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JAMA Patient Page |

Health Effects of Ozone FREE

Sharon Parmet, MS, Writer; Cassio Lynm, MA, Illustrator; Richard M. Glass, MD, Editor
JAMA. 2003;290(14):1944. doi:10.1001/jama.290.14.1827.
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Ozone is a colorless gas that can be found in the upper atmosphere about 20 to 30 miles above the earth where it acts as a protective shield. Ozone prevents some of the sun's cancer-causing ultraviolet rays (rays with a wavelength between that of visible light and x-rays) from reaching the earth's surface. But when ozone forms near the surface of the earth, it can be harmful. If ozone is breathed in, it reacts with the tissues of the lung and can cause symptoms. When ozone levels are high, individuals with asthma often experience a harder time breathing, may have more asthma attacks, and need to use more medications. The October 8, 2003, issue of JAMA includes an article on the health effects of ozone among children with asthma.

Ozone is formed through chemical reactions involving hydrocarbons and nitrogen oxide (types of pollution) and sunlight on calm summer days. Ozone peaks in the middle of the day throughout the summer months and is worse in cities with high levels of pollution or smog. Children who spend lots of time playing outside, persons with asthma, and elderly individuals are most at risk of the effects of ozone.


  • Irritation of the eyes, nose, and throat

  • Headaches

  • Difficulty taking a deep breath

  • Increased need for asthma medications


  • Minimize your exposure to ozone by staying indoors during peak ozone hours, usually afternoons on sunny summer days.

  • If you exercise outside, minimize your ozone exposure by exercising before 11 AM or after 8 PM.

  • Listen to your local weather report for "ozone action days" days that exceed safe levels of ozone. Try to stay inside as much as possible on ozone action days.



To find this and other JAMA Patient Pages, go to the Patient Page link on JAMA's Web site at http://www.jama.com. Many are available in English and Spanish.

Sources: US Environmental Protection Agency, American Lung Association, United Nations Environment Program

The JAMA Patient Page is a public service of JAMA. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JAMA suggests that you consult your physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. Any other print or online reproduction is subject to AMA approval. To purchase bulk reprints, call 718/946-7424.




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