What is ozone? [Back to Top]
Ozone is a highly reactive gas that forms in the atmosphere when three (3) atoms of oxygen are combined (O3) through a chemical reaction. In contrast, the oxygen gas we breathe is chemically formed from two (2) atoms of oxygen (O2) and is stable. Ozone is not emitted directly into the air but, at ground level, is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Ozone has the same chemical structure whether it occurs high above the earth or at ground level, and it can be "good" or "bad," depending on its location in the atmosphere.

Is ozone good or bad? [Back to Top]
Ozone occurs in two layers of the atmosphere. The layer surrounding the earth's surface is the troposphere. All animal and plant life is contained within the troposphere. Here, ground-level or "bad" ozone is an air pollutant that damages human health, vegetation, and many common materials. Ground-level ozone is primarily formed as a result of human activities. The troposphere extends to a level about 10 miles up, where it meets the second layer of the atmosphere, the stratosphere. In this second layer of the atmospheric, the stratospheric or "good" ozone layer extends upward from about 10 to 30 miles. The stratospheric ozone layer naturally occurs and protects life on Earth from the sun's harmful ultraviolet rays (UV-b).

Where is ozone a problem? [Back to Top]
Ground-level ozone is a problem anywhere it exists. Typically, it is produced in urban areas where there are lots of cars, industry, and other sources of combustion. Ozone can travel with the wind to other places and become a problem there, too. In North Carolina, our greatest areas of concern are the greater Charlotte area, the Triad (Greensboro, Winston-Salem, and High Point), and the Triangle (Raleigh, Durham, and Chapel Hill). Each of these areas has had a violation of the federally enforced one-hour ozone standard in previous years. Future growth projections in population and vehicle use indicate that these areas along with other communities of North Carolina could potentially violate the proposed eight-hour federal standard.

How is ozone formed? [Back to Top]
Cars, trucks, power plants, factories and other sources emit air pollutants that chemically react to form ozone as a secondary pollutant. Ground-level ozone forms when nitrogen oxides (NOx) react with volatile organic compounds (VOCs) in the presence of sunlight and heat. Sunlight is necessary to start the chemical reactions that form ozone, and heat is important to make the chemical reactions more efficient.

VOCs, 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. NOx, a byproduct of combustion, comes from power plants, industrial boilers, motor vehicles, lawn-care equipment and other sources that burn fuel.

Efforts to control ozone focus on NOx because most of it comes from man-made sources that are concentrated in urban areas. Reducing VOCs is less effective because pines, oaks and other trees that are so abundant in the South emit large amounts of hydrocarbons.

Ozone levels generally are higher in urban areas, which contain more cars, industry and other emissions 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 unhealthy to breathe, particularly among 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.

High ozone levels can damage leaves on trees and crops, reducing growth rates and crop yields. In 1995, ground-level ozone caused $2.7 billion in crop damage nationwide, according to the U.S. Environmental Protection Agency. Due to its reactive nature, ozone also can prematurely degrade and wear out rubber, paints and other materials.

Ozone is primarily a problem during the summer months, when heat and sunlight are more intense. Ozone levels also vary on a daily basis. Ozone levels peak in the afternoon, when temperatures are higher, and then drop at night in most of North Carolina. However, ozone levels can remain high throughout the day and night at or near mountain ridge tops. Specific and complex meteorological conditions can cause ozone levels to remain high during the overnight period in higher elevations of the mountains.

You can prevent unhealthy ozone exposure by limiting outdoor work and exercise in the afternoons on high ozone days. Ozone levels generally are much lower in the mornings, so limit exposure by working and exercising outdoors before noon. Ozone generally is not a problem indoors because air conditioners and household furnishings filter it out.

How do we test for ground-level ozone? [Back to Top]
Ground-level ozone can be detected by a number of methods, but sensitive ozone measurements require a highly specialized piece of chemical analysis equipment. The ozone monitors operated and maintained by the NC Division of Air Quality use an ultra-violet absorption technique to determine the ground-level ozone concentration to the nearest one-hundredth of a part per million (ppm) or the nearest part per billionth (ppb).

The NC Division of Air Quality operates an expansive network of ozone monitors throughout North Carolina. Additionally, the Charlotte-Mecklenburg Department of Environmental Management, the Forsyth County Environmental Affairs Department, the Western North Carolina Regional Air Quality Agency, and the Eastern Band of Cherokee Indians, operate ozone monitors in specific regions of the state. This combined ground-level ozone monitoring network includes 43 urban and rural monitoring sites as well as three monitoring sites at or near the top of mountains in western North Carolina. There is even a unique series of three ozone monitors mounted vertically on a television tower southeast of Raleigh.

What is the ground-level ozone standard in NC? [Back to Top]
North Carolina has adopted the proposed Federal standard of 0.08 parts per million of ozone averaged over an 8-hour period. (Parts per million, or ppm, is used to express concentration.)

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:

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 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. To give you an idea of how little this would be, a pinch of salt in 10 tons of potato chips is also a part per billion (ppb). Thus, a part per billion of the pie would be invisible to you.

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]
Ground-level ozone can cause acute respiratory problems, aggravate asthma, temporarily decrease lung capacity (from 15 to 20 percent in a healthy adult), cause inflammation of lung tissue, increase hospital admissions and emergency room visits, and impair the immune system making you more susceptible to respiratory illness (e.g. bronchitis, and pneumonia). People may notice that they cough more or have trouble breathing on high ozone days.

Repeated exposure to ozone pollution may cause permanent damage to the lungs. Even when ozone is present in low levels, inhaling it triggers a variety of health problems including chest pains, coughing, nausea, throat irritation, and congestion. It also can worsen bronchitis, heart disease, emphysema, and asthma, and reduce lung capacity.

Healthy people also experience difficulty in breathing when exposed to ozone pollution. Because ozone pollution usually forms in hot weather, anyone who spends time outdoors in the summer may be affected, particularly children, the elderly, outdoor workers and people exercising. Millions of Americans live in areas where the national ozone health standards are exceeded.

Ground-level ozone damages plant life and is responsible for 500 million dollars in reduced crop production in the United States each year. It interferes with the ability of plants to produce and store food, making them more susceptible to disease, insects, other pollutants, and harsh weather. "Bad" ozone damages the foliage of trees and other plants, ruining the landscape of cities, national parks and forests, and recreation areas.

How do weather conditions affect ground-level ozone? [Back to Top]
The relative influences of sunlight, temperature, atmospheric stability, surface winds, and winds aloft play a significant role in the formation and accumulation of ground-level ozone. Ultraviolet radiation (sunlight) is needed to form ground-level ozone. Clear to partly cloudy sky conditions are needed to allow enough sunlight to produce enhanced concentrations of ground-level ozone. When sky conditions allow sufficient ultraviolet radiation to reach the ground, temperatures increase. The rate at which ground-level ozone is produced increases as temperatures rise. Additionally, temperatures can affect 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 mixing that takes place. Strong stability tends to reduce mixing (i.e., reduce dilution) of precursor pollutants and ground-level ozone. Surface wind speeds control the degree of ventilation. Calm or light winds produce little ventilation allowing emissions and ground-level ozone to accumulate in a given volume of air. Winds aloft are important because they can transport ozone and precursors great distances during the overnight period.

When is the ground-level ozone season in NC? [Back to Top]
The ground-level ozone season occurs during the warm-season months, when the days are warmer and longer. The period of May 1st through September 30th is considered the ground-level ozone season in North Carolina. To identify and analyze this season, the NC Division of Air Quality begins monitoring for ground-level ozone at the beginning of April and continues the monitoring through the end of October.

During the warm-season in North Carolina, the northern hemisphere of the earth is tilted toward the sun. The sun's rays hit the ground more directly and warm the atmosphere more efficiently than in the wintertime. This tilt toward the sun also results in an increase of daylight hours. The warmer and longer days allows for more ground-level ozone production than at any other time of the year.

What time of day are the ground-level ozone levels the highest? [Back to Top]
Sunlight is necessary to start the chemical reactions that form ozone, and heat is important to make the chemical reactions more efficient. Ozone is primarily a problem during the summer months when long days deliver plenty of sunlight and when temperatures are warmest. In most areas of North Carolina, ozone levels peak during mid-afternoon through evening, when temperatures are higher, then 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 overnight.

When is it best to do vigorous outdoor exercises during the ground-level ozone season? [Back to Top]
It is safe on ozone action days to exercise in the morning, because ozone does not usually reach unhealthy levels until the afternoon when temperatures are the hottest. 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.

What is NC doing to inform citizens about ground-level ozone and its effects? [Back to Top]
The NC Air Awareness Program was designed to inform North Carolina's citizens about ground-level ozone and its effects. Through our web site, toll-free hotline, brochures, school visits, public events, local media coverage, interactions with local business coalitions and government, and participation with citizens groups we work to educate the public on air quality issues particularly ground-level ozone its formation, effects, and sources. This Program is designed to help educate the citizens of North Carolina on how their daily actions affect air quality and help the public make informed decisions about their activities.

What is a ground-level ozone forecast? [Back to Top]
The NC Division of Air Quality issues a next day ground-level ozone forecast everyday from May 1st through September 30th that consists of a color-coded forecast and a corresponding Air Quality Index (AQI) number. The color code and AQI value provided in the forecast equates to the maximum 8-hour ozone concentration that is anticipated for that area. This information is distributed via email, fax, media outlets, and the North Carolina Ozone Forecast Center web site. The dissemination of a ground-level ozone forecast information allows citizens not only to make wise decisions regarding their health and outdoor activity levels, but also to take action to reduce ozone-forming emissions.

What are the color codes? [Back to Top]
There are five color codes that describe air quality conditions in North Carolina: Green, Yellow, Orange, Red, and Purple. These color codes are based on EPA's Air Quality Index (AQI) and make it easier for people to understand quickly the significance of air pollution levels in their communities. Each color code represents a specific AQI category and the related cautionary information for that AQI category. The color codes are further defined on the AQI Color Code Guide.

What is "AQI"? [Back to Top]
The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health concerns you should be aware of. The AQI focuses on health effects that can happen within a few hours or days after breathing polluted air. EPA uses the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The AQI reported on the Division of Air Quality's ozone forecast website is for ozone only, this may differ from what is reported in the paper if another pollutant has a greater AQI value for the day.

You can think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health danger. For example, an AQI value of 50 represents good air quality and little potential to affect public health, while an AQI value over 300 represents hazardous air quality.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. So, AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher.

What is an Ozone Action Day? [Back to Top]
An Ozone Action Day occurs when ozone levels are forecasted to be a Code Orange, Red or Purple. On these days, ozone concentrations are predicted to exceed the proposed Federal standard of 0.08 parts per million averaged over an 8-hour period. (Parts per million, or ppm, is used to express concentration.) Ozone levels above the standard are considered unhealthy to breathe, particularly among sensitive groups. Most ozone action days occur during the warmer months, from May through September. When the NC Division of Air Quality (NCDAQ) expects ground-level ozone concentrations to reach the standard or above in one of the forecast areas, NCDAQ issues a forecast for an Ozone Action Day, indicating the expected color code as well as the numerical Air Quality Index (AQI) value.

When are the ground-level ozone forecasts issued? [Back to Top]
Ground-level ozone forecasts are issued everyday from May 1st through September 30th at 3:00 pm EDT. A "forecast discussion", also issued at 3:00 pm EDT, provides a detailed description of the current ozone and meteorological conditions which the forecaster has addressed in making the forecast. Also, a "morning edition" 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, Hickory, Charlotte, Triangle (Raleigh, Durham, and Chapel Hill), and Fayetteville metropolitan regions of North Carolina. Additionally, the Forsyth County Environmental Affairs Department issues an air quality forecast for the Triad (Greensboro and Winston-Salem) metropolitan region. Each metropolitan forecast region consists of multiple counties that contain several communities and small towns in addition to the larger cities. There is a ground-level ozone forecast for your area if you live or work in one of the counties associated with a forecast region listed below:

• Asheville: Buncombe, Haywood, Henderson, Jackson, Madison, Transylvania, Swain, and Yancey Counties
• Hickory: Alexander, Catawba, Southeastern Burke and Southeastern Caldwell Counties
• Charlotte: Mecklenburg, Gaston, Lincoln, Cabarrus, Rowan, Union, York, and the Southern Third of Iredell Counties
• The Triad: Alamance, Caswell, Davidson, Davie, Forsyth, Guilford, Randolph, Rockingham, and Stokes Counties
• The Triangle: Chatham, Durham, Franklin, Johnston, Orange, Wake, and the Southern Portion of Granville Counties
• Fayetteville: Harnett and Cumberland Counties

How can I receive the ground-level ozone forecast? [Back to Top]
To receive the forecast each day during the season, an individual, company, or organization can sign up to be a member of the air quality coalition in their area and receive an e-mail or fax notification each day at 3:30 pm. An electronic form is found at the following web address: http://www.daq.state.nc.us/airaware/coalition/raqc1.pdf

You can also check our Ozone Forecast website each day at http://www.daq.state.nc.us/airaware/ozone/ or you can call our toll-free hotline 1-888-RU4NCAIR (1-888-784-6224) or watch your local television weather forecast each day to find out the color code.

What can I do? [Back to Top]

• Take your lunch.
  Or walk to a nearby restaurant - this reduces the number of vehicles on the road during the daylight hours.
• Drive it right.
  When you do drive your car, use cruise control whenever practical and stay within the speed limit. Avoid sudden stops and starts, and avoid idling for long periods of time. Plan your trips so that you combine short trips whenever possible.
• Do it at dusk.
  Postpone refueling your car until after 6 pm. This reduces the emissions during the peak daylight hours when ozone formation is most likely. Don't "top off" the tank, that is stop adding gasoline, after the pump has automatically shut itself off. This will avoid spills of gasoline and unnecessary VOC emissions.
• Stay tuned.
  Keep your car, boat, and lawn equipment tuned up. Engines that are well-maintained are more fuel efficient and emit less air pollutants. Get a tune up a once a year tune up. After all it makes good economical and environmental sense.
• Leave your car.
  Take the bus, car pool, van pool, walk or ride your bike to your destination.
• Conserve electricity.
  When at home, set your thermostat at the highest temperature at which you are comfortable (try 78 degrees). When everyone is away or asleep, set the thermostat at a warmer temperature. Use a ceiling fan to circulate the cool air. Turn off appliances when not in use.
• Cut it out.
  Try not to cut the grass. Use hand-powered or electric lawn care equipment whenever possible. If you must use gas-powered equipment, wait until after 6:00 pm.
• Try something different.
  Use water-based paints and cleaners instead of solvent-based products.

What are common mistakes that I make on a daily basis that affect air quality? [Back to Top]
There are many common mistakes that people make on a daily basis that inadvertently affects the quality of the air we breathe. Here are several ways to avoid making many of the common mistakes:

• Checking for the Energy Star label on electrical appliances
• Going in to a building (bank, fast food, restaurant, etc.) rather than idling at the drive through
• Following the maintenance schedule on your vehicle
• Keeping your vehicle tires properly inflated
• The fuel efficiency of a vehicle when purchasing
• Servicing your vehicle as soon as the "check engine" or "service engine soon" light comes on
• Raking rather than using a gas or electric powered leaf blower
• Using a push mower when it is feasible rather than a gas or electric powered lawn mower
• Combining errands on the same trip
• How many disposable products you use on a daily basis and choosing reusable alternative
• Using energy efficient light bulbs
• Having your house checked for possible energy leaks
• How you have landscaped your lawn (xeriscaping your lawn to reduce chemicals and mowing needed, adding trees to provide shade and reduce air conditioning usage)
• Choosing products that have less packaging

Where can I get real-time air quality information? [Back to Top]
Air quality forecasts for NC locations are available from the NC Ozone Forecast Center or by calling the toll-free Air Awareness hotline: 1-888-RU4 NCAIR (784-6224).

The Division of Air Quality posts some of the monitored (observed) air quality data we collect on our web site <http://daq.state.nc.us/>. Click on the link to Monitoring & Emissions Data then on Real-time Data.

Real-time data from the Triad area is available from the Forsyth County Environmental Affairs Department.

There are also links to air quality forecasts and to map plots of observed data from (as well as links to) other areas nationwide available in near real-time from the EPA's AIRNow web site.

If you don't have ready access to the Internet, real-time Air Quality Indices (AQI) at several urban locations in North Carolina are reported to the public on a 24-hour continuous basis by a computerized voice recording that is updated every four hours. In Mecklenburg County, call (704) 333-7664. For the AQI values from Raleigh-Durham, Greensboro-Winston-Salem, Greenville-Pitt Co., Wilmington, Fayetteville, and Asheville, call toll free (888) AIR-WISE (247-9473).

The Air Quality Index may also be reported in the next day's newspapers located in those areas as well as in some media outlets such as USA Today and The Weather Channel.

Where can I get historical air quality data? [Back to Top]
Data archives and statistical summaries for North Carolina air quality monitoring sites are available on the NC Division of Air Quality web site. For data from locations nationwide, visit the EPA's Office of Air Quality Planning and Standards Air Pollution Monitoring web site.

Ozone forecast verification, ozone concentration graphics, and ozone monitor statistics are available from the NC Ozone Forecast Center.

Where can I find more information? [Back to Top]
Statewide: NC Air Awareness Program, Division of Air Quality, toll free hotline 1-888-RU4NCAIR (1-888-784-6224), http://daq.state.nc.us

Charlotte Area: Mecklenburg County Department of Environmental Protection, (704) 336-5500, http://www.co.mecklenburg.nc.us/coenv/

Triad Area: Forsyth County Environmental Affairs Department, (336) 727-8064, http://www.co.forsyth.nc.us/EnvAffairs/

Asheville Area: Western North Carolina Air Pollution Control Agency, (828) 255-5655, http://www.wncair.org/

Health and Ozone: NC Division of Public Health, Occupational and Environmental Epidemiology, (919) 733-3410, http://www.dhhs.state.nc.us/ozone.htm

National: US Environmental Protection Agency, http://www.epa.gov/airnow/

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