How Was the Ozone Layer Being Depleted?

nontoxic CFC chemicals harm protective layer of oxygen compound

By Jonny Lupsha, Wondrium Staff Writer

A U.N.-backed report said the ozone layer is once again healing. The protective band of ozone had been depleting since the 1950s but has since been healing, intermittently. Why does the ozone layer matter?

Aerial view of Earth and it's atmosphere
CFCs released in the atmosphere drift up to the stratosphere and deplete the ozone layer when they undergo a chemical reaction due to the ultraviolet radiation of sunlight. Photo by Vladi333 / Shutterstock

Concerns over the ozone layer date back to the early 1970s, when scientists demonstrated that it could be depleted by certain chemicals—and already had been for some time. The public was warned about this environmental concern and it became ingrained in the social conscience even without everyone fully understanding it.

These days, the weakened ozone layer is on the path to restoration thanks to regulations being placed on various 20th-century chemicals. A recent report said that rogue emissions of a refrigerant chemical used in China have been stopped and the ozone will return to pre-1980 levels by 2040.

What’s the big deal with the ozone layer? In his video series The Joy of Science, Dr. Robert M. Hazen, Clarence J. Robinson Professor of Earth Sciences at George Mason University, explains why the ozone layer matters.

What Is the Ozone Layer?

“It’s not really a layer; it’s just a region of the atmosphere about 35 kilometers up, a thick band in which there’s a slightly increased concentration of the molecule ozone,” Dr. Hazen said. “Ozone is O3, three atoms of oxygen bound together, and it only comprises a small fraction of the percent of the atmosphere at that level; most of the atmosphere is still nitrogen and oxygen.”

Despite being in such trace amounts, this added ozone protects us from the Sun’s UVB rays, which are the same ultraviolet rays that cause sunburn. Don’t we still get sunburned anyway? Yes, but, much like a pair of sunglasses tints the world in front of your eyes but still lets you see, the ozone lessens the amount of ultraviolet rays getting through. Too much of ultraviolet radiation is harmful to plant growth and other life on Earth’s surface.

How Did the Ozone Layer Get Depleted?

The problem of the thinning ozone layer dates to the 1950s when cheap, nontoxic chemicals, called chlorofluorocarbons or CFCs, were introduced to the market to be used in the production of refrigerators.

“They were also used for aerosols; they were used for other everyday applications, for cleaning surfaces, and so forth,” Dr. Hazen said. “Production of the gas freon, which you may have heard of, and other CFCs quickly grew into a major chemical industry. There seemed to be many benefits, because these were nontoxic gases, and there didn’t seem to be a downside at all to CFCs.”

Concerns about CFCs were first raised in 1970 by a Dutch chemist who demonstrated that ozone could be depleted by chemical reactions with nitrogen oxides. A few years later, American scientists showed that CFCs caused rapid destruction of ozone through a few simple chemical reactions. How?

“What happens, high in the atmosphere, is that you have normally stable CFC molecules, but they’re fragmented by ultraviolet light—the very ultraviolet light that ozone absorbs,” Dr. Hazen said. “When they’re fragmented, it triggers the release of single, highly reactive chlorine atoms. If a chlorine atom comes in contact with ozone, the ozone’s going to be split into two pieces: an O2 molecule and a ClO molecule.

“This breaks down the ozone.”

Since the 1980s, more than 100 ozone-depleting compounds have been banned. The ozone holes over the Arctic and Antarctica should be repaired by 2045 and 2066, respectively.

The Joy of Science is now available to stream on Wondrium.

Edited by Angela Shoemaker, Wondrium Daily