Q. I don't get it. Is ozone a good thing or a bad thing?

Ozone, a gas, is a form of oxygen. It is created when an electric spark or ultraviolet light passes through air, or when pollutants react chemically with sunlight.

Beneficial ozone is in the upper atmosphere, 10 to 30 miles above the surface of the Earth. It protects us from the sun's ultraviolet rays. Too much of these rays may increase the risk of skin cancer, cataracts and problems with our immune systems. Part of the good ozone layer has been destroyed by man-made chemicals.

Detrimental ozone is at ground level and is the main component of smog. This bad ozone is horrible for your respiratory system. Ozone may aggravate chronic lung diseases such as emphysema and bronchitis and reduce the immune system's ability to fight off bacterial infections in the respiratory system.

Seniors and children are especially vulnerable to ozone pollution. Those with asthma and nasal inflammations seem to be more sensitive to pollutants.

Active children are at highest risk from ozone exposure because they spend a lot of time playing outdoors. Obviously, adults who work and play outdoors are at higher risk than indoor types.

Ozone can make you cough, suffer from throat irritation and experience an uncomfortable sensation in your chest. This gas can also make it more difficult to breathe deeply.

People who experience high ozone levels may discover that their initial symptoms disappear after a while. However, ozone continues to cause lung damage even when there are no symptoms.

Studies done in the U.S. reported that ozone with concentrated ambient fine particles cause a significant increase in blood pressure. The studies also found that increased levels of ambient sulfate and ozone may increase the risk of heart arrhythmia in older people.

Seniors with respiratory problems should check the news and highway signs for reports of high ozone levels.

The Air Quality Index (AQI) reports levels of ozone and other common pollutants in the air. The higher the AQI value, the greater the health concern.

An AQI value of 0 to 50 is "Good." This range has no cautionary statement.

An AQI value of 51 to 100 is "Moderate." The cautionary statement is: "Unusually sensitive people should consider limiting prolonged outdoor exertion."

An AQI value of 101 to 150 is "Unhealthy for Sensitive Groups." The statement is: "Active children and adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion."

An AQI value of 151 to 200 is "Unhealthy." The statement is: "Active children and adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else, especially children, should limit prolonged outdoor exertion."

An AQI value of 201 to 300 is "Very Unhealthy." The statement is: "Active children and adults, and people with respiratory disease, such as asthma, should avoid all outdoor exertion; everyone else, especially children, should limit outdoor exertion."

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