Both urban and rural areas can have high ozone levels, depending on wind speed, direction and the lay of the land. Elderly individuals, people with existing respiratory ailments, such as asthma and emphysema, and young children should avoid strenuous outdoor activity on Ozone Action Days. Even healthy adults exercising or working outdoors may experience lung problems on high ozone days. Plants, also suffer the effects of ozone. It can reduce plant yields and affect the quality of crops, making them less valuable on the market.
Ozone also corrodes man-made materials such as textiles and rubber.
The Delaware Valley has made great strides in improving the region's air quality. However, there are still many days each summer when the Philadelphia region exceeds the federal health-based ozone air quality standard. If we continue to violate these standards, businesses and individuals may be required to spend more on emissions controls. The Ozone Action program is entirely voluntary and depends on everyone to share the responsibility. Since the weather influences the formation of ground-level ozone, high ozone days can be predicted.