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|Ozone: The Good and The Bad|
Ozone: Good Up High, Bad Nearby
In North Carolina, ozone is the most widespread air quality problem and the main component in urban smog. Smog also contains dust, soot and other pollutants that can cause a dirty brown haze. But ozone, which is a colorless and odorless gas, can reach high levels even on sunny, clear days with little haze.
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.
Health and Environmental Concerns
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. In most areas of North Carolina, ozone levels peak in the afternoon, when temperatures are higher, and then drop at night. In the mountains, however, ozone levels can remain high throughout the day and night at altitudes above 4,000 feet.
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 it is filtered out by air conditioners and household furnishings.
Ozone forecasts currently are available in the following metropolitan areas: Asheville, Charlotte, Fayetteville, Hickory, the Triad and the Triangle. Many television news shows and newspapers publicize ozone forecasts in their weather reports. Citizens also can obtain forecasts by:
Ozone forecasts are a key part of the N.C. Air Awareness Program, which educates and informs the public about air pollution, its causes and effects, and ways to prevent it. The Air Awareness Program also sponsors:
Frequently Asked Questions About Ozone
What are ozone action days?
Is it safe to go outside and exercise on ozone action days?
Are some people more sensitive to ozone?
What is North Carolina doing to reduce ozone pollution?
How can individuals help reduce ozone pollution?
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