In the stratosphere, miles above the earth, ozone provides a
beneficial "umbrella" to protect life from harmful solar rays. However,
at ground level, ozone is harmful to breathe in high concentrations.
The
elderly, young children, and those with pre-existing respiratory
infections are particularly at risk from exposure to ground-level ozone,
but even healthy adults who spend a lot of time working or exercising
outdoors may be affected by high ozone levels. Symptoms of ozone
exposure include stinging eyes and throat, chest pains, coughing, and
breathing difficulty.