Even healthy people exercising outdoors can experience breathing problems when exposed to ozone. Ozone levels become unsafe when they exceed health standars. Just a single hour of exposure to high levels of ozone can cause reactions like shortness of breath, coughing, headaches, nausea and respiratory discomfort. Plants suffer the effects of ozone too. It can reduce plant yields and affect the quality of crops such as corn, wheat and soybeans, making them less valuable on the market.
Ozone also corrodes man-made materials such as textiles and rubber.