Q:  OZONE ... Which ozone is good and which is bad?

OZONE (Molecular Formula: O₃)

A:    There is good ozone and bad ozone.

Ground-level ozone, the primary component of smog, found in the earth's atmosphere (tropospheric ozone) is "bad ozone". Ozone is formed in our atmosphere as a result of complex reactions involving air pollutants from industrial, vehicular, chemical, and consumer products (e.g. hydrocarbons and nitrogen oxides) and ultraviolet radiation from sunlight (view ozone movie). When inhaled, even at low levels, ozone can cause acute respiratory symptoms, such as coughing and discomfort in the throat and chest; aggravate asthma; damage your lung's capacity to transfer oxygen to the body; inflame and damage lung tissue; and impair the body's immune response to respiratory infection. Children, especially those with asthma, are at the greatest risk from ozone pollution. During the summer, when ozone concentrations are highest, children playing outside are most likely to experience respiratory symptoms and effects.

So what is good ozone? Ozone in the stratosphere, which lays 25 to 30 miles above the earth, blocks harmful ultraviolet light emitted from the sun. Ultraviolet light can cause cataracts and certain skin cancers, warming of the earth's surface, and damage to plants and oceanic plankton. The stratospheric ozone layer serves as a protective filter against this type of radiation and is therefore considered "good ozone". Halogenated chemical solvents, halon fire retardants, and freon refrigerants (chemicals containing chlorine, flourine, or bromine atoms) are believed to be responsible for stratospheric ozone depletion (ozone hole). Environmental regulations attempt to eliminate or control the production and use of stratospheric ozone-depleting substances and lay out provisions on safe substitutes for these important substances.

    Remember, "Good Up High - Bad Nearby"

Go To On the Trail of the Missing Ozone at EPA's Explorers Club (large pdf file) 

Go To Consumer Products and Smog at ARB's Web Site

Go To Fact Sheets, Brochures, and Presentations at ARB's Web Site