form acids which fall to earth as
rain, fog, snow or dry particles. Some may be carried by wind for
hundreds of miles. Acid rain damages; causes deterioration of
cars, buildings and historical monuments; and causes lakes and
streams to become acidic and unsuitable for many fish.
|
![Particles [courtesy of EPA - Environmental Protection Agency]](images/lungs.gif) |
Particles
- NOx reacts with ammonia, moisture, and other compounds to form
nitric acid and related particles. Human health concerns include
effects on breathing and the respiratory system, damage to lung
tissue, and premature death. Small particles penetrate deeply into
sensitive parts of the lungs and can cause or worsen respiratory
disease such as emphysema and bronchitis, and aggravate existing
heart disease. |
![Water Quality Deterioration [courtesy of EPA - Environmental Protection Agency]](images/water.gif) |
Water Quality
Deterioration - Increased
nitrogen loading in water bodies, particularly coastal estuaries,
upsets the chemical balance of nutrients used by aquatic plants
and animals. Additional nitrogen accelerates "eutrophication,"
which leads to oxygen depletion and reduces fish and shellfish
populations. NOx emissions in the air are one of the largest
sources of nitrogen pollution in the Chesapeake Bay.
|
![Global Warming [courtesy of EPA - Environmental Protection Agency]](images/world.gif) |
Global Warming
- One member of the NOx, nitrous oxide, is a greenhouse gas. It
accumulates in the atmosphere with other greenhouse gasses causing
a gradual rise in the earth's temperature. This will lead to
increased risks to human health, a rise in the sea level, and
other adverse changes to plant and animal habitat.
|
![Toxic Chemicals [courtesy of EPA - Environmental Protection Agency]](images/poison.gif) |
Toxic Chemicals
- In the air, NOx reacts readily with common organic chemicals and
even ozone, to form a wide variety of toxic products, some of
which may cause biological mutations. Examples of these chemicals
include the nitrate radical, nitroarenes, and nitrosamines. |
![Visibility Impairment [courtesy of EPA - Environmental Protection Agency]](images/eye.gif) |
Visibility
Impairment - Nitrate particles and nitrogen dioxide can
block the transmission of light, reducing visibility in urban
areas and on a regional scale in our national parks.
Reference:
http://www.epa.gov/air/urbanair/nox/hlth.html |
|
|
