In 2000, the American Lung Association initiated its State of the Air annual assessment to provide citizens with easy-to-understand summaries of the air quality in their communities based on concrete data and sound science. Air quality in counties are assigned a grade ranging from "A" through "F" based on how often their air pollution levels exceed the "unhealthful" categories of the U.S. Environmental Protection Agency’s Air Quality Index for ground-level ozone pollution. The air quality standard for ozone used as the basis for the report, 80 parts per billion averaged over an eight-hour period, was adopted by the EPA in 1997 based on the most recent health effects information. The grades in the report are assigned based on the quality of the air in areas, and do not reflect an assessment of efforts to implement controls that improve air quality. According to the most recent report, approximately 75 percent of the nation’s population live in counties with an "F" rating (where there are ozone monitors).

This figure is significant because ozone is a highly reactive gas that affects the respiratory system by severely irritating the mucous membranes of the nose and throat. Since 90% of the ozone breathed into the lungs is never exhaled, ozone molecules react with sensitive lung tissue which can cause several health consequences. Ozone's effects are more severe in individuals with preexisting respiratory disease. The length and frequency of exposure, as well as concentration, are significant factors in determining the many effects, which may include the following:

• Increased susceptibility to respiratory infection.
• Impaired lung function and reduced ability to perform physical exercise. (Recent studies suggest that healthy exercising individuals exposed to 120 parts per billion (ppb) of ozone for one hour experience significant shortness of breath. Similar decreases are also seen upon a 6 hour exposure to 80 ppb.)
• Increased hospital admissions and emergency room visits for respiratory diseases, which may be associated with exposures to one-hour ozone concentrations greater than 120 ppb.
• Severe lung swelling and death, due to short-term exposures greater than 300 ppb.

Activity level (e.g. moderate-heavy exercise) and environmental stress (e.g. humidity and high temperatures) also affect susceptibility. Other factors include:

• Individual sensitivity.
• Age (children and young adults appear to be more sensitive than older adults).
• Smoking status (smokers appear to be less sensitive than non-smokers).
• Chronic obstructive pulmonary disease or asthma, which may increase susceptibility to ozone-induced decreases in lung function. (Decreases in lung function are greater in asthmatics concurrently exposed to ozone and pollen than for either pollutant alone.)
• Possibly additive or synergistic effects when ozone combines with sulfur dioxide, nitrogen dioxide, carbon monoxide, sulfuric acid, or other particulate aerosols.

To avoid prolonged exposure to ozone, people could:

• Reduce the amount of time spent outside on days when high levels of ground level ozone are present.
• Decrease involvement in activities that require heavy exertion, or substitute another activity that requires more moderate exertion (e.g., go for a walk rather than a jog). Examples of activities that involve moderate exertion include climbing stairs, playing tennis or baseball, simple garden or construction work, and light jogging, cycling, or hiking. Activities that involve heavy exertion include playing basketball or soccer, chopping wood, heavy manual labor, and vigorous running, cycling, or hiking.
• In addition, plan outdoor activities when ozone levels are lower, usually in the morning or evening.

In this lesson, students will investigate America's 25 Most Ozone-Polluted Counties, Counties with No Monitored Ozone Air Pollution in Unhealthy Ranges, and the air pollution levels in their own state. Students will compare the data and determine if they should be concerned about the air they breathe.
 

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