The AQI color codes are used for both air quality forecasts and for air quality reporting. The forecast, available year-round in the Triad and Charlotte, and April 1 through October 31 in Asheville, Fayetteville, Hickory, and the Triangle, predicts anticipated pollution levels using the AQI color code. Air quality reports give either current pollution levels detected by monitors or air pollution levels that have already occurred, usually during the previous day. For reports of recent air quality levels in many areas of North Carolina, visit the DAQ ozone and particulate matter monitoring website or call 1-888-AIRWISE (1-888-247-9473). Reports of current and recent air quality levels in Mecklenburg County are found at the Mecklenburg County air quality monitoring website or by calling 704-333-SMOG (7664).
What is an Air Quality Action Day? [Back to Top]
An Air Quality Action Day is announced when pollution levels are forecasted to be Code Orange, Red or Purple (levels above the Federal health standard). On Air Quality Action Days, citizens are asked to take ACTION to reduce air pollution and to protect their health. From April 1 through October 31, most Air Quality Action Days will be for ozone, although a few code orange particulate days may occur during this period. From April 1 to October 31, most Air Quality Action Days will be for ozone, although a few code orange particulate days may occur during this period. From November 1 - March 31, Air Quality Action Days during this period should only be for particles.
What can I do to improve North Carolina's air quality? [Back to Top]
Ozone and particle pollution, the two biggest air quality concerns in North Carolina, come from many of the same sources, primarily motor vehicles and industry (including power plants). Our individual activities create air pollution, and all of us have the power to improve air quality through our actions. Try some of the following:
- Leave your car at home. Take the bus, car pool, van pool, walk or ride your bike to your destination.
- Don't drive to lunch. Take a meal or walk to a nearby restaurant instead of driving out to eat during the workday.
- Drive right. When you do drive your car, use cruise control whenever practical and stay within the speed limit. Avoid sudden stops and starts. Plan ahead and combine short trips whenever possible to avoid cold starts. Your vehicle may be your single biggest impact on air quality. Make air quality a priority by factoring emissions and fuel efficiency into your vehicle purchasing decisions. Find how vehicles compare by using the EPA's Green Vehicle Guide or the US Department of Energy's fuel economy website .
- Keep vehicles maintained. Keep your car, boat, and lawn equipment tuned up and follow your car's maintenance schedule. Engines that are well maintained are more fuel-efficient and cause less pollution.
- Check your tire pressure. Keep your tires properly inflated; you'll save gas and reduce tire wear, too.
- Don't idle. Avoid idling in drive-through lanes - park and walk in instead. Idling your vehicle wastes gas and increases pollution, and idling can damage your car more than shutting off and re-starting your engine.
- Refuel at dusk. Postpone refueling your car until after 6 p.m. on Air Quality Action Days. This reduces the emissions during the peak daylight hours when ozone formation is most likely.
- Don't top off your tank. When refueling your vehicle, stop at the click to avoid spilling gas and polluting the air and surface water.
- Reduce use of gasoline-powered lawn equipment.The small engines in lawn care equipment are major polluters. Use hand-powered or electric lawn care equipment whenever possible, and consider landscaping to reduce the amount of grass on your property. On Air Quality Action Days, wait until after 6:00 p.m. to use gas-powered lawn equipment.
- Conserve electricity. In the summer, set your air conditioning at the highest comfortable temperature (try 78 degrees). During winter, try a setting of 68 - 70 degrees to reduce electricity use by your heat pump. Reduce wintertime particulate matter pollution from oil furnaces by keeping them well maintained. Use ceiling fans to increase both cooling and heating efficiency. Turn off appliances when not in use. Look for the Energy Star label when purchasing major appliances.
- Try something different. Use water-based paints and cleaners instead of solvent-based products.
What is the Air Quality Coalition? [Back to Top]
The Air Quality Coalition is a partnership of businesses, governments, and organizations motivated to improve North Carolina's air quality, as well as the quality of life of their employees and members. Coalition organizations inform their employees about air quality by distributing the air quality forecast and providing education about air quality issues and actions. Some Coalition organizations help their employees improve air quality by providing incentive programs for carpooling and transit. Over 500 partners participate in local Air Quality Coalitions in the Asheville, Charlotte, Hickory, Triad, and Triangle areas, educating thousands of people about air quality. If you'd like your organization to become a member of the Air Quality Coalition, send an email to Air.Awareness@ncdenr.gov.
What is North Carolina doing to inform citizens about air pollution and its effects? [Back to Top]
The NC Air Awareness Program was created to inform North Carolina's citizens about air pollution and its effects. The program is an active partnership between the North Carolina Division of Air Quality, county environmental agencies, health departments, local governments, transit providers, businesses, citizen organizations, educators, and the media. The Air Awareness program works to educate the public about air quality issues through the internet, hotlines (1-888-RU4NCAIR), brochures, school visits, public events, local media coverage, and through the Air Awareness Coalition. The program seeks to inform citizens as to how their daily actions affect air quality, and how they can protect their health and the health of their environment by making simple lifestyle adjustments. It's just a matter of taking the time to Think, Act and Breathe.
Where can I get real-time air quality information? [Back to Top]
Statewide air quality information is available from the N.C. Division of Air Quality's website. Current information for Mecklenburg County monitors is available from the Mecklenburg County Air Quality agency or by calling 704-333-SMOG (7664). The N.C. Division of Air Quality is currently working to make more real-time air quality information available on our website.
You can also find maps of current air quality conditions for areas around the country, as well as air quality forecasts, on the EPA's AIRNow website.
Where can I get historical air quality data? [Back to Top]
You can find peak air quality monitor readings for the past 24-36 hours, as well as statistical summaries and reports of past air quality, at the N.C.
Division of Air Quality Ambient Monitoring Section's website. For data from locations nationwide, visit the
EPA Office of Air Quality Planning and Standards Air Pollution Monitoring website . Ozone forecast verifications, past ozone concentration nformation, and ozone monitor statistics are available through the DAQ on the Ozone Concentration Data website.
What is particle pollution? [Back to Top]
Particle pollution, also known as particulate matter pollution or PM, is a
mixture of tiny solids and liquid droplets suspended in air. Airborne particles
are the main ingredient in haze, smoke and airborne dust. Particles are made up
of a variety of components and may include acids, nitrates, sulfates, organic
chemicals, metals, elements from soil or dust, or allergens (for example,
fragments of pollen or mold spores). Particles come in a wide range of sizes.
Those less than 10 micrometers in diameter are so small that they can be
inhaled into the lungs, potentially causing serious health problems. For
comparison, ten micrometers is much smaller than the width of a single human
hair, which is ~70 micrometers in diameter. Particles less than 2.5 micrometers
in diameter are called "fine" particles and are of special concern because
they can penetrate deeply into the lungs. Particles between 2.5 and 10
micrometers in diameter are referred to as "coarse" particles.
Where does particle pollution come from? [Back to Top]
Some particles are directly emitted into the air, like dust, or the
"soot" particles in diesel exhaust. Other tiny particles are
indirectly formed when chemicals like sulfates, nitrates, and carbon condense
and combine in the air. Sources of fine particles include all types of
combustion from a number of sources, including cars and trucks, power plants, other
industry, and residential fireplaces and wood stoves. Because cars and trucks
are a major source, particle levels are generally higher near busy roadways.
Diesel-powered vehicles and engines contribute more than half of motor vehicle
fine particulate emissions. Indoor sources of particle pollution include smoke
from tobacco, candles, wood stoves, fireplaces, and emissions from natural gas
stoves. Sources of coarse particles include crushing or grinding operations,
dust stirred up by vehicles traveling on unpaved roads, and windblown dust.
How do particles affect human health? [Back to Top]
When inhaled, particles can be
deposited in the airways or deep in the lungs. Once deposited, several things
may happen. Particles may be cleared by the body's natural defense mechanisms,
they may accumulate on the surface where they deposit, or they may be absorbed
into the underlying tissues. The soluble components of fine particles, along
with very small ("ultrafine") particles, may enter the bloodstream.
Some particles may react chemically in the body; others remain in their
The most serious effects of
particles are associated with heart or lung disease. Numerous studies have
linked particle pollution to increased admissions to hospitals and emergency
room visits, and even to death from heart or lung diseases. Short-term exposure
has been linked to aggravation of lung diseases, including asthma attacks and
acute bronchitis. In people with heart disease, particles have been linked to
heart attacks and cardiac arrhythmias (Irregular heart rhythms). Recent
evidence suggests that some of these effects may result from very short-term
exposures, possibly as short as an hour. Epidemiologists have found that
mortality rates and hospitalization rates increase when particle pollution
concentrations rise even a moderate amount. Epidemiologists link thousands of
yearly fatal heart attacks in the U.S. to particulates.
A 16-year study published in
March 2002 in the Journal of the American Medial Association provides evidence
that long-term exposure to fine particles significantly increases the risk of
illness and death from lung cancer and heart disease. The level of lung cancer
risk associated with exposure to fine particles emitted by coal-fired power
plants, factories and diesel trucks is comparable to the risk posed by
long-term exposure to second-hand smoke from cigarettes.(1) American Cancer
Society and Harvard University epidemiological studies recently showed that
people living in more polluted cities had an increased risk of premature death
compared to those in cleaner cities.
Particle exposure might also
increase susceptibility to bacterial or viral respiratory infections, leading
to increased risk of pneumonia in vulnerable individuals. In the presence of
pre-existing heart disease, acute bronchitis or pneumonia induced by air
pollutants might precipitate congestive heart failure.
In healthy children and
adults, exposure to elevated particle levels for short periods of time may
cause minor irritation. Most healthy people will recover quickly from these
effects and are unlikely to experience long-term health problems. However,
long-term exposure to particles has been associated with reduction in lung
function and the development of chronic bronchitis.
(1) Pope et al. 2002. Lung
Cancer, Cardiopulmonary Mortality, and Long-term Exposure to Fine Particulate
Air Pollution. J. Am. Med. Assoc. 287(9):1132-1141.
Who is affected by particle pollution? [Back to Top]
Everyone's health can be at risk when particle pollution levels are high, but
some groups of people are also at risk at lower levels, such as those with
heart or lung disease, older adults (men over 45 and women over 55), and
People with heart or lung diseases such as congestive heart
disease, coronary artery disease, asthma, or chronic obstructive pulmonary
disease (COPD) are at risk because particles can aggravate these conditions. In
addition, the obstructed airflow in people with COPD may cause more particles
to deposit in their lungs. People with diabetes may be at increased risk of
serous effects, possibly because of underlying cardiovascular disease.
Older adults are at increased risk, possibly because they are more
likely to have either diagnosed or undiagnosed heart or lung disease or
Children may be more vulnerable to particles because their
lungs are still developing, and they breathe more air in relation to body
weight than do adults. In addition, they spend more time at higher activity
levels, and are more likely to have asthma or acute respiratory diseases.
Factors that increase the risk
of heart attack may also increase your risk from particles. These include age,
family history of heart disease, smoking, high blood pressure, high blood
cholesterol, obesity, physical inactivity and diabetes. The risks of health
effects are increased by physical activity during periods of elevated particle
pollution. When you are physically active, you breathe faster and more deeply,
taking more air and more particles into your lungs. Scientists do not yet know
if pregnant women are at increased risk from particle pollution. Studies
suggest that breathing high particle levels over long periods of time may be
associated with low-birth-weight infants, pre-term deliveries, and fetal and
What are the symptoms of particle pollution exposure? [Back to Top]
If you have lung disease, you may not be able to breathe as deeply or as
vigorously as normal, and you may experience respiratory symptoms such as
coughing, chest discomfort, wheezing, shortness of breath, and unusual fatigue.
If you experience these symptoms, you should reduce exposure and activity
level, and follow the advice of your doctor. If you have asthma, you should
already have an asthma action plan, but you may need to follow it more
carefully when particle levels are high.
If you have heart disease, you can have serious effects, such as heart attacks,
with no warning symptoms. The absence of symptoms does not mean that you are
safe. If you do experience symptoms - such as chest pain or tightness,
palpitations, shortness of breath, or unusual fatigue - contact your doctor as
these symptoms may indicate a serious problem.
Even if you are healthy you may experience temporary symptoms from exposure to
elevated levels of particles. Symptoms may include; irritation of the eyes,
nose and throat, coughing; phlegm; chest tightness; and shortness of breath.
What level of exposure to particulates is considered unhealthy? [Back to Top]
People have experienced health problems from exposure to particles over long
periods (years) and from periods as short as 1 to 24 hours. Epidemiological
studies have reported a linear relationship between exposure and effects;
higher concentrations of particles have a greater effect on the health of populations.
Scientists have not been able to identify a threshold below which health
effects do not occur. According to the World Health Organization, long-term
epidemiology studies show that the risk of premature deaths starts to increase
when the annual average of fine particle concentrations exceeds10 micrograms
per cubic meter. The EPA has set an annual and a 24-hour standard for fine
particulate pollution to protect human health. The annual standard is 15
micrograms per cubic meter. This represents particle levels averaged over an
entire year, and is designed to protect the public from long-term exposure. The
24-hour standard is 35 micrograms per cubic meter, and protects against
short-term exposure to higher particle levels.
How can I reduce my risk from particle exposure? [Back to Top]
Your chances of being affected by particles increase the longer you are active
outdoors and the more strenuous the activity you engage in. If you're involved
in an activity that requires prolonged or heavy exertion, you can reduce the
time you spend on the activity or substitute another activity that requires
less exertion; for example, go for a walk instead of a jog. You can also plan
outdoor activities when and where particle levels are lower. In general, levels
of particles and other pollutants are higher near busy roadways, so avoid heavy
exertion - like jogging or biking - in these areas.
Daily air quality forecasts give notice of anticipated high particle levels. People in at-risk groups should take special care to
reduce exposure at Code Orange air quality levels or higher, and everyone
should exercise caution at code red levels.
Particle levels can sometimes
be elevated indoors, especially if particles in the outdoor air are elevated
and there are additional indoor sources, such as tobacco smoke. Certain filters
are available that can help reduce particle levels indoors. Ozone-producing air
cleaners (sometimes called "activated oxygen" air cleaners) should
not be used in occupied spaces as they may cause unhealthy levels of ozone to
accumulate. You can also reduce indoor sources of particles by eliminating
tobacco smoke and reducing the use of candles, wood-burning stoves and
What time of year is particle pollution a problem? [Back to Top]
Unlike ozone, particle pollution occurs year-round, and particle pollution
levels can be high inside or outside. When particle pollution levels are high
it is important to limit physical activity, even if that activity occurs
indoors. Unusual events sometimes increase particle pollution to high levels.
Occasionally a plume of smoke from a distant forest fire will elevate local
particle levels. After the December 2002 ice storm, many Triangle area
residents without electricity burned wood for warmth. At the same time, an
atmospheric inversion concentrated the wood smoke, resulting in Code Red particle
pollution levels in the Triangle.
What time of day are particle pollutions levels high? [Back to Top]
Unlike ground level ozone pollution, particle pollution levels can be high in
the morning or in the afternoon. It is important to know the Air Quality Index
Color Code forecast for the day and limit or avoid activity - inside or out,
morning or evening - on days when particulate pollution levels are high.
What areas of N.C. have a particle pollution forecast? [Back to Top]Particle pollution forecasts
are available year-round in Charlotte, Fayetteville, the Triangle, the Triad,
Hickory, and the Asheville valleys.
Where can I find the particle pollution forecast? [Back to Top]
Daily air quality forecasts will warn you of expected high particle levels. During the
warm-weather season of April 1 through October 31, the forecasts will also warn of
high ozone levels. You can find the forecast in the weather section of your
local newspaper or during the weather segment of your local television news.
You may also hear it on some radio stations. Some national media, such as USA
Today and The Weather Channel, also provide air quality information.
You can find the particle forecast at NC DAQ Air
Quality Forecast Center website for Asheville, Charlotte, Hickory,
Fayetteville, and the Triangle, and at the Forsyth County Environmental Affairs website for the Triad. You can also call 1-888-RU4NCAIR
(1-888-784-6224) to hear forecasts for both areas. Forecasts are issued at
approximately 3:00 each day, and predict air quality for the following day. In
Mecklenburg County, you can find real-time air quality information for selected
monitors at the Mecklenburg County air quality monitoring website . Monitor data using the state network
can be found at the Ambient Monitoring current data webpage. This information will let you know when local particle levels are already high.
How can I receive the particle pollution forecast directly? [Back to Top]
Any individual or organization can receive the forecast by email through
EnviroFlash. EnviroFlash is sponsored by the EPA and provides air quality
information such as forecasts and action day notifications via email for your
area of interest. To register for EnviroFlash, visit the EnviroFlash sign-up page .
Please note that air quality forecasts are not provided for all regions. The
Division of Air Quality provides forecasts for areas known to have instances of
poor air quality, while areas of generally good air quality do not receive
forecasts. If your location is not near a forecast location, you will be
notified during the signup process.
If you are with a business,
government agency, or organization, consider signing up for your local Air
Quality Coalition. Coalition members distribute the Air Quality Action Day
forecasts to their employees or organization members, and provide air quality
education. In this way, Coalition members help to improve both air quality and
public health. Contact Air.Awareness@ncdenr.gov
or call 1-888-RU4NCAIR for more information.
What can I do to reduce particle pollution? [Back to Top]
Because particle sources include vehicles and power plants, you can help reduce
particle pollution by driving less, keeping your car well maintained, and
conserving energy. Some specific
ways to help are found near the beginning of this document.
One important way to help
reduce particle levels is by avoiding backyard burning,
sometimes called open burning. Burning non-vegetative trash is illegal
everywhere in North Carolina, and burning yard waste is illegal in many
municipal areas with yard waste pickup. Although burning yard waste may seem
harmless, the particle-rich smoke from your backyard fire could harm others in
your community, especially if they have heart or lung problems. Compost or
mulch your yard waste instead.
What is ozone? [Back to Top]
Ozone is an ionic form of oxygen with 3 oxygen atoms (O3). By contrast, the
form of oxygen we breathe has two atoms (O2). The extra oxygen atom makes ozone
very unstable and thus highly reactive. Ozone occurs naturally in the upper
atmosphere, but is created by human activities at ground level. Ozone has the
same chemical structure whether it occurs high above the earth or at ground
level, and can be "good" or "bad," depending on its
location in the atmosphere.
Is ozone good or bad? [Back to Top]
The naturally occurring ozone layer in the upper atmosphere, or stratosphere,
protects the earth from the sun's ultraviolet radiation. Obviously,
stratospheric ozone is "good" ozone, and the depletion of stratospheric ozone continues to be of major concern.
However, ozone does not occur
naturally in the lower atmosphere, except in very small amounts. Most of the
ozone at ground level is produced by human activities. Ground level or
"bad" ozone is an air pollutant that damages human health,
vegetation, and even man-made materials such as fabric and rubber.
Is ozone the same thing as smog? [Back to Top]
The term "smog" is often used to refer to ground-level ozone pollution.
When you see or hear the word smog used in a news report about air pollution,
you can usually assume that the report is referring to ozone pollution. Ozone
combines with particle pollution to form the dirty-looking urban haze that many
people think of as smog. So although ozone and smog are not the same thing,
ozone is a necessary ingredient of smog. However, it's important to remember
that ozone levels can be high even on a clear day with no visible
What North Carolina areas have an ozone problem? [Back to Top]
Typically, high ozone pollution levels occur in urban areas where there are
lots of cars, industry and other sources of combustion. However, ozone can
travel with the wind to rural areas and become a problem in those areas as
well. In North Carolina, our greatest areas of concern are the Charlotte area,
the Triad (Greensboro, Winston-Salem, and High Point), and the Triangle
(Raleigh, Durham, and Chapel Hill). However, several other areas of North Carolina
have a problem with high ozone levels and exceed (have higher values) than the
EPA's 8-hour ozone standard.
How is ozone formed? [Back to Top]
Ground-level ozone forms when nitrogen oxides (NOx) react with volatile organic
compounds (VOCs) in the presence of heat and sunlight.
VOCs, Volatile Organic
Compounds or hydrocarbons, come from man-made sources such as cars, service
stations, dry cleaners and factories as well as natural sources such as trees
and other vegetation. Because VOCs are volatile, or highly reactive, they
evaporate easily and typically have a strong smell. Fumes from gasoline, paint
thinners and solvents, and even printer ink are all VOCs. Not all VOCs smell
"bad". Some good smelling VOCs are the fragrances in perfumes, soaps, and
other consumer products. Naturally occurring VOCs from trees and vegetation are
sometimes called biogenic emissions, while man-made emissions are referred to
NOx is a byproduct of
combustion, and comes from coal-fired power plants, industrial boilers, motor
vehicles, lawn-care equipment and other sources that burn fuel. In some North
Carolina urban areas, up to 70% of ozone-forming NOx comes from motor vehicles.
Efforts to control ozone focus
on NOx because most of it comes from man-made sources that can be controlled.
Reducing VOCs is less effective because pines, oaks and other trees that are so
abundant in the South emit large amounts of hydrocarbons.
Most of the ozone in urban
areas comes from local sources. However, winds can carry ozone from cities to
surrounding rural areas and even to other states. Much of the ozone pollution
at high elevations in the mountains of Western North Carolina is transported by
winds from other states. In mountain valleys, however, ozone-forming pollution
can come from both local and out-of-state sources.
Why is ground-level ozone a problem? [Back to Top]
Ozone is a strong respiratory irritant, and can cause serious health problems,
especially for sensitive groups: children, people with asthma and other
respiratory ailments, and anyone who works or exercises vigorously outdoors.
Symptoms of ozone exposure can include coughing, throat irritation, chest pain,
rapid and shallow breathing, and asthma attacks. Emergency room visits for
asthma have increased as much as 36 percent on high ozone days, according to
some studies. High childhood exposure to ozone pollution may reduce lifetime
lung function. High ozone levels also damage vegetation, reducing growth rates
and crop yields. More details on the health and environmental effects of ozone
can be found later in this section.
What is the ground-level ozone standard in NC? [Back to Top]
The Federal standard for ground-level ozone is 0.075 parts per million (ppm),
averaged over an 8-hour period. This is often referred to as the "8-hour
standard" and replaces an older "1-hour standard" of 0.125 ppm.
Levels of 0.076 ppm and above exceed the Federal ground-level ozone standard.
What does "ppm" mean? [Back to Top]
Parts per million, or ppm, is a ratio that describes how many parts of
something you have per one million equally-sized parts of something else. So,
with the 8-hour standard, the maximum healthy concentration of ground-level
ozone is less than 1/10th of one part of ozone per one million parts of air.
These examples might help you
- If a pie is divided equally into 10
pieces, each piece would be a part-per-ten; i.e., one-tenth of the total pie.
If the pie were cut into 100 pieces, each piece would be one part-per-hundred,
or one percent, of the pie. If this pie is cut into a million pieces, each
piece would be very small and would represent a millionth, or part per million,
of the original pie. If each of the million minute pieces is cut into a
thousand little pieces, each of these new pieces would be a part per billion of
the original pie.
- Four drops of ink in a 55-gallon
barrel of water would produce an ink concentration of 1 ppm.
- One drop of ink in one of the largest tanker trucks used to haul gasoline would represent 1 ppb.
What are the health effects of ground-level ozone? [Back to Top]
Ozone is a strong respiratory irritant. Short-term, infrequent exposure to
ozone can result in throat and eye irritation, difficulty drawing a deep
breath, and coughing. Long-term and repeated exposure to ozone concentrations
above the Federal standard can result in reduction of lung function as the cells
lining the lungs are damaged. Repeated cycles of damage and healing may result
in scarring of lung tissue and permanently reduced lung function. Health
studies have indicated that high ambient ozone concentrations may impair lung
function growth in children, resulting in reduced lung function in adulthood.
As lung function declines in older adults, individuals whose lung function is
already below normal may be especially vulnerable to respiratory problems.
Asthmatics and other
individuals with respiratory disease are especially at risk from elevated ozone
concentrations. Ozone can worsen, and may trigger, asthma attacks. Ozone may
also contribute to the development of asthma. A recent study published in the
British medical journal The Lancet, found a strong association between elevated
ambient ozone levels and the development of asthma in physically active
All children are at risk from
ozone exposure because they often spend a large part of the summer playing
outdoors, their lungs are still developing, they breathe more air per pound of
body weight, and they are less likely to notice symptoms. Children and adults
who frequently exercise outdoors are particularly vulnerable to ozone's
negative health effects, because they may be repeatedly exposed to elevated
ozone concentrations while breathing at an increased respiratory rate.
(2) McConnell et al. 2002.
Asthma in exercising children exposed to ozone: a cohort study. Lancet 359:
What are the harmful environmental effects of ozone pollution? [Back to Top]
Water Pollution: The nitrogen oxides that contribute to ozone pollution
also fall back to the earth as nitrogen compounds, contributing to nutrient
pollution of streams, rivers, and estuaries. As much as half of the nitrogen
pollution in North Carolina's coastal waters may come from air pollution.
Nutrient pollution contributes to algal blooms, reduced oxygen content of
water, and fish kills.
Plant and Crop Damage: Ozone pollution can damage plant tissues, reducing
growth rates and agricultural yields. It interferes with the ability of plants
to produce and store food, making them more susceptible to disease, insects,
other pollutants, and harsh weather. Ground-level ozone damages the foliage of
trees and other plants, impacting the landscape of cities, national parks and
forests, and recreation areas.
How do weather conditions affect ground-level ozone? [Back to Top]
Sunlight, temperature, atmospheric stability, and wind conditions all affect
the formation and accumulation of ground-level ozone. Ultraviolet radiation
from sunlight drives the reaction between NOx and VOCs to form ozone, so ozone
pollution increases on clear or partly cloudy days. Like many chemical
reactions, ozone formation increases as temperatures rise. In addition,
temperature affects ozone-forming emissions (e.g., evaporative emissions of
VOCs and biogenic emissions increase with high temperatures). Atmospheric
stability (temperature change by height) controls the amount of vertical air
mixing that takes place. Strong stability tends to reduce mixing (dilution) of
ground-level ozone and ozone-forming emissions. During atmospheric inversions, air
higher in the atmosphere is warmer than air below, preventing lower air from
rising and mixing. Inversions thus concentrate air closer to the surface,
sometimes resulting in higher ozone levels. Wind conditions affect the
dispersal and dilution of air and pollutants. Calm or light winds allow more
pollution to concentrate in an area. Upper-level winds are also important
because they can transport ozone great distances during the overnight period.
Ozone concentrations tend to be highest on sunny, hot days with little to no
When is the ground-level ozone season in NC? [Back to Top]
Because hot, sunny conditions are needed for elevated ozone levels, ozone is
only a problem during the warm-weather months. The ozone forecast season, when
N.C. Division of Air Quality forecasts daily ozone levels, is April 1 to
What time of day are ground-level ozone levels the highest? [Back to Top]
Ozone begins forming in the morning and formation increases as temperatures
increase during the day. Ozone accumulates through the day, especially when
winds are calm. In most areas of North Carolina, ozone levels peak during
mid-afternoon through early evening, when temperatures are hottest. Ozone
levels decrease as the sun sets, drop at night and are lowest around dawn.
However, at high elevations (above 4,000 feet) in the mountains, ozone levels
can remain high throughout the day and actually reach their highest values
When is it best to do exercise outdoors during ozone season? [Back to Top]
On Ozone Action Days, it's safest to exercise in the morning, when ozone levels
are lowest. Morning is a good time for biking, walking, jogging or other types
of strenuous outdoor activities. At high elevations in the mountains, ozone
levels can remain high throughout the day and night during bad air events - so
people should limit outdoor activities if they notice signs of problems such as
coughing and breathing difficulty.
By paying attention to the
daily ozone forecast, you can plan your exercise schedule. On Ozone Action Days
of Code Orange and above, try to schedule exercise for the morning, and avoid
strenuous exercise in the afternoon. Although ozone levels are generally not as
low at dusk as in the morning, ozone levels during dusk and evening are usually
safe for exercise. On Code Green days, you are safe exercising any time of the
day, and most people are safe exercising on Code Yellow days as well. On
"high" Code Yellow days when the AQI is predicted to be close to 100,
very sensitive people may need to limit or avoid afternoon exertion.
If you are considering exercising
at high elevations in the mountains, the Asheville Ridge Tops forecast will
alert you to days when ozone levels may be elevated during daytime and
What is the ozone forecast? [Back to Top]
The NC Division of Air Quality issues a ground-level ozone forecast every day
from April 1 through October 31 that consists of an Air Quality Index
(AQI) forecast and a corresponding color code. The color code and AQI value
predict the maximum 8-hour ozone concentration for the following day. This
information is distributed via email, media outlets, and the
North Carolina Forecast Center
web site. The ground-level ozone forecast allows citizens not only
to plan outdoor activities to protect their health, but also to take action to
reduce ozone-forming emissions.
When are the ground-level ozone forecasts issued? [Back to Top]
Ground-level ozone forecasts are issued everyday from April 1 through October 31h at 3:00 pm EDT. A
also issued at 3:00 pm EDT, provides a detailed
description of the current ozone and meteorological conditions which the
forecaster has considered in making the forecast. A
is available around 10:00 am EDT each day. The morning
edition provides additional information specifying whether the current forecast
appears to be on track.
Is there a ground-level ozone forecast for my area? [Back to Top]
The NC Division of Air Quality issues ground-level ozone forecasts for the Asheville (Ridge Tops and Valleys), Charlotte, Fayetteville, Hickory, Rocky Mount, and the Triangle regions of North Carolina.
Additionally, the Forsyth County Environmental Affairs Department issues an air quality forecast for the
Triad area. There is a ground-level ozone forecast for your area if you live or
work in one of the counties associated the following forecast regions:
- Asheville: Buncombe, Haywood, Henderson, Jackson, Madison, Transylvania, Swain, and Yancey Counties.
- Hickory: Alexander, Catawba, Southeastern Burke and Southeastern Caldwell Counties.
- Charlotte: Cabarrus, Gaston, Lincoln, Mecklenburg, Rowan, Union, and Southern Iredell Counties, NC; and York County SC.
- The Triad: Alamance, Caswell, Davidson, Davie, Forsyth, Guilford, Randolph, Rockingham, and Stokes Counties.
- The Triangle: Chatham, Durham, Franklin, Granville, Johnston, Orange, Person, Vance, and Wake Counties.
- Fayetteville: Harnett and Cumberland Counties.
Where can I find the ozone forecast? [Back to Top]
Between April 1 through October 31, look for the ozone forecast in the weather
section of your local newspaper and during the weather segment of your local
television news. You may also hear it on some radio stations. Some national
media, such as USA Today and The Weather Channel, also provide air quality
You can find the forecast at the NC DAQ Air Quality Forecast Center website
for all areas except the Triad, and at the Forsyth County Environmental Affairs Department for the Triad. You can also call
1-888-RU4NCAIR (1-888-784-6224) to hear forecasts for all areas. Forecasts are
issued at approximately 3:00 each day, and predict air quality for the next
How can I receive the ground-level ozone forecast directly? [Back to Top]
Any individual or organization
can receive the forecast by email through EnviroFlash. EnviroFlash is sponsored
by the EPA and provides air quality information such as forecasts and action
day notifications via email for your area of interest. To register for
EnviroFlash, visit the EnviroFlash sign-up page . Please note that air quality
forecasts are not provided for all regions. The Division of Air Quality
provides forecasts for areas known to have instances of poor air quality, while
areas of generally good air quality do not receive forecasts. If your location
is not near a forecast location, you will be notified during the signup
If you are with a business,
government agency, or organization, consider signing up for your local Air
Quality Coalition. Coalition members distribute the Air Quality Action Day
forecasts to their employees or organization members, and provide air quality education.
In this way, Coalition members help to improve both air quality and public
health. Contact Air.Awareness@ncdenr.gov
or call 1-888-RU4NCAIR for more information.
How can I take action to reduce ozone pollution? [Back to Top]
Because the biggest source of ozone pollution in most areas is cars and trucks,
taking steps to reduce driving your car will be the most helpful. Conserving
electricity will reduce ozone pollution resulting from power plant emissions. A
list of specific things you
can do is near the top of this document.
Your business, citizen
organization, or agency can help reduce ozone pollution by joining the Air
Quality Coalition. Coalition partners distribute the Air Quality Action Day
forecasts to their employees or organization members, and provide air quality
education. The combined efforts of over 500 Coalition partners statewide reach
many thousands of people, improving both air quality and public health. Contact
Air.Awareness@ncdenr.gov or call
1-888-RU4NCAIR for more information.
Where can I find more air quality information? [Back to Top]