Whatever Happened to the Hole in the Ozone Layer?

In 1930, Thomas Midgley Jr., a mechanical engineer at General Motors, inhaled a lungful of chlorofluorocarbons (CFCs) and promptly blew out a candle. His experiment was an effort to show the American Chemical Society the safety of his new invention, a gaseous compound of chlorine, fluorine, hydrogen, and carbon that was an alternative to previous, toxic refrigerant gases like ammonia and sulfur dioxide. The emerging chemical was non-flammable, non-toxic, and would soon be in the homes of millions of American people.

That same year, General Motors and DuPont came together to create the Kinetic Chemical Company, a corporation that would produce Freon — a DuPont trade name for CFCs. By 1935, Frigidaire, General Motors, and DuPont had sold 8 million refrigerators that used Freon-12.  Due to their non-toxicity, CFCs became so popular in refrigerators and air conditioning units that city governments all over the U.S. named Freon the only coolant allowed for use in public buildings.

By the 1950s and 1960s, CFCs were found in a wide array of products due to their versatility. Properties such as being non-flammable, non-explosive, and non-toxic to humans allowed for CFC use in everything from Styrofoam to cleaning products to propellant in aerosols. It was also a cheap method for air conditioning homes and offices. At their peak use, CFCs were raking in about a billion dollars a year in the U.S.

But then two chemists at the University of California discovered that when CFCs were exposed to UV radiation, they became a major inorganic source of chlorine in the stratosphere, and this excess chlorine was leading to the destruction of the ozone in the stratosphere.

Made up of a high concentration of ozone gas, or O₃, the ozone layer is a region in the lower part of Earth’s stratosphere, the second layer of Earth’s atmosphere, and is responsible for protecting Earth from the strong ultraviolet radiation of the sun. Overexposure to UV radiation could lead to harmful effects for humans, such as skin cancer, weakened immune systems, and cataracts; it can also lead to reduced crop yield and food chain disturbances because of UV’s harmful effects on plant tissues and enzymes.

These findings led scientists to determine that holes had been created in the ozone layer, and the situation was getting worse every year. Researchers discovered the hole was largest over the Antarctic region due to certain chemical reactions and cold temperatures. Antarctic temperatures are an important factor because polar stratospheric clouds form when the temperatures drop below -108° F (-78° C). The ice crystals in these clouds, alternatively known as nacreous clouds, provide a surface where chlorine and bromine become highly reactive, and nitrogen, which regulates chlorine’s impact, is removed. When chlorine and bromine reach the ozone, they destroy its molecules; one chlorine atom can destroy over 100,000 ozone molecules, leaving holes in the ozone layer.

These effects made it clear: It would be crucial to regulate CFCs.

The phase-out of CFCs progressed swiftly, driven by widespread public awareness of the problem’s severity. This awareness was rooted in the dynamic environmental movement thriving in the United States at the time. The public consensus for action, a result of concerns about air and water pollution, pushed President Nixon to establish the Environmental Protection Agency in 1970. Alongside the creation of the EPA, landmark legislation like the Clean Air and Clean Water Acts were passed, continuing the wave of environmental activism. While Nixon was signing bills, grassroots organizations such as Friends of the Earth and the Sierra Club launched their first major campaigns focusing on protecting the ozone layer. They promoted boycotts of products containing CFCs, such as Styrofoam and aerosol sprays, to rally public support These efforts not only raised awareness in the U.S. but also inspired civil groups globally to pressure governments and businesses into action.

While the global protest was important, collaboration from companies that produced CFCs and the development of alternative chemicals were also critical. Because a small group of companies controlled global CFC production, it was easier to achieve agreement. The minor economic importance in combination with DuPont’s investment in other chemicals set the tone for the rest of the industry and allowed for the alignment of industry and government interests.

The global movement ultimately led to the Vienna Convention for the Protection of the Ozone Layer, a convention calling for the reduction of ODS — ozone-depleting substances. The agreement was negotiated from 1981 to 1985 and serve    d as a framework for the creation and signing of the Montreal Protocol in 1987. The Protocol, which was developed to advance the goals of the Vienna Convention, took effect in 1989. By 2008, it was the first and only U.N. environmental agreement to achieve universal ratification by 197 countries, every country in the U.N.

Since its establishment, around 99 percent of ozone-depleting substances have been phased out. In 1987, ozone-depleting substances hit a high of about 1.6 million tons of global emissions, with CFCs making up a little over one million tons. Now, global ODS emissions have dropped to nearly zero. While it’s taken several decades to see substantial improvement, the ozone hole started to heal in 2000. In 2021, the hole over Antarctica was the seventh smallest since recovery started in 1992.

Though the success is largely due to global cooperation and collaboration, it is also a result of amendments to the Montreal Protocol in the wake of new risks. In 2016, after a meeting in Kigali, Rwanda, the protocol was amended to reduce the use of hydrofluorocarbons (HFCs), a quick-fix substitute for CFCs. Eight years later, the United States finally became the 137th country to ratify this amendment.

Though the Kigali Amendment highlights the substantial progress made, the ozone hole requires a long time and ongoing compliance with the Montreal Protocol to heal. This protocol and the international environmental negotiations that permitted it serve as a reminder that regulation and multinational action can address environmental threats with rapid success. Precautionary work through the use of consumer boycotts and other organizing methods can lead to cooperation from companies and an overall change in the public’s consumer behavior.

The UN Environment Programme predicts that, if we stay the course, the Artic ozone hole will close by 2045 and the Antarctic ozone hole will close by 2066.