Ozone, one of the most common air pollutants, is created by a combination of sunlight, light winds, hydrocarbons from burned fuel and nitrogen oxide. Man-made air pollutants come from motor vehicles and power stations. This combination of elements can create a smog cloud. It is most common in cities where automobile concentration is greatest, and in the summer when the right conditions of sunlight and low winds occur. Under these conditions, we become literally surrounded by an ozone cloud.
Ozone triggers asthma because it is extremely irritating to the lungs and airways.
It is well established that ozone concentration is directly related to asthma attacks, need for increased doses of asthma drugs, and emergency treatment for asthma. Throughout the United States, Ozone Action Days are declared when concentrations are highest. These declarations alert people with asthma to avoid the smog as much as possible by remaining in air-conditioned places and by taking other measures to avoid irritants and allergens. During Ozone Action Days, people with asthma should limit their time outdoors, especially from 11 a.m. to 8 p.m. Most of all, do not exercise outdoors on Ozone Action Days.