Ozone

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Ozone (O3) is a chemical compound found in the upper layer of our atmosphere, as well as close to the ground. In the upper layer of the atmosphere, ozone helps to protect life by protecting our planet from the sun’s ultra-violet rays, but ground-level ozone is considered a pollutant and can harm human and plant health.

The Forest Health Index looks only at ground-level ozone. Measurements are drawn from local air quality stations that measure ozone and other harmful pollutants.