Ozone is like cholesterol—there is good ozone and bad ozone—it all depends on location. In the earth’s upper atmosphere, ozone occurs naturally and protects us by shielding the surface from the sun’s harmful rays. In the lower atmosphere, ozone is formed when pollutants react chemically in the presence of sunlight.
Summer means more sunlight and more bad ozone. Bad ground-level ozone can make it harder to breathe—especially for people with asthma. Everyone (including people without asthma) should be conscious of their exposure.

When local newscasts warn of high ozone levels, they are referring to ground levels. Ground-level ozone can cause coughing and irritation in the throat and chest, making breathing shallow and labored. This can lead to inflammation and temporary damage to the lining of the lung.
High ozone levels can occur anywhere, but certain environmental characteristics can make it worse. “Areas with heavy automobile traffic, those that are prone to heat inversions (hot air that traps pollutants near the ground), and places that get a lot of sun are more likely to experience high ozone levels,” says David Peden, MD, a Fellow of the American Academy of Allergy, Asthma and Immunology (AAAAI) and Chair of the AAAAI’s Environmental Control and Air Pollution Committee.

Ground-level ozone can affect anyone, but asthmatics are more sensitive. “Many studies show that during ozone alerts, asthmatics tend to have attacks that require more frequent use of medication, a doctor’s care, or even hospitalization,” Peden says. “Ozone also can increase asthmatics’ sensitivity to allergens, which can trigger allergy and asthma attacks.” Airborne allergens include pollens, molds, dust mites, cockroaches, and animal dander.

In addition to aggravating asthma, ozone can affect other chronic lung diseases such as emphysema and bronchitis. It also may increase the risk of respiratory infections.

The AAAAI encourages everyone, especially those with asthma and other respiratory diseases, to take extra precautions during the hazy, hot, and humid summer days that foster high ozone levels. Paying attention to air quality reports is a good first step. During the summer ozone season, this information is often reported in newspapers, weather forecasts, and on Web sites. Parents of asthmatics should make certain that camp counselors, coaches, teachers, and other caregivers have ready access to medications on high ozone days and follow the appropriate preventive measures.

“The best way for asthmatics to reduce flare-ups is to use prudent common sense,” Peden advises. “They should avoid spending a lot of time outdoors during peak ozone times, especially when exercising, and work with their allergist to create a good long-term asthma management plan that treats the underlying airway inflammation, which is the root cause of asthma.”

The only way to combat the adverse effects of high ozone levels is with an environmental approach, experts agree. “There is no specific asthma treatment for high ozone,” says Stephen Wasserman, MD, University of California, San Diego, past president of AAAAI. “Most people in the United States do not spend more than 15 minutes outdoors each day, so much of the time, high ozone is not a problem. External air pollution is much less a trigger for asthma than indoor allergens.”

Greg Thompson is associate editor of RT Magazine.