Student Features

Ozone: Friend and Foe
Does your city or town have "bad air" days in the summertime? Are you told to wear sunscreen when you go out to play? The same gas -- ozone -- that causes bad air also protects us from the Sun's harmful effects. How can one gas be both good and bad?
Image above: Drawing of the Aura satellite orbiting Earth. Credit: NASA

Some of the ozone in our air is just part of Nature. But human beings make extra ozone every day. Ozone forms near the ground due to fumes from cars, trucks, factories and lawn mowers. The fumes react with sunlight to make ozone. This happens most during the late spring and summer.

Ozone near the ground can bother our lungs and make it hard to breathe. In some places bus rides are free and people are asked to carpool on high ozone days. This lowers the number of vehicles on the street. People are also asked to wait until the Sun goes down to mow lawns or fill gas tanks.

But we wouldn't want to get rid of ozone entirely. The natural ozone that is found high up in the sky blocks the Sun's UV light. UV light can cause sunburn, skin cancer and eye damage.
Ozone hole
Image above: View of the South Pole from NASA's TOMS (Total Ozone Mapping Spectrometer) satellite. Blue and green indicate relatively large amounts of ozone. Red and yellow mark the "ozone hole", an area of decreased ozone. Credit: NASA

Some of the things we use can harm the ozone. For example, air conditioners and refrigerators produce chemicals that destroy ozone. Each fall an area of low ozone forms over the South Pole. This "ozone hole" lets a lot of UV light through.

NASA is about to launch a new satellite into space. It's called "Aura." Aura will measure ozone and many other gases on Earth. And it will also be able to see smoke and dust. And it will track chemicals that produce ozone.

How can you reduce the amount of ozone near the ground? Walk or ride a bike instead of going in a car. The fewer vehicles on the road, the less "bad" ozone there will be in our air.

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Stephanie Stockman, NASA Goddard Space Flight Center
Adapted with permission from Celebrating Chemistry, a publication of the American Chemical Society, © Copyright 2003
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