Children. Kids at play spend many hours out-of-doors in the summertime in often vigorous activities. Asthma is common in children as well.

Active Adults. Healthy adults of all ages who exercise or engage in vigorous outdoor work are also sensitive to ozone as they breathe in larger volumes of air than inactive persons. Also when working or exercising, persons inhale more deeply and more often than when inactive.

Persons with Respiratory diseases. Asthma and other respiratory diseases make the lung more vulnerable to the effect of ozone. Persons with respiratory diseases often feel the effects of ozone at lower concentrations and sooner than persons without respiratory diseases.

Ozone can aggravate asthma. When ozone levels are high, more asthmatics may have attacks that require medication or a visit to the doctor. Ozone can make people more sensitive to allergens such as dust mites, fungus, pollen and pet dander that cause asthma attacks. Also asthmatics are more severely affected by reduced lung function and irritation directly caused by ozone exposure.

Lung Damage. Ozone can damage the lining of the lung. Similar to a sunburn on the skin, ozone exposure can inflame cells that line the lungs. Within a few days, the cells die and are discarded much like a sunburn can cause peeling skin. Repeated damage can permanently alter the lung. Ozone is suspected to cause other health effects such as aggravating chronic lung diseases such as emphysema and bronchitis or reduce the immune system.