Guide for Nitrogen Dioxide
Air Quality Index
Good
(0-50)
Moderate
(51-100)
Protect Your Health Near Roadways
No health impac
ected when air quality is in this range.
-ange.
Individuals who are unusually sensitive to NO2 should consider
limiting prolonged outdoor exertion.
Unhealthy for Sensitive Groups
(101-150)
Unhealthy
(151-200)
The following groups should limit prolonged outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults
The following groups should avoid prolonged outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults
Everyone else should limit prolonged outdoor exertion.
Very Unhealthy
(201-300)
The following groups should avoid all outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults
Everyone else should limit outdoor exertion.
What You Should Know About Nitrogen Dioxide and Your Health
• Nitrogen dioxide comes from vehicle, power plant, and industrial emissions and off-road sources such
as construction, lawn and gardening equipment.
• People who live or work near busy roadways can experience high exposures.
• Find out more about air quality through TV, radio, newspapers, AIRNow (www.airnow.gov) and
EnviroFlash (www.enviroflash.info), so you can take steps to protect your health.
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Revisions to the National Ambient Air
Quality Standards for Nitrogen Dioxide
On January 22,2010, EPA strengthened the health-
based National Ambient Air Quality Standard
(NAAQS) for nitrogen dioxide (NC>2). EPA set a
new I -hour NO2 standard at the level of 100 parts
per billion (ppb). EPA also retained the current annual
average NO2 standard of 53 ppb.
The new I -hour standard will protect public health
by limiting people's exposures to short-term peak
concentrations of NO2 - which primarily occur near
major roads. Community-wide NC>2 concentrations
will be limited to levels below those that have been
linked to respiratory-related emergency room visits
and hospital admissions.
Additionally, EPA established new ambient air
monitoring and reporting requirements for NC>2.
In urban areas, monitors are required near major
roads and in other locations where maximum
concentrations are expected. EPA has placed a
number of monitors in locations to help protect
communities that are susceptible and vulnerable to
NC>2-related health effects.
of adverse effects on the respiratory system. NOx
reacts with ammonia, moisture, and other compounds
to form small particles. These small particles can
penetrate deeply into sensitive parts of the lungs.
How does nitrogen dioxide affect health?
Scientific evidence links short-term NC>2 exposures,
ranging from 30 minutes to 24 hours, with adverse
respiratory effects including airway inflammation in
healthy people and increased respiratory symptoms in
people with asthma.
Studies also show a connection between short-term
exposure and increased emergency room visits and
hospital admissions for respiratory illnesses.
Who is sensitive to nitrogen dioxide?
Individuals who spend time on or near major roads
can experience NC>2 exposures considerably higher
than occur away from roads. These exposures are of
particular concern for sensitive groups, such as people
with lung disease including asthma.
What is nitrogen dioxide and where does it
come from?
EPA's NAAQS for NC>2 is designed to protect against
exposure to the entire group of nitrogen oxides
(NOx). NO2 is the component of greatest concern
and is used as the indicator for the larger group of
NOx. The sum of nitric oxide (NO) and NO2 is
commonly called NOx. Other nitrogen oxides include
nitrous acid and nitric acid. NOx reacts with volatile
organic compounds to form ozone.
NO2 forms from the emissions of vehicles, power
plants, industrial sources, and off-road equipment,
such as construction vehicles and lawn and garden
equipment. In addition to contributing to ground-
level ozone formation, NO2 is linked with a number
Does my community have unhealthy NO2 levels?
Unlike ozone and particle pollution, which can be
of concern over large regions, NO2 levels are
appreciably higher in close proximity to pollution
sources (e.g., vehicles on major freeways, factories).
Health effects associated with NO2 are much less
likely farther away from these pollution sources.
NO2 in heavy traffic or on freeways can be two times
as high as levels measured in residential areas or on
lesser traveled roads. Monitoring studies have shown
that within approximately 50 meters of heavy traffic/
freeways, NC>2 concentrations may be 30 to 100
percent higher.
What You Can Do To Reduce NO2 Emissions
• Carpool or use public transportation.
• When air quality is healthy, bike or walk instead of driving.
• Combine errands to reduce vehicle trips.
• Limit engine idling.
• When refueling avoid spilling fuel. Tighten gas cap securely.
• Keep your car, boat, and other engines tuned up.
• Inflate car tires to the recommended pressure.
• Conserve energy at home and at work
Office of Air and Radiation (6301 A)
EPA Document # EPA-456/F-10-002
www.airnow.gov
October 2010
oEPA
United States
Environmental Protection
Agency
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