Ozone is a reactive and irritating chemical. When inhaled, it can irritate and inflame the airways, the passages that carry air from the mouth and nose to the lungs.

At low levels, this may not cause any noticeable symptoms, but may inflame the airways and decrease air flow. At higher levels, symptoms can include shortness of breath, coughing, wheezing, and chest tightness or pain. People who are exercising outdoors may find that their stamina is diminished.

Particle Pollution

When exposed to particle pollution, people with heart and lung diseases and older adults are more at risk of hospital and emergency room visits, or, in some cases, even death. These effects have been associated with both short-term (as short as one hour) and long-term exposures.

Particles can aggravate heart diseases such as congestive heart failure and coronary artery disease. Particle pollution has also been associated with cardiac arrhythmias and heart attacks.

Particles can aggravate lung diseases such as bronchitis, causing increased medication use and doctor visits. Particles can also increase susceptibility to respiratory infections.

Many scientific studies have demonstrated the effects of ozone and particle pollution. With higher levels of ozone, people report more respiratory symptoms, use more respiratory medications, make more emergency room visits, and are hospitalized more. When particles aggravate heart and lung conditions, many of the same implications occur. Most importantly, particle pollution is linked to other serious health risks -- including death from heart and lung disease.