In the O-Zone

OK - take a deep breath, stretch your arms, and pay attention. I don't want you to "zone" out on me right now... Sorry for the bad joke; but let's talk about ozone. I am sure that you have heard of it, but what is it? Is it a good thing or a bad thing? The reality is that it is a little of both, depending on where it is.

Ozone is composed entirely of the element oxygen; three atoms worth. O₃ is a highly reactive and unstable form of oxygen that even at low levels can be irritating and toxic to organisms. It is formed naturally in the upper atmosphere, and can be formed at ground level by a lightning strike.

Ozone is a strong oxidizer (takes away protons) of many organic compounds and is used commercially to bleach oils, waxes, and textiles. It can also be used as a deodorizer, a germicide, and to sterilize water and air.

Ozone in the stratosphere (about six miles or 10 km above sea level) is good. Naturally, this area of the atmosphere contains about six parts per million of ozone molecules. The surrounding ozone absorbs a large amount of harmful ultraviolet (UV) light. UV light can damage your skin, and is why your mother probably smeared sun block all over you when you went swimming as a child.

Ozone near the ground is bad. It is very harmful to lung tissue, and for the reasons listed above is very harmful to plants and buildings. Ozone can accumulate at ground level from the reactions of light and chemicals produced by some industries and from car exhaust. On some days in some cities, the levels can get so high that it is hazardous to even go outside.