The Mysterious Return of Ozone-Depleting CFCs

CFCs, the harmful ozone-depleting chemicals banned back in the 1980s, are experiencing a mysterious comeback. Who is the new producer, in violation of the international agreement?

Sabrina Stierwalt, PhD ,
June 25, 2018
Episode #291

Avid Everyday Einstein listeners may recall that the depletion and subsequent rebound of the ozone layer is one of my favorite science stories. Scientists were able to identify a problem (the depletion of the ozone layer) and its cause (chlorofluorocarbon gases or CFCs) and within two years, politicians took swift action to reverse course to protect our planet and its inhabitants. The ozone layer has now rebounded and scientists predict that by 2060-2075, the ozone layer will be back to its pre-1950 levels. Science truly can change the world.

Unforutnately, CFCs are making a comeback in the atmosphere and scientists are not sure where they are coming from. Let’s take a look at how we know they have returned and what the leading theories are to suggest why.

What Are CFCs?

First, we cannot tell the story of ozone depletion and CFCs without highlighting the incredibly important work of Mario Molina, a Mexican immigrant to the United States. Molina was born in Mexico City and is now a Distinguished Professor of Chemistry and Biochemistry at the University of California, San Diego. Together with his former postdoctoral advisor at the University of California, Irvine, Sherwood Rowland, Molina was awarded the Nobel Prize in Chemistry for his discovery that chlorofluorocarbon gases (CFCs) contribute significantly to depletion of the ozone layer which protects us Earth inhabitants from cancer and cataract-causing harmful UV rays.

In the 1970s, CFCs were commonly used in refrigeration and as a propellant in aerosol sprays and were sold under the brand name Freon. Manufacturers first turned to CFCs because they were inflammable and nontoxic and cheap to produce. CFCs are relatively stable molecules so, once released, they almost always make their way upwards to live a long life in the Earth’s stratosphere.

However, in 1974, Molina and Rowland noted that, once in the stratosphere, CFCs become vulnerable to ultraviolet radiation from the sun which breaks them down into their constituent parts, including chlorine, fluorine, and carbon atoms. Those chlorine atoms react with oxygen atoms in the atmosphere which leads to the destruction of the molecules that make up the ozone layer. About 10 years later, a trio of British scientists found evidence of this depletion in action.

Science is a global pursuit that benefits from the free exchange of ideas and the promotion of collaboration. Mario Molina’s work is just one example of how an openness to immigration contributes to the United States’ status as a leader in scientific research. In fact, of the 78 Nobel Prizes awarded to scientists in the U.S. in chemistry, medicine, and physics since 2000, 39% were awarded to immigrants. And this is not just a trend for well-established, senior scientists. According to a study by the National Foundation for American Policy, over 80% of recent finalists in the Intel Science Talent Search (a science competition often dubbed the “Junior Nobel Prize”) were the children of immigrants.


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