Ozone (O3) is a highly reactive gas composed of three oxygen atoms. Depending on where it is in the atmosphere, ozone affects life on Earth in either good or bad ways.
Stratospheric ozone is formed naturally through the interaction of solar ultraviolet (UV) radiation with molecular oxygen (O2). The stratospheric “ozone layer” extends from approximately six to thirty miles above the Earth’s surface and reduces the amount of harmful UV radiation reaching the Earth’s surface.
Tropospheric, or ground-level, ozone forms primarily from reactions between two major classes of air pollutants: volatile organic compounds (VOCs) and nitrogen oxides (NOx). These reactions depend on the presence of heat and sunlight, meaning more ozone forms in the summer months.
NOx is emitted by cars, power plants, industrial plants, and other sources. Significant sources of VOC emissions include gasoline pumps, chemical plants, oil-based paints, auto body shops, print shops, consumer products and some trees. Significant human-made sources of VOC emissions include gasoline pumps, chemical plants, oil-based paints,auto body shops, print shops, and some consumer products.
How Can Ozone Be Both Good and Bad?
Ozone occurs in two layers of the atmosphere. The layer closest to the Earth’s surface is the troposphere. Here, ground-level or “bad” ozone is an air pollutant that is harmful to breathe and it damages crops, trees and other vegetation. It is a main ingredient of urban smog. The troposphere generally extends to a level about 6 miles up, where it meets the second layer, the stratosphere. The stratosphere or “good” ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun’s harmful ultraviolet (UV) rays.
Ozone Season: Not Just Life in the Big City
May through September is known as “ozone season;” however, ozone pollution can occur throughout the year in some southern locations. Ozone pollution isn’t limited to big cities like Los Angeles, Houston and New York. It’s also found in smaller cities like Raleigh, NC and Cincinnati, OH. And it can be a problem in rural areas, including some national parks. Ozone and the pollutants that react to form it (NOx and VOCs) can also be carried on the wind to affect air quality in urban and rural areas many miles away.
How Does “Bad” Ozone Affect Human Health and the Environment?
Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. “Bad” ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue.
Healthy people also experience difficulty breathing when exposed to ozone pollution. Because ozone forms in hot weather, anyone who spends time outdoors in the summer may be affected, particularly children, outdoor workers and people exercising. Millions of Americans live in areas where the national ozone health standards are exceeded.
Ground-level or “bad” ozone also damages vegetation and ecosystems. It leads to reduced agricultural crop and commercial forest yields, reduced growth and survivability of tree seedlings, and increased susceptibility to diseases, pests and other stresses such as harsh weather. In the United States alone, ground-level ozone is responsible for an estimated $500 million in reduced crop production each year. Ground-level ozone also damages the foliage of trees and other plants, affecting the landscape of cities, national parks and forests, and recreation areas.
Tips For Reducing Ozone:
1. Share a ride or take a bus to work.
2. Avoid the morning rush hour traffic.
3. For short trips, use a bicycle.
4. “Brown bag it” for lunch instead of dining out.
5. Combine errands into one trip.
6. Postpone refueling until after 7 p.m.
7. Don’t top off your tank when refueling.
8. Avoid using small gasoline engines like lawnmowers.
9. Use latex rather than oil-based paints and solvents.
10. Avoid using lighter fluid when grilling.
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