Dr. Fred Ask Dr. Fred


by Dr. Fred Bortz

Safesurf Rated All Ages

For more than twenty years, Dr. Fred Bortz worked as a scientist, researcher, and teacher. Now he spends most of his time writing books and articles for young readers like you.

He enjoys both science and writing for the same reason: HE LOVES QUESTIONS. He writes for people your age because he knows you love questions, too.

To find hot-links to other "Ask Dr. Fred" questions and learn how to send Dr. Fred your favorite question, go to the main "Ask Dr. Fred" page.

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Good Ozone; Bad Ozone

This "Ask Dr. Fred" question comes from an adult, Cheryl Menninger Wray of Hastings, Nebraska, mother of three, including a third grader at the time at Longfellow Elementary in Hastings whose science teacher, Mrs. Nancy Packard makes learning fun with creative hands-on projects and labs.

I understand that we have an alarmingly large hole (or thinning of the layer) in the ozone over Antarctica caused by human-made chemicals called chlorofluorocarbons (CFCs). On the other hand, we have way too much ozone down on the surface due to automobile emissions or other pollution makers. Why doesn't that ozone rise and replace what is missing above?

Why don't CFCs released into the atmosphere have any impact on the ozone down here? Why can't we just send high weather balloons full of ozone up into the atmosphere above Antarctica and release the ozone, rescue the balloon when it falls back down, fill it up again, and so on?

And why are CFCs still being manufactured? I know they are great for refrigeration, but isn't the need for an intact ozone layer of the greatest importance even to people who are just now getting refrigeration in their homes? Isn't there a useful alternative for CFCs yet? Or a way to bond them with something heavier so they wouldn't float up, yet would still be a good refrigerant?

Here is Dr. Fred's answer

Dear Cheryl,

This is a complex issue. Ozone is a molecule made of three oxygen atoms. Normal oxygen gas in the air has two oxygen atoms in its molecules. Ozone is the main eye-, nose-, throat-, and lung-irritating gas in "photochemical smog." That name tells a story. It combines "photo" (which comes from the Greek word for light) with "chemical" to describe the way smog is formed. You may know that "smog" is an invented word, a combination of smoke and fog.

Photochemical smog forms when ultraviolet (UV) rays from sunlight start chemical reactions among different polluting chemicals -- such as hydrocarbons, carbon monoxide, and oxides of nitrogen -- and the normal gases in the air auch as carbon dioxide, oxygen, nitrogen, and water vapor. UV light can break up normal oxygen molecules into two atoms, which we call free atomic oxygen. The free atomic oxygen can react with normal oxygen to form ozone. In the upper atmosphere, the UV light is very strong. Even though the ozone can sometimes break apart to form normal oxygen again, the powerful UV rays keep making more.

That ozone in the upper atmosphere is very important to us on the surface, because it absorbs a lot of the UV light. Since too much UV can be harmful to plants, animals, and humans, that ozone protects us from damage. Without it, people would suffer from much more skin cancer and a sight-stealing eye condition called cataracts.

We used to think that CFCs were safe, because they had no effect on living things. Although their main value is in refrigeration, we also used a lot of CFCs in spray cans. Several years ago we discovered that apparently harmless CFCs can cause major problems when they reach the upper atmosphere. There the strong UV light breaks them apart and releases free chlorine, which is a very reactive gas. The chemical reactions are too complex to describe here, but the result is less ozone in the upper atmosphere and less protection from UV for us on the ground.

Once that problem was discovered, the countries of the world wrote a treaty to stop making CFCs as soon as was practically possible. Eliminating them from spray cans was quick and easy. But refrigeration is very important for keeping foods fresh and safe to eat. We needed to find ozone-safe replacements for CFCs in refrigeration and air conditioning. Scientists and engineers are still working on that problem. They have made great progress. Some CFC replacements have been invented, but it will take a while before all refrigerators and air conditioners use them. In a few years, CFCs will no longer be made. In a few decades, they will no longer be in use anywhere in the world.

Although the ozone in smog is very irritating, there is not nearly enough to replace the ozone in the upper atmosphere. Smoggy areas are very small compared to the whole surface of the earth. Even if there was enough ozone in smog to help, sending it from the surface to the upper atmosphere would be difficult and very expensive. Ozone is heavier than air, so it tends to sink rather than rising. If we concentrated the ozone, we'd have to put it in tanks and use helium or hydrogen balloons to lift it.

Recent measurments of the protective ozone show that the thinning is continuing, but at a much lower rate than before the CFC treaty was signed. Scientific analysis predicts that the thinning will soon begin to be reversed. Your future is brighter because scientists discovered a problem and everyone in the world got together to solve it.

Scientifically yours,
Dr. Fred

Find Out More

Click here to find a great site about atmospheric chemistry. It comes from York University in Canada, and it has sections on both smog and the ozone hole.

Dr. Fred followed three of its links to other sites in Canada and England, and he liked them so much, he is including them here for you:

The Cambridge University "Ozone Hole Tour".

A British air-quality company's summary of the chemistry of atmospheric pollutants.

A Canadian document about smog called "Let's Clear the Air."

Click here for more "Ask Dr. Fred" questions.

Text copyright 2000-3 by Alfred B. Bortz, all rights reserved

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