1.4.4. Ozone Pollution

Ozone occurs at ground-level naturally in low concentrations. The two major sources of natural ground-level ozone are hydrocarbons, which are released by plants and soil, and small amounts of stratospheric ozone, which occasionally migrate down to the earth's surface. Neither of these sources contributes enough ozone to be considered a threat to the health of humans or the environment. But the ozone that is a byproduct of certain human activities does become a problem at ground level. With more automobiles, and more industry, there's more ozone in the lower atmosphere. Tropospheric ozone is formed by the interaction of sunlight, particularly ultraviolet light, with hydrocarbons and nitrogen oxides, which are emitted by automobiles, gasoline vapors, fossil fuel power plants, refineries, and certain other industries.

High ozone levels usually occur during the warm, sunny summer months (from May through September). Typically, ozone levels reach their peak in mid to late afternoon. A hot, sunny, still day is the perfect environment for ozone pollution production.

Near the earth’s surface, ozone molecules damages forests and crops; destroys nylon, rubber, and other materials; and injures or destroys living tissue. It is a particular threat to people who already have respiratory problems.