Ozone is a noxious form of oxygen.
Unlike ozone in the stratosphere which protects us from ultraviolet radiation, ground level ozone can cause lung damage. Elderly individuals, people with existing respiratory ailments such as asthma and emphysema, and young children should avoid strenuous activity on Ozone Action Days. Even healthy adults exercising or working outdoors may experience lung problems on high ozone days. The objective of the Ozone Action program is to decrease the formulation of ground level ozone during the summer. The program warns the public about forecasted high ozone days, and asks for voluntary actions to reduce emissions of ozone-forming pollutants.