Submitted for your consideration: a blue, pungent gas that used to be simple oxygen –but now is something quite different. You are about to enter…the O-Zone.

Ozone, at first gasp, doesn’t seem like something to be concerned about. Normal oxygen molecules–the ones we breath–consist of two oxygen atoms. Add one more, and you get ozone. So it’s really just a form of oxygen–but that extra atom makes all the difference.

Ozone forms in a number of ways. High-voltage electrical discharges create it; you can smell it around an arc-welder, or if you’re uncomfortably close to a lightning strike. Ozone also forms by the action of sunlight on hydrocarbons and nitrogen oxides–in other words, car exhaust. As a result, it’s a major pollution problem in urban centres. (A recent study by Environment Canada indicates that in the summer more than half the Canadian population is regularly exposed to ozone concentrations at levels known to affect health.)

High ozone levels can cause eye irritation, decreased lung function and premature aging of lung tissue, worsen the symptoms of respiratory illness, and retard the growth of plants.

Yet potentially far more serious than too much ozone at ground level is a lack of ozone 10 to 50 kilometres above it. This is where the ozone layer forms–and, unfortunately, unforms.

The ozone layer is important because it acts as a sunscreen for the entire Earth, protecting us from the ultraviolet radiation of the sun. That radiation is powerful enough, at high altitudes, to split regular oxygen molecules into single oxygen atoms, some of which reform as ozone–which in turn breaks down, re-forms as oxygen, and dissociates again. All this takes energy, which is absorbed from the ultraviolet radiation, thereby weakening it. The ozone itself also absorbs some of the ultraviolet.

Of course, some ultraviolet does get through, and always has–a good thing, since it provides energy for the synthesis of Vitamin D in our skin. It also causes pale-skinned people to suntan. However, too much ultraviolet is dangerous. Suntans become sunburns, and like other kinds of radiation, ultraviolet can cause genetic damage to skin cells, which can eventually lead to cancer. High levels of ultraviolet radiation have also been linked to cataracts, weakened immune systems and crop damage.

All of this would be academic, thanks to the ozone layer, if it weren’t for the troubling fact that something has been destroying that protective layer, especially over Antarctica and, to a lesser extent, over the Arctic.

Every spring (our autumn), a temporary “hole” opens in the ozone layer over the Antarctic as ozone levels drop by up to 50 percent. In 1989 that “hole” was twice as big as the entire continent.

This doesn’t mean a giant hole in the ozone is about to engulf the entire planet: Antarctica’s hole is held in place by a persistent vortex of winds circulating the continent. However, ozone depletion on a lesser scale has been detected in the Arctic, where there is no vortex to keep it in place. As a result, the ozone-poor air disperses shortly after it forms–which may account for low-ozone readings noted in recent years above Sweden.

Despite being confined, the Antarctic hole can also affect populated areas. In 1987 when the hole broke up, clumps of ozone-depleted air flowed over Australia. Ultraviolet levels in the southern part of that continent climbed by 20 percent for a few days, and the average for the entire month was 14 percent higher than normal.

Some of this annual ozone depletion is probably natural in origin. What worries researchers is the part that isn’t. Studies show that the ozone hole in Antarctica is accompanied by chlorine and fluorine compounds. There are natural sources of chlorine–volcanoes, for example–but all the fluorine in the atmosphere is man-made, which probably means a lot of its accompanying chlorine is, too.

The culprit is almost certainly those now-infamous compounds known as chlorofluorocarbons (CFCs), used to form bubbles in some kinds of plastic foam, as the coolants in refrigerators and air-conditioners, to clean microchips, and, in many parts of the world, as aerosol propellants.

CFCs are extremely stable, but ultraviolet radiation destroys them, releasing atoms of chlorine which form compounds with ozone. Worse, a single CFC molecule can set up a chain reaction that destroys several hundred thousand molecules of ozone.

Steps are being taken now internationally to reduce the use of CFCs–approximately 50 nations have signed a protocol calling for a total ban on CFC production by the end of the century–but because they break down slowly, the CFCs already in the atmosphere will go on causing damage for decades.

So it looks as if, like it or not, we’re in the middle of a long-term, poorly planned experiment involving our atmosphere, and stopping it isn’t going to be easy–or maybe even possible.

Such is life in the O-Zone. Rod Serling would feel at home–except, unlike his Twilight Zone, this Zone we can’t escape by changing channels.

Permanent link to this article: https://edwardwillett.com/1991/07/ozone/

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