Air Pollution Basics

What is Ozone?

Ozone is a molecule that serves both good and bad functions. In the lower atmosphere, the troposphere, ozone is a major component of smog. This is what people call "bad" ozone because of its harmful effects on people, materials and ecosystems. It is created when sunlight reacts with hydrocarbons and nitrogen oxides that are emitted by automobiles, auto body shops, gas stations, organic solvents and dozens of other sources. The concentration of ozone in the air also strongly correlates to many meteorological characteristics including temperature, wind speed and atmospheric stability.

Ground level ozone should not be confused with the protective ozone layer in the upper atmosphere, the stratosphere, that shields the Earth from the harmful ultraviolet rays of the sun. This is what people call "good" ozone. Over the past few years, scientists and the media have given a lot of attention to the problem of the "hole" in the ozone layer. In fact, "good" and "bad" ozone are chemically identical, it is only the location that makes the difference between the two. It is important that people do not mistake one for the other.

Click here to learn about the sources of ozone air pollution.

About Air Pollution Subcategories

Air Pollution Basics
• What is Ozone?
• Sources of Ozone
• Ozone Formation

Air Quality Facts

Health Effects of Ozone
• St. Louis Population with
Lung Disease
• How Healthy Adults are
Affected by Ozone
• Tips for Exercisers
• Ozone & Hospital
Admissions

Particulate Matter

Local Air Quality
• St. Louis Monitor Map

Air Quality Index

Air Quality Data