Ozone is a gas. It can be good or bad, depending on where it is. "Good" ozone occurs naturally about 10 to 30 miles above the Earth's surface. It shields us from the sun's ultraviolet rays. Part of the good ozone layer is gone. Man-made chemicals have destroyed it. Without enough good ozone, people may get too much ultraviolet radiation. This may increase the risk of skin cancer, cataracts, and immune system problems.
"Bad" ozone is at ground level. It forms when pollutants from cars, factories, and other sources react chemically with sunlight. It is the main ingredient in smog. It is usually worst in the summer. Breathing bad ozone can be harmful. It can cause coughing, throat irritation, worsening of asthma, bronchitis, and emphysema. It can lead to permanent lung damage, if you are regularly exposed to it.
Environmental Protection Agency
- You Can Help Keep the Air Cleaner -- Every Day (Environmental Protection Agency)
- Greenhouse Gases (National Oceanic and Atmospheric Administration)
- Ozone Air Purifiers: Can They Improve Asthma Symptoms? (Mayo Foundation for Medical Education and Research)
- Ozone Generators That Are Sold as Air Cleaners (Environmental Protection Agency, Indoor Environments Division)
- ClinicalTrials.gov: Ozone Exposure (National Institutes of Health)