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HEALTH EFFECTS OF OZONE
The American Lung Association has chosen ozone as the focus of the State of the Air reports because it is one of the most damaging and most pervasive of the common outdoor air pollutants. Ozone poses health dangers for millions of people in the United States, in both big and small metropolitan areas.
Dangers of Ozone
Ozone is an intensely irritating gas. Ozone is the main component of the air pollution known as smog. Ozone reacts chemically ("oxidizes") internal body tissues that it comes in contact with, such as those in the lung.
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As noted at the beginning of this report, ozone, at levels commonly found in the air in many American cities during summer months, can damage the lungs and airways, causing them to become inflamed, reddened and swollen. This response can cause coughing, burning sensations and shortness of breath. Ozone increases the risk of asthma attacks in people with asthma. |
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The evidence about the damaging health effects of ozone continues to mount. Much research has been conducted about ozone since 1997, the last time the Environmental Protection Agency reviewed the ozone standards. The Clean Air Act requires that the standards be reviewed every five years, so it is imperative that the EPA review the standards to consider the wealth of new information that has accumulated in the last six years.
Research on the effects of prolonged exposure to relatively low levels of ozone has found reductions in lung function, inflammation of the lung lining and breathing discomfort. In studies of animals, ozone exposure has been found to increase susceptibility to bacterial pneumonia infection.
One study of 16 Canadian cities over a 10-year period found that air pollution, including ozone, at relatively low concentrations, is associated with excess admissions to the hospital for respiratory diseases. 2
Ozone levels generally rise from May through September when higher temperatures and the increased amount of sunlight combine with the stagnant atmospheric conditions that are associated with ozone air pollution episodes.
In recent years, scientists have begun to focus on the effects of long-term, repeated exposure to high levels of ozone. A study of college freshmen who were lifelong residents of California found a strong relationship between lifetime ozone exposure and reduced lung function.3 Additional evidence of shorter term effects comes from a study of 72 cadets at the U.S. Military Academy at West Point, who attended a summer training program in which they spent an average of 11 hours a day outdoors. The study found that the 21 cadets who attended summer training in Fort Dix, New Jersey, an area with elevated ozone levels, had a larger drop in lung function over the summer, compared with the cadets who trained at sites in Georgia, Missouri and Oklahoma with lower ozone levels.4
High ozone levels are particularly dangerous for people with asthma. When ozone levels are high, more people with asthma suffer asthma attacks that require a doctor’s treatment or use of extra medication.
Children at Special Risk
A number of recent studies have added to the evidence that children are especially vulnerable to the harmful effects of ozone. Children spend significantly more time outdoors, especially in the summertime when ozone levels are the highest. Children also spend more time exercising, which causes them to breathe in more air, and therefore bring more pollution deep into the lungs.
A new study increases evidence that ozone negatively affects the growth of lung function in children. The four-year study followed 1,600 southern California children enrolled as fourth graders in 1996. 5 The researchers found that the children’s exposure to ozone was correlated with reduced growth in peak flow rate—the ability to push air out of the lungs, which is an indicator of growth in lung function. Larger deficits in lung function growth rate were observed in children who spent more time playing outdoors, confirming
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